Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Abstract

Background

Aspiration pneumonitis is a syndrome resulting from the inhalation of gastric contents. The incidence in obstetric anaesthesia has fallen, largely due to improved anaesthetic techniques and the increased use of regional anaesthesia at caesarean section. However, aspiration pneumonitis is still a cause of maternal morbidity and mortality, and it is important to use effective prophylaxis.

Objectives

To determine whether interventions given prior to caesarean section reduce the risk of aspiration pneumonitis in women with an uncomplicated pregnancy.

Search methods

We searched the Cochrane Pregnancy and Childbirth Group’s Trials Register (April 2009).

Selection criteria

Randomised controlled trials were included. Quasi-randomised trials were excluded.

Data collection and analysis

Authors independently assessed the studies for inclusion, assessed risk of bias and carried out data extraction. Data entry was checked.

Main results

Twenty-two studies, involving 2658 women, are included, all having a caesarean section under general anaesthesia. The studies covered a number of comparisons, but were mostly small and of unclear or poor quality.

When compared to no treatment or placebo, there was a significant reduction in the risk of intragastric pH < 2.5 with antacids (risk ratio (RR) 0.17, 95% confidence interval (CI) 0.09 to 0.32, two studies, 108 women), H₂ antagonists (RR 0.09, 95% CI 0.05 to 0.18, two studies, 170 women) and proton pump antagonists (RR 0.26, 95% CI 0.14 to 0.46, one study 80 women). H₂ antagonists were associated with a reduced the risk of intragastric pH < 2.5 at intubation when compared with proton pump antagonists (RR 0.39, 95% CI 0.16 to 0.97, one study, 120 women), but compared with antacids the findings were unclear. The combined use of ’antacids plus H₂ antagonists’ was associated with a significant reduction in the risk of intragastric pH < 2.5 at intubation when compared with placebo (RR 0.02, 95% CI 0.00 to 0.15, one study, 89 women) or compared with antacids alone (RR 0.12, 95% CI 0.02 to 0.92, one study, 119 women).

Authors’ conclusions

The quality of the evidence was poor, but the findings suggest that the combination of antacids plus H₂ antagonists was more effective than no intervention, and superior to antacids alone in preventing low gastric pH. However, none of the studies assessed potential adverse effects or substantive clinical outcomes. These findings are relevant for all women undergoing caesarean section under general anaesthesia.

BACKGROUND

Description of the condition

Aspiration pneumonitis was first described by Mendelson in the 1940s (Mendelson 1946). It occurs when gastric acid gains access to the lungs in the absence of a cough reflex. Although rare, during anaesthesia for caesarean section, aspiration pneumonitis is still a cause of maternal mortality even in well-resourced countries such as the United Kingdom (CEMD 2001). Aspiration pneumonitis is largely associated with general anaesthesia, with passive regurgitation of gastric contents being the main risk factor. In contrast, vomiting is an active process and is not necessary for aspiration to occur. As regional anaesthesia is now used more frequently for caesarean section, the incidence of aspiration pneumonitis is very rare. However, prophylaxis against acid aspiration (also known as gastric aspiration) and aspiration pneumonitis is still important as there will be situations that require general anaesthesia for caesarean section (for example, emergency caesarean section or where regional anaesthesia has failed or is contraindicated). Restricting food and fluids in labour is another intervention aimed at reducing the risk of aspiration pneumonitis; however, evidence on the effectiveness of this is covered in another Cochrane review (Singata 2002).

Description of the intervention

Several different types of drugs have been used to reduce the risks and effects of acid aspiration. These include antacids, H₂ receptor antagonists, proton pump inhibitors and prokinetic drugs, either alone or in combination. This wide range may reflect the absence of an ideal regimen (Grieff 1994; Sweeney 1986; Tordoff 1990).

How the intervention might work

Antacids

Antacids (such as sodium citrate) are alkaline agents used to directly neutralise gastric acid. Antacids are often given just prior to induction of general anaesthesia, and while they increase intragastric pH, they also increase intragastric volume, and may cause more harm than benefit (Bond 1979). It is possible that aspiration of antacid solutions may also cause lung damage. Non-particulate antacids (such as sodium citrate) are thought to be less likely to increase the risk of severe pneumonitis compared to particulate antacids (magnesium trisilicate) should aspiration occur (Gibbs 1979).

H₂ receptor antagonists/inhibitors

H₂ receptor antagonists (such as ranitidine) act by inhibiting the secretion of acid into the stomach which reduces both the volume and acidity of the stomach contents (Thwaites 1999).

Proton pump antagonists

Proton pump antagonists (such as omeprazole) act by blocking the production of stomach acid by interfering with the pump which secretes protons (acid) into the stomach (Browne 1993).

Prokinetic drugs

Prokinetic drugs increase gastric motility and therefore accelerate gastric emptying and reduce gastric volume. The most commonly used prokinetic drug is metoclopramide which may also act as an anti-emetic (Cohen 1984).

Nasogastric tube aspiration

Nasogastric aspiration or suction is the process of physically draining the stomach’s contents using a nasogastric tube, to remove gastric secretions and swallowed air. It can be used in preparation for surgery and to extract gastric liquid for research purposes.

Assessing effectiveness

As aspiration pneumonitis is a rare event, it is difficult to conduct a randomised controlled trial large enough to demonstrate the effectiveness of an intervention to reduce risk. For this reason, clinical trials on prophylactic drugs have focused on the surrogate measures of gastric pH and volume. This is a disadvantage because there is no guarantee that a change in the surrogate measure will reflect a difference in outcome of interest (i.e. aspiration pneumonitis). The pathophysiology of aspiration pneumonitis relates to both the volume and the acidity of the fluid aspirated. An intragastric pH lower than 2.5 and a volume greater than 0.4 ml/kg are the traditionally described criteria for increased risk of severe lung injury and mortality. These criteria were originally described by Mendelson (Mendelson 1946), and were derived from animal experiments (Roberts 1974). However, the evidence that these surrogate measures increase the risk of aspiration pneumonitis in pregnant women undergoing caesarean section under general anaesthesia is absent. Failure to adequately raise intragastric pH and lower intragastric volume may not be due to the specific drug, but due to other factors, such as the time interval between administration and surgery, or to interaction with other drugs. Opioids in particular slow down gastric emptying and can reduce the effectiveness of prophylactic drugs used. Measurements are usually taken just after induction of anaesthesia and just before extubation (removal of the endotracheal tube) to reflect the intragastric conditions at the time of greatest aspiration risk (Ewart 1990; Gin 1990; Moore 1989; Tripathi 1995).

Why it is important to do this review

The administration of an antacid and H₂ receptor antagonist, and sometimes a prokinetic and antiemetic drug (such as metoclopramide, a phenothiazine-like drug aimed at accelerating gastric emptying and reducing nausea, vomiting and aspiration pneumonitis), has been standard practice prior to caesarean section in maternity units in the United Kingdom (Thomas 2001). However, clinical practice has varied across the world. Some countries including the UK also routinely administer drugs (such as ranitidine) to all women in labour with the aim of reducing the risk of aspiration pneumonitis should anaesthesia be required for caesarean section, even though the evidence for such practice is poor (Gyte 2006). Any pharmacological intervention may produce side effects or serious complications, including anaphylaxis. Pharmacological antiemetics are associated with a number of side effects such as excessive sedation, restlessness, dystonic reactions (abnormal muscle tone) and extra pyramidal symptoms (Numazaki 2000).

There is a need to review the evidence of effectiveness of pharmacological drugs to reduce aspiration pneumonitis for women who have caesarean sections. The evidence of effectiveness of pharmacological and non-pharmacological interventions to prevent nausea and vomiting for women who have caesarean sections will be considered in a separate review on ’Interventions for reducing nausea and vomiting at caesarean section’.

OBJECTIVES

To determine whether interventions given prior to caesarean section reduce the risk of aspiration pneumonitis in women with an uncomplicated pregnancy (i.e. women who had no medical complications other than the obstetric reason for caesarean section).

METHODS

Criteria for considering studies for this review

Types of studies

All published or unpublished randomised controlled trials (RCTs), including cluster-randomised trials. We excluded quasi-RCTs.

Types of participants

Pregnant women undergoing elective or emergency caesarean section under general or regional anaesthesia.

Types of interventions

Any pharmacological or non-pharmacological intervention given specifically to prevent aspiration pneumonitis at caesarean section.

1. Particulate or non-particulate antacids

2. H₂ antagonists (e.g. ranitidine)

3. Proton pump antagonists (e.g. omeprazole)

4. Prokinetic drugs (e.g. metoclopramide)

5. Non-pharmacological interventions

Comparisons were any of the above interventions versus any other, placebo or no intervention.

Types of outcome measures

Primary outcomes

1. Incidence of mortality due to aspiration pneumonitis

2. Incidence of morbidity due to aspiration pneumonitis

3. Low intragastric pH below 2.5, measured after induction of anaesthesia

4. Increase of intragastric volume to more than 0.4 ml/kg, measured after induction of anaesthesia

Secondary outcomes

1. Women’s satisfaction

2. Incidence of nausea during caesarean section or the postoperative period

3. Incidence of vomiting during caesarean section or the postoperative period

4. Side effects - including sedation, restlessness, dystonic reactions and extrapyramidal symptoms.

5. Adverse event - episodes of hypotension, blood loss, atonic uterus

6. Neonatal morbidity - cord blood pH, Apgar scores, neonatal assessment scores and admission to neonatal intensive care unit

7. Breastfeeding rates - initiation of breastfeeding and duration of breastfeeding

8. Raised intragastric pH above 2.5, measured prior to extubation at the end of anaesthesia

9. Reducing of intragastric volume to less than 0.4 ml/kg, measured prior to extubation at the end of anaesthesia

In order to try to avoid outcome reporting bias in the review, studies will be included whether or not they have assessed these specific outcomes listed here. Where included studies have not reported any of our pre-specified outcomes, we have included them in the review and information can be found in the ’Characteristics of included studies’.

Many trials measured ’at risk of aspiration’ as the number of individuals who had both low gastric pH (less than 2.5) and increased gastric volume (greater than 0.4ml/kg). Although this combined measure was not one of our pre-specified outcomes we have included it in this review.

We looked for individual components of ’side effects’ and ’adverse events’. To date there are limited data for these outcomes. If more data become available in the future, we will analyse these as composite outcomes.

Search methods for identification of studies

Electronic searches

We searched the Cochrane Pregnancy and Childbirth Group’s Trials Register by contacting the Trials Search Co-ordinator (April 2009).

The Cochrane Pregnancy and Childbirth Group’s Trials Register is maintained by the Trials Search Co-ordinator and contains trials identified from:

1. quarterly searches of the Cochrane Central Register of Controlled Trials (CENTRAL);

2. weekly searches of MEDLINE;

3. handsearches of 30 journals and the proceedings of major conferences;

4. weekly current awareness alerts for a further 44 journals plus monthly BioMed Central email alerts.

Details of the search strategies for CENTRAL and MEDLINE, the list of handsearched journals and conference proceedings, and the list of journals reviewed via the current awareness service can be found in the ’Specialized Register’ section within the editorial information about the Cochrane Pregnancy and Childbirth Group.

Trials identified through the searching activities described above were each assigned to a review topic (or topics). The Trials Search Co-ordinator searches the register for each review using the topic list rather than keywords.

We did not apply any language restrictions.

Data collection and analysis

Selection of studies

We obtained the full text of all potentially relevant studies and all review authors independently applied the inclusion criteria. Four authors (S Paranjothy, H Broughton, J Griffiths and G Gyte) assessed the trials for eligibility and methodological quality without consideration of the results.

Data extraction and management

We designed a data extraction form. Review authors (S Paranjothy, J Griffiths, H Broughton and G Gyte) independently extracted data, two for each included study using the forms, and then compared the results for discrepancies and process as described in Higgins 2008. Reasons for excluding any trial were given.

Trials were not assessed blindly, as we knew the author’s name, institution and the source of publication. We resolved any disagreement by discussion until a consensus was reached. We contacted authors for each included trial for further information, as necessary.

We performed statistical analysis using the Review Manager software (RevMan 2008).

Assessment of risk of bias in included studies

Two review authors independently assessed risk of bias for each study using the criteria outlined in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2008). We resolved any disagreement by discussion.

(1) Sequence generation (checking for possible selection bias)

We described for each included study the methods used to generate the allocation sequence in sufficient detail to allow an assessment of whether it should produce comparable groups.

We assessed the methods as:

• adequate (e.g. random number table; computer random number generator);

• inadequate (e.g. odd or even date of birth; hospital or clinic record number); or

• unclear.

2) Allocation concealment (checking for possible selection bias)

We described for each included study the method used to conceal the allocation sequence in sufficient detail and determine whether intervention allocation could have been foreseen in advance of, or during recruitment, or changed after assignment.

We assessed the methods as:

• adequate (e.g. telephone or central randomisation; consecutively numbered sealed opaque envelopes);

• inadequate (e.g. open random allocation; unsealed or non-opaque envelopes, alternation; date of birth);

• unclear.

(3) Blinding (checking for possible performance bias)

We described for each included study all the methods used, if any, to blind study participants and personnel from knowledge of which intervention a participant received. We also provided any information relating to whether the intended blinding was effective. We noted where there was partial blinding (e.g. where it has not been possible to blind participants but where outcome assessment was carried out without knowledge of group assignment). Where blinding was not possible, we assessed whether the lack of blinding was likely to have introduced bias.

We assessed the methods as:

• adequate, inadequate or unclear for participants;

• adequate, inadequate or unclear for personnel;

• adequate inadequate or unclear for outcome assessors.

where ’adequate’ was when there was blinding or where we assessed that the outcome or the outcome measurement is not likely to have been influenced by lack of blinding.

4) Incomplete outcome data (checking for possible attrition bias through withdrawals, dropouts, protocol deviations)

We described for each included study the completeness of outcome data for each main outcome, including attrition and exclusions from the analysis. We stated whether attrition and exclusions were reported, the numbers included in the analysis at each stage (compared with the total randomised participants), reasons for attrition or exclusion where reported, and any re-inclusions in analyses which we undertook.

We assessed the methods as:

• adequate (e.g. where there were no missing data or where reasons for missing data were balanced across groups);

• inadequate (e.g. where missing data are likely to be related to outcomes or are not balanced across groups, or where high levels of missing data are likely to introduce serious bias or make the interpretation of results difficult;

• unclear (e.g. where there is insufficient reporting of attrition or exclusions to permit a judgement to me made).

5) Selective reporting bias

We described for each included study how the possibility of selective outcome reporting bias was examined by us and what we found.

We assessed the methods as:

• adequate (where it is clear that all of the study’s prespecified outcomes and all expected outcomes of interest to the review have been reported);

• inadequate (where not all the study’s prespecified outcomes have been reported; one or more reported primary outcomes were not prespecified; outcomes of interest are reported incompletely and so cannot be used; study fails to include results of a key outcome that would have been expected to have been reported);

• unclear.

6) Other sources of bias

We described for each included study any important concerns we have about other possible sources of bias. For example, was there a potential source of bias related to the specific study design? Was the trial stopped early due to some data-dependent process? Was there extreme baseline imbalance? Has the study been claimed to be fraudulent?

We assessed whether each study was free of other problems that could put it at risk of bias:

• yes;

• no;

• unclear.

7) Overall risk of bias

We made explicit judgements about risk of bias for important outcomes both within and across studies. With reference to (1) to (6) above, we assessed the likely magnitude and direction of the bias and whether we considered it was likely to impact on the findings. We intended to explore the impact of the level of bias through undertaking sensitivity analyses (see ’Sensitivity analysis’); however, this was not possible given the limited amount of data. We will explore this in future updates should more data become available for analysis.

Measures of treatment effect

We carried out statistical analysis using the Review Manager software (RevMan 2008). We used fixed-effect meta-analyses for combining data in the absence of significant heterogeneity. Where there was heterogeneity, where results were being pooled from studies examining different interventions, or where it is not clear that the same outcome was being measured in all studies, we used random-effects meta-analyses.

Dichotomous data

For dichotomous data, we presented results as summary risk ratio with 95% confidence intervals.

Continuous data

For continuous data, we used the mean difference if outcomes were measured in the same way between trials. We used the standardised mean difference to combine trials that measure the same outcome, but use different methods.

Unit of analysis issues

Cluster-randomised trials

We did not identify any cluster-randomised trials; however, if these are identified in future updates we will include these in the analyses along with individually-randomised trials, using the methods described in Gates 2009.

Dealing with missing data

For included studies, levels of attrition were noted. The impact of including studies with high levels of missing data in the overall assessment of treatment effect was to be explored by using sensitivity analysis. However, we felt there were insufficient data within any one comparison to undertake sensitivity analyses by levels of missing data.

Intention-to-treat analysis

For all outcomes, analyses were carried out, as far as possible, on an intention-to-treat basis, i.e. we analysed data on all participants with available data in the group to which they are allocated, regardless of whether or not they received the allocated intervention. If in the original reports participants were not analysed in the group to which they were randomised, and there was sufficient information in the trial report, we attempted to restore them to the correct group. We attempted to include all participants randomised to each group in the analyses.

The denominator for each outcome in each trial was the number randomised minus any participants whose outcomes were known to be missing.

Assessment of heterogeneity

We have assessed statistical heterogeneity in each meta-analysis using the T² (tau-squared), I² and Chi² statistics. We have regarded heterogeneity as substantial if T² was greater than zero and either I² was greater than 30% or there was a low p-value (less than 0.10) in the Chi² test for heterogeneity. Where we found heterogeneity and random effects was used, we have reported the average risk risk, or average mean difference or average standard mean difference.

Assessment of reporting biases

Had there been 10 or more studies in a meta-analysis we would have investigated reporting biases (such as publication bias) using funnel plots. We would have assessed funnel plot asymmetry visually, and would have used formal tests for funnel plot asymmetry. For continuous outcomes we would have used the test proposed by Egger 1997, and for dichotomous outcomes we would have used the tests proposed by Harbord 2006. If asymmetry had been detected by any of these tests or been suggested by a visual assessment, we would have performed exploratory analyses to investigate it.

Where we suspected reporting bias (see ’Selective reporting bias’ above), we attempted to contact study authors asking them to provide missing outcome data. Where this was not possible, and the missing data were thought to introduce serious bias, the impact of including such studies in the overall assessment of results was explored by a sensitivity analysis.

Where we suspected publication bias (e.g. where only statistically significant results are reported), this was explored using visual assessment of funnel plots (Higgins 2008).

Data synthesis

We have carried out statistical analysis using the Review Manager software (RevMan 2008). We have used fixed-effect meta-analysis for combining data where it was reasonable to assume that studies were estimating the same underlying treatment effect: i.e. where trials were examining the same intervention, and the trials’ populations and methods were judged sufficiently similar. If there was clinical heterogeneity sufficient to expect that the underlying treatment effects differed between trials, or if substantial statistical heterogeneity was detected, we have used random-effects analysis to produce an overall summary, if this was considered clinically meaningful. If an average treatment effect across trials was not clinically meaningful we have not combined heterogeneous trials. If we used random-effects analyses, the results have been presented as the average treatment effect and its 95% confidence interval, the 95% prediction interval for the underlying treatment effect, and the estimates of T² and I².

We combined results of trials using drugs that have the same mechanism of action if the treatment regimens are assessed to be compatible. For example, studies comparing ranitidine versus placebo and famotidine versus placebo will be combined to assess the effectiveness of the H₂ antagonist class of drugs. We also combined routes of administration, for example, studies comparing intravenous ranitidine and oral ranitidine were combined.

Subgroup analysis and investigation of heterogeneity

We undertook subgroup analyses for all the prespecified primary and secondary outcomes where the data were available. No data-driven post hoc analyses were undertaken. Had there been sufficient data we would have conducted planned subgroup analyses classifying whole trials by interaction tests as described by Deeks 2001.

We had planned to carry out the following subgroup analyses: elective versus emergency caesarean section. However, there were insufficient data to carry out these subgroup analyses.

Sensitivity analysis

We had planned to carry out sensitivity analyses to explore the effect of trial quality for important outcomes in the review. However, as the majority of studies were of poor quality and there were little data for each comparison, this was not feasible. We will, however, consider doing this in future updates, as more data are accumulated from published randomised controlled trials.

RESULTS

Description of studies

See: Characteristics of included studies; Characteristics of excluded studies; Characteristics of studies awaiting classification.

Results of the search

One hundred and thirty-nine studies were identified in the search which covered interventions for reducing nausea, vomiting and aspiration pneumonitis at caesarean section. Of these, 23 studies were identified that related to interventions for reducing aspiration pneumonitis and 66 were assigned to the review on nausea and vomiting (Griffiths 2009).

Included studies

Of the 23 studies that were identified relating to the reduction of aspiration pneumonitis, 22 were included involving 2658 women (Dewan 1985; Elhakim 2005; Ewart 1990; Frank 1984;Hong 2004; Husemeyer 1980; Iqbal 2000; Jasson 1989; Lin 1996; Ormezzano 1990; Orr 1993; Ostheimer 1982; Ozkan 2000;Pickering 1980; Rocke 1994; Rout 1993; Tripathi 1995; Tryba 1983; Wig 1987; Yau 1992; Zoroglu 1999; Zue 1999). One study was put in section on ’Awaiting classification’ whilst we try to contact authors (Karamanlioglu 1995).

Excluded studies

The excluded studies are listed in the reference section under excluded studies and the table ’Characteristics of excluded studies’ states the reasons for exclusion from this review. Most of the studies that were excluded assessed interventions for reducing nausea and vomiting at caesarean section rather than reducing the risk of aspiration pneumonitis, though the search strategy included both these circumstances in line with the original protocol. The studies looking at nausea and vomiting are included in the review of interventions for reducing nausea and vomiting at caesarean section (Griffiths 2009).

Risk of bias in included studies

Overall, the quality of studies was difficult to assess. We did not assess any trial protocols so we were unable to assess possible selective reporting bias. In addition, most trials reported only a few outcomes; therefore it is unclear whether or not there is selective reporting bias. Only one study had both adequate sequence generation and concealment allocation (Rout 1993), and the remainder were unclear with two studies having inadequate allocation concealment (Dewan 1985; Jasson 1989). The assessment of incomplete data showed half the studies having low risk of bias here and in the other half it was unclear. Only one study met the criteria of low risk of bias on all the assessment criteria (Rout 1993) (Figure 1).

Figure 1 . Methodological quality summary: review authors’ judgements about each methodological quality item for each included study.

Allocation

The random sequence generation was adequate in only two studies (Elhakim 2005; Rout 1993), with the remainder of the studies being unclear. Concealment allocation was adequate in only two studies (Rocke 1994; Rout 1993); in two studies it was inadequate (Dewan 1985; Jasson 1989); and in the rest it was unclear. Thus, there was only one study (Rout 1993) where both generation and concealment were adequate.

Blinding

Blinding was assessed as adequate in six studies (Elhakim 2005; Iqbal 2000; Lin 1996; Rocke 1994; Rout 1993; Tripathi 1995), inadequate in nine (Dewan 1985; Frank 1984; Husemeyer 1980;Jasson 1989; Ormezzano 1990; Ostheimer 1982; Pickering 1980; Wig 1987; Zue 1999) and unclear in the rest of the studies. This is disappointing for studies assessing drug administration.

Incomplete outcome data

Eleven studies were assessed as having adequate reporting of outcome data (Dewan 1985; Elhakim 2005; Husemeyer 1980; Iqbal 2000; Ormezzano 1990; Pickering 1980; Rocke 1994; Rout 1993;Tripathi 1995; Tryba 1983; Zue 1999) with the remainder being assessed as unclear.

Selective reporting

We did not assess the trial protocol so it is unclear if there is any selective reporting bias. Although we did not specifically identify any selective reporting bias, we were unable to exclude the possibility.

Other potential sources of bias

All the studies appeared free from other biases with the exception of four studies where it was assessed as unclear (Ewart 1990; Hong 2004; Tryba 1983; Zoroglu 1999).

Effects of interventions

This review includes 22 studies and 16 meta-analyses, involving 2658 women.

(1) Antacids versus placebo/no treatment (three studies, 168 women)

Three studies compared antacids with placebo (Dewan 1985;Ormezzano 1990, Wig 1987).

The studies were of doubtful quality with sequence generation being unclear in all three studies, and allocation concealment being either unclear in two (Ormezzano 1990; Wig 1987) or inadequate in one (Dewan 1985). Data collection appeared complete in two studies (Dewan 1985; Ormezzano 1990) and unclear in one study (Wig 1987). There appeared to be no other sources of bias apparent in any of the studies.

Primary outcomes

Antacid, compared to placebo, was associated with a statistically significant reduction in:

• intragastric pH less than 2.5 at intubation (risk ratio (RR) 0.17, 95% confidence interval (CI) 0.09 to 0.32, two studies, 108 women, Analysis 1.3).

Other primary outcomes were not assessed.

Secondary outcomes

Antacid, compared with placebo, was also associated with a statistically significant reduction in:

• intragastric pH less than 2.5 at extubation (RR 0.21, 95% CI 0.09 to 0.48, one study, 86 women, Analysis 1.21).

Other secondary outcomes were not assessed.

Outcomes not pre-specified

There was no statistically significant difference identified for:

• ’risk of aspiration’ (RR 0.07, 95% CI 0.00 to 1.04, one study, 22 women, Analysis 1.25).

For other non-prespecified outcomes, see Analyses 1.23 to 1.27.

(2) H₂ antagonists versus placebo/no treatment (six studies, 385 women)

Six studies compared H₂ antagonists with placebo/no treatment (Iqbal 2000; Lin 1996; Ozkan 2000; Tryba 1983; Zoroglu 1999;Zue 1999).

The studies were of doubtful quality with unclear sequence generation and concealment allocation in the six studies. Blinding was adequate in two studies (Iqbal 2000; Lin 1996), inadequate in one study (Zue 1999) and unclear in the remainder. Data collection appeared complete in three studies (Iqbal 2000; Tryba 1983; Zue 1999) and unclear in the remainder of studies. The studies seemed to be free of other sources of bias, although this was difficult to assess due to lack of information in some.

Primary outcomes

In women undergoing elective caesarean section, H₂ antagonists compared to placebo showed a statistically significant reduction in:

• intragastric pH less than 2.5 at intubation (RR 0.09, 95% CI 0.05 to 0.18, two studies, 170 women, Analysis 2.3);

• intragastric volume greater than 0.4 mg/kg at intubation (average RR 0.08, 95% CI 0.01 to 0.86, two studies, 170 women, random effects [T² = 1.96, Chi² p = 0.10, I² = 63%], Analysis 2.4).

Other primary outcomes were not assessed.

Secondary outcomes

One study reported on intragastric pH at extubation and found a statistically significant reduction in:

• risk of pH less than 2.5 (RR 0.08, 95% CI 0.01 to 0.56, one study, 30 women, Analysis 2.21).

Other secondary outcomes were not assessed.

Outcomes not pre-specified

H₂ antagonists were associated with a statistically significant reduction in:

• ’Risk of aspiration’ at intubation (average RR 0.07, 95% CI 0.01 to 0.33, 4 studies, 255 women, random effects [T² = 1.35, Chi² p = 0.11, I² = 51%], Analysis 2.25)

• Risk of aspiration’ at extubation (RR 0.17, 95% CI 0.01 to 4.03, 2 studies, 125 women [although only one study of 75 women was estimable], Analysis 2.26).

For other non-prespecified outcomes see Analyses 2.23 to 2.28.

(3) Proton pump antagonists versus placebo/no treatment (2 studies, 130 women)

Two studies (Lin 1996; Ozkan 2000) compared proton pump antagonists with placebo or no treatment. Both of these studies were of doubtful quality as allocation sequence generation, allocation concealment, blinding and incomplete data assessment were unclear. The study by Lin et al reported that the trial was conducted in a “double blind manner” but it was unclear who was blinded or how this was done (Lin 1996). Both studies were judged to be free of other biases although there was limited information on which to judge this.

Primary outcomes

Proton pump antagonists, when compared with placebo, were associated with a statistically significant reduction in:

• intragastric pH less than 2.5 at intubation (RR 0.26 95% CI 0.14, 0.46, one study, 80 women, Analysis 3.3);

• Intragastric volume greater than 0.4 ml/kg (RR 0.46, 95% CI 0.19, 1.09, one study, 80 women, Analysis 3.4).

Other primary outcomes were not assessed.

Secondary outcomes

Neither of these studies reported on our pre-specified secondary outcomes.

Outcomes not pre-specified

Proton pump antagonists were associated with a significant reduction in:

• ’risk of aspiration’ compared with placebo (average RR 0.14, 95% CI 0.03 to 0.74, two studies, 130 women, random effects [T² = 0.60, Chi² p = 0.22, I² = 34%], Analysis 3.24).

For other non-prespecified outcomes, see Analyses 3.23 to 3.27.

(4) Prokinetic drugs versus placebo/no treatment (one study, 50 women)

One study compared a prokinetic drug (metoclopramide) to no treatment (Ozkan 2000). The quality of this study was doubtful as allocation sequence generation, allocation concealment, blinding and incomplete data assessment were unclear. The study was judged to be free of other biases although there was limited information on which to judge this.

Primary outcomes

This study did not measure any of the primary outcomes that were pre-specified in this review.

Secondary outcomes

This study did not measure any of the secondary outcomes that were pre-specified in this review.

Outcomes not pre-specified

When prokinetic drugs were compared with no treatment, there was no statistically significant difference identified in:

• ’risk of aspiration’ (RR 0.67, 95% CI 0.33 to 1.35, one study, 50 women, Analysis 4.23). Though it is possible the study was too small to identify a difference.

(5) Non-pharmacological interventions versus placebo/no treatment (one study, 40 women)

One study compared the use of intravenous 5% dextrose solution to Normal Saline solution prior to induction of anaesthesia in 40 women undergoing elective caesarean section in South Korea (Hong 2004). This study was of doubtful quality as there was no information given to assess adequacy of sequence generation, allocation concealment, blinding, incomplete outcome data assessment. It was not clear if the study was free of any other bias, due to the lack of detail available.

Primary outcomes

This study did not report on any of the primary outcomes prespecified in this review.

Secondary outcomes

This study did not report on any of the secondary outcomes pre-specified in this review.

Outcomes not pre-specified

There was no statistically significant difference identified in:

• ’risk of aspiration’ (not clearly defined) (RR 0.50, 95% CI 0.18 to 1.40, one study, 40 women, Analysis 5.23).

(6) Antacids + H₂ antagonists versus placebo/no treatment (one study, 89 women)

One study compared the use of antacids and H₂ antagonists (in combination) with no treatment (Ormezzano 1990). This study was of doubtful quality as sequence generation and allocation concealment were unclear. Neither the participants nor the outcome assessors were blinded. However, data completeness were adequately assessed and this study was judged to be free of selective reporting bias or any other type of bias.

Primary outcomes

The combination of an ’antacid plus an H₂ receptor antagonist’ compared with placebo showed:

• a statistically significant reduction in risk of gastric pH less than 2.5 at intubation (RR 0.02, 95% CI 0.00 to 0.15, one study, 89 women, Analysis 6.3).

Other primary outcomes were not assessed.

Secondary outcomes

The combination also showed a statistically significant reduction in:

• risk of gastric pH less than 2.5 at extubation (RR 0.03, 95% CI 0.00 to 0.24, one study, 89 women, Analysis 6.21).

Other secondary outcomes were not assessed.

Outcomes not pre-specified

For non-prespecified outcomes, see Analyses 6.23 to 6.24.

(7) H₂ antagonists + prokinetic drugs versus placebo/no treatment (one study, 50 women)

One study compared the use of H₂ antagonists plus prokinetic drugs (in combination) with no treatment (Iqbal 2000). This study was of doubtful quality as sequence generation and allocation concealment were unclear. Participants and clinicians were reported to be blinded. There was no description of data completeness and it was unclear if the study was free from selective reporting bias or any other types of bias.

Primary outcomes

The combination of ’H₂ antagonists plus prokinetic drugs’ were associated with:

• a statistically significant reduction gastric pH less than 2.5 after induction (RR 0.03, 95% CI 0.00, 0.48, one study, 50 women, Analysis 7.3).

Secondary outcomes

This study did not report on any of the secondary outcomes pre-specified in this review.

Outcomes not pre-specified

The was a statistically significant reduction in women:

• at ’risk of aspiration’ (RR 0.03, 95% CI 0.00, 0.51, one study, 50 women, Analysis 7.23).

For non-prespecified outcomes, see Analyses 7.24 to 7.26.

(8) Antacids versus H₂ antagonists (four studies, 175 women)

Four studies (Frank 1984; Husemeyer 1980; Ostheimer 1982;Pickering 1980) compared antacids versus H₂ antagonists.

All of these studies were of doubtful quality as allocation sequence generation and allocation concealment were unclear and blinding was not done. Two studies (Husemeyer 1980; Pickering 1980) were judged to have adequate incomplete data assessment; while there was not enough information to assess this in the other two studies (Frank 1984; Ostheimer 1982). All four studies were considered to be free of selective reporting or other bias.

Primary outcomes

Compared with H2 receptor antagonists, antacid use was associated with:

• a statistically significant reduction in risk of pH less than 2.5 at intubation (RR 0.07, 95% CI 0.01 to 0.52, two studies, 135 women, Analysis 8.3).

One study (Frank 1984) also examined the effect of this comparison in women undergoing emergency caesarean section but did not observe any events (pH less than 2.5 at intubation) in either group. Other primary outcomes were not assessed.

Secondary outcomes

None of the prespecified secondary outcomes in this review were reported in these studies.

Outcomes not pre-specified

There was no significant difference identified in:

• ’risk of aspiration’ between the two groups (RR 1.00, 95% CI 0.18, 5.46, one study, 16 women, Analysis 8.23). At risk of aspiration was defined as pH less than 2.5 and gastric volume of at least 25 ml.

For other non-prespecified outcomes, see Analyses 8.24 to 8.26. In contrast to the above finding, these data showed a benefit for H₂ receptor antagonists, for the outcome of gastric volume measured as a continuous variable, as expected due to the nature of the treatments. However, one small study (24 women) evaluated gastric pH as a continuous variable and showed a benefit for H₂ receptor antagonists (Ostheimer 1982).

(9) Antacids versus prokinetic drugs (no studies)

There were no studies that assessed this comparison.

(10) H₂ antagonists versus proton pump antagonists (four studies, 332 women)

Four studies (Ewart 1990; Lin 1996; Tripathi 1995; Yau 1992) compared H₂ antagonists with proton pump antagonists.

All of these studies were of doubtful quality as allocation sequence generation and allocation concealment were unclear. Blinding was done only in two studies (Lin 1996; Tripathi 1995). Only one study (Tripathi 1995) was judged to have adequate incomplete data assessment. All four studies were considered to be free of selective reporting bias or other bias, except for Ewart 1990 where there was not enough information to assess this.

Primary outcomes

Compared with proton pump inhibitors, H₂ receptor antagonists showed a statistically significant reduction in:

• risk of pH less than 2.5 for women undergoing elective caesarean (RR 0.39, 95% CI 0.16 to 0.97, one study, 120 women, Analysis 10.3).

Secondary outcomes

None of these studies reported on the secondary outcomes that were pre-specified in this review

Outcomes not pre-specified

All four studies (Ewart 1990; Lin 1996; Tripathi 1995; Yau 1992) on women undergoing elective and emergency caesarean section reported on ’at risk of aspiration’.

• There was no statistically significant difference in risk identified (average RR 0.93, 95% CI 0.20 to 4.37, four studies, 323 women, random effects [T² = 0.80, Chi² p = 0.22, I² = 32%], Analysis 10.23).

For other non-prespecified outcomes, see Analyses 10.24 to 10.27.

(11) Antacids + H₂ antagonists versus antacids (two studies, 714 women)

Two studies compared the combined use of antacids and H₂ antagonists versus antacids (Ormezzano 1990; Rout 1993). One study (Rout 1993) was judged to be of good quality with an adequate score on each of the domains that were used to assess risk of bias. In the other study (Ormezzano 1990), sequence generation and allocation were unclear and there was no blinding. However, incomplete outcome data were addressed and the study was judged to be free of selective reporting or other bias.

Primary outcomes

In women undergoing both emergency and elective caesarean section, a combination of antacid plus H₂ receptor antagonists compared with antacids alone showed:

• a significant reduction in risk of pH less than 2.5 at intubation (RR 0.12, 95% CI 0.02 to 0.92, one study, 119 women, Analysis 11.3).

Other primary outcomes were not assessed.

Secondary outcomes

None of the secondary outcomes pre-specified in this review were reported by these studies.

Outcomes not pre-specified

There was a significant reduction in risk of acid aspiration for women undergoing emergency caesarean section with a combination of antacid plus H₂ receptor antagonists compared with antacids alone

• (RR 0.10, 95 % CI 0.02 to 0.45, one study, 595 women, Analysis 11.27).

For other non-prespecified outcomes, see Analyses 11.23 to 11.26.

(12) H₂ antagonists + prokinetic drugs versus antacids (no studies)

There were no studies that assessed this comparison.

(13) Proton pump agonists + prokinetics versus proton pump agonists (no studies)

There were no studies that assessed this comparison.

(14) H₂ antagonist versus Tramadol (one study, 60 women)

One study compared H₂ receptor antagonists with Tramadol (both by intramuscular injection) in 60 women undergoing elective caesarean section (Elhakim 2005). Although most aspects of the assessment of risk of bias were assessed as low risk, allocation concealment was uncertain and this gives an overall uncertain level of risk of bias for the study.

Primary outcomes

Compared with tramadol, H₂ antagonists showed a statistically significant increase in:

• risk of intragastric volume greater than 0.4mg/kg at intubation (RR 5.00, 95% CI 1.03 to 24.28, one study, 90 women, Analysis 14.4).

Other primary outcomes were not assessed.

Secondary outcomes

There was no statistically significant difference identified in:

• nausea (RR 1.38, 95% CI 0.64 to 2.93, one study, 60 women, Analysis 14.5). Other secondary outcomes were not assessed.

Outcomes not pre-specified

This study also included ’at risk of aspiration’ defined as gastric volume greater than 0.4 ml/kg and pH less than 2.5, but there were no events observed in either group for this outcome.

(15) Antacids + H₂ antagonists versus proton pump antagonists (one study, 109 women)

One study compared antacids plus H₂ receptor antagonists with proton pump antagonists in women undergoing emergency caesarean section (Yau 1992). The study was of unclear quality with insufficient information to assess the main aspects of risk of bias.

Primary outcomes

This study did not measure any of the primary outcomes that were pre-specified in this review.

Secondary outcomes

This study did not measure any of the secondary outcomes that were pre-specified in this review.

Outcomes not pre-specified

Compared with proton pump antagonists, H₂ receptor antagonists showed a statistically significant reduction in:

• ’risk of gastric aspiration’ (RR 0.12, 95% CI 0.02 to 0.91, one study, 108 women, Analysis 15.23).

(16) Proton pump antagonist + antacid versus proton pump antagonist (one study, 113 women)

One study assessed proton pump antagonists plus antacids with proton pump antagonist alone in women undergoing emergency caesarean section (Yau 1992). The study was of unclear quality with insufficient information to assess the main aspects of risk of bias.

Primary outcomes

This study did not measure any of the primary outcomes that were pre-specified in this review.

Secondary outcomes

This study did not measure any of the secondary outcomes that were pre-specified in this review.

Outcomes not pre-specified

There was no statistically significant difference identified in:

• risk of gastric aspiration between the two interventions (RR 0.33. 95% CI 0.10 to 1.15, one study, 113 women, graph 16.23).

(17) H₂ antagonist + prokinetic versus H₂ antagonist (one study, 50 women)

One study assessed a combination of H₂ receptor antagonists plus prokinetic versus H₂ receptor antagonists alone in women undergoing elective caesarean section (Iqbal 2000). The study was unclear regarding the randomisation sequence generation and allocation concealment and was thus of unclear quality.

Primary outcomes

This study did not measure any of the primary outcomes that were pre-specified in this review.

Secondary outcomes

This study did not measure any of the secondary outcomes that were pre-specified in this review.

Outcomes not pre-specified

There was no significant difference in risk of gastric aspiration between the two interventions (Analysis 17.23).

For non prespecified outcomes, see Analyses 17.24, 17.26 and 17.27.

DISCUSSION

Summary of main results

Although the studies were generally of poor quality, the findings from this review have shown that:

1. compared to no treatment or placebo, antacids, H₂ antagonists and proton pump antagonists each reduce the risk of intragastric pH less than 2.5 at intubation. The studies on prokinetic drugs and non-pharmacological interventions did not assess this outcome and, in addition, were probably too small to be able identify any differences;

2. when antacids were compared with H₂ antagonists, the findings were unclear as to which drug might be more effective for increasing gastric pH, although antacid use was associated with increase in gastric volume;

3. H₂ antagonists were associated with a reduced risk of intragastric pH less than 2.5 at intubation when compared with proton pump antagonists;

4. the combination of ’antacids plus H₂ antagonists’ or ’prokinetic drugs plus H₂ antagonists’ also reduced the risk of intragastric pH less than 2.5 at intubation, when compared to placebo or no treatment;

5. when compared to antacid use only, the combination of ’antacids plus H₂ antagonists’ was associated with a reduction in the risk of intragastric pH less than 2.5 at intubation.

Overall completeness and applicability of evidence

Aspiration pneumonitis is a rare outcome and therefore the primary outcome measure in the studies that we identified were surrogate measures, i.e. intragastric pH and intragastric volume. The validity of these surrogate markers, however, is uncertain as it is based on work on animal experiments from 1974 (Roberts 1974). Many studies have defined and reported high risk of aspiration as a combination of low intragastric pH (less than 2.5) and raised intragastric volume (greater than 25 ml). This combined measure was not a pre-specified outcome in our review but we have included and presented the data on this for completeness. The studies did not answer the broader question of whether the surrogate markers (of pH and gastric volume) actually correlate with clinical outcome in the context of aspiration pneumonitis.

All but two of the studies that we identified in this review included women who had caesarean section (CS) under general anaesthesia. One study (Lin 1996) studied women who had CS under spinal anaesthesia and the type of anaesthesia used was unclear in one study (Zue 1999). The majority of studies included women who had elective CS (N = 16), five studies included women who had emergency CS, hence we are unable to draw conclusions about the differences between elective and non-elective CS. The findings of this review are generally applicable for women having CS under general anaesthesia (or those who convert from regional to general anaesthesia). Aspiration under regional anaesthesia is exceptionally rare, but may occur in the presence of other serious clinical problems such as seizures and life threatening haemorrhage.

Quality of the evidence

The quality of studies included in this review was generally poor. Only one study was assessed to have adequate sequence generation (Rout 1993), but this study did not report on any of the pre- specified outcomes of this review. It was unclear whether or not randomisation sequence generation and allocation concealment were adequate in the majority of studies. The majority of studies were not blinded, although this could have been feasibly done.

Potential biases in the review process

The possibility of introducing bias was present at every stage of reviewing process. We attempted to minimise bias in a number of ways; two review authors assessed eligibility for inclusion, carried out data extraction and assessed risk of bias. Each worked independently. Nevertheless, the process of assessing risk of bias, for example, is not an exact science and includes many personal judgements.

Agreements and disagreements with other studies or reviews

Current practice in the UK mostly includes the administration of the combination of antacids and H₂ antagonists prior to CS (Thomas 2001). However, this is not routine practice in many centres worldwide. The findings from this review suggest that the combined use of antacids and H₂ antagonists have a role in reducing intragastric pH less than 2.5, and hence possibly in reducing the risk of aspiration pneumonitis during CS, particularly under general anaesthesia.

AUTHORS’ CONCLUSIONS

Implications for practice

In summary, the quality of the evidence was poor, but the findings suggest that the combination of antacids plus H₂ antagonists was shown to be more effective than no intervention, and superior to antacids alone in increasing gastric pH. When a single agent is used, antacids alone are superior to H2 antagonists, which are superior to proton pump inhibitors for increasing gastric pH. The effects of treatments on gastric volume are less consistently reported. These findings are relevant for all women undergoing caesarean section, particularly those under general anaesthesia. Whether women undergoing caesarean section under regional anaesthesia should receive aspiration prophylaxis is a clinical judgement; however, since the treatments are relatively well tolerated, and inexpensive, their use should be strongly considered in view of the potential of benefit, particularly as aspiration still is a cause of maternal mortality.

Implications for research

This review confirms the efficacy of many of the commonly used aspiration prophylaxis regimens compared to placebo in reducing gastric pH and volume. However, many studies, particularly those examining combinations of different modalities of prophylaxis, are small and of generally poor quality. Large well-designed studies that include women having emergency and elective caesarean section under regional and general anaesthesia are required to confirm the conclusions of this review.

Further work is required to validate the suitability of surrogate markers (of pH and gastric volume) for clinical outcomes in the context of aspiration pneumonitis.

PLAIN LANGUAGE SUMMARY.

Interventions at caesarean section for reducing the risk of lung damage from inhaling stomach contents during anaesthesia

Stomach contents can regurgitate up the gullet into the wind pipe and enter the lungs when there is no cough reflex, e.g. during general anaesthesia. Solid food can block airways and cause breathing difficulties. The acidic liquid from the stomach can damage the lungs. This is called aspiration pneumonitis or Mendelsohn’s syndrome. It can lead to serious illness or even death. Many caesarean sections now are undertaken using epidural or spinal anaesthesia, and here the risk is much lower because the woman stays awake and the cough reflex remains intact. A breathing tube, which provides a seal, is normally placed in the windpipe when setting up a general anaesthetic to try to prevent this problem. However, aspiration can still occur before the tube is inserted and when it is removed. It is thought that both the acidity and amount of fluid inhaled contribute to how much damage occurs in the lungs in the event of inhalation of the fluid into the lungs and how sick people become.

This review found 22 studies involving 2658 women looking at interventions given prior to caesarean section for reducing the risk of aspiration. There were several different drugs and drug combinations being considered and the studies were generally of poor or questionable quality. Antacids (like sodium citrate), H₂ receptor antagonists (like ranitidine), proton pump antagonists (like omeprazole), all reduced the acidity of the stomach contents. An antacid plus an H₂ receptor antagonist also reduced acidity. In theory, a combination like this, where the antacid acts quickly and the H₂ receptor antagonists takes a little longer, should protect at periods of greatest risk, i.e. the beginning and end of the procedure (i.e. intubation and extubation). More research is needed to identify the best combination of drugs and to check for possible adverse effects.

CHARACTERISTICS OF STUDIES

Characteristics of included studies [ordered by study ID]

Dewan 1985

Methods	Randomised women to 3 groups.
Participants	Healthy women at term scheduled for elective CS under GA. N = 32.
Interventions	30 ml 0.3 M sodium citrate < 60 min pre-op (intervention group1). 30 ml 0.3 M sodium citrate > 60 min pre-op (intervention group 2). No antacid (comparison group).
Outcomes	Gastric volume and pH postintubation.
Notes	We excluded data from the group that was given antacid > 60min pre-op as the optimum effectiveness for giving antacids is within 60 min of the operation
Risk of bias
Item	Authors’ judgement	Description
Adequate sequence generation?	Unclear	“…randomly assigned”.
Allocation concealment?	No	Not described.
Blinding? All outcomes	No	No mention of blinding.
Incomplete outcome data addressed? All outcomes	Yes	No loss to follow up.
Free of selective reporting?	Unclear	We did not assess the trial protocol.
Free of other bias?	Yes	No evidence of other bias.

Elhakim 2005

Methods	RCT.
Participants	Pregnant women ASA 1 undergoing elective CS. N = 60.
Interventions	Tramadol 100 mg 1 hour before induction to anaesthesia (intervention group) Famotidine 20 mg IM 1 hour before induction to anaesthesia (comparison group)
Outcomes	Gastric pH and volume. Apgar scores. Frequency and severity of nausea. Pain scores. Blood gases - umbilical, venous and arterial blood gases
Notes	Some of the data have been presented as median and range and therefore not used
Risk of bias
Item	Authors’ judgement	Description
Adequate sequence generation?	Yes	Computer-generated random number.
Allocation concealment?	Unclear	Not described.
Blinding? All outcomes	Yes	Paediatrician and anaesthetist.
Incomplete outcome data addressed? All outcomes	Yes	No loss of participants.
Free of selective reporting?	Unclear	We did not assess the trial protocol.
Free of other bias?	Yes	No evidence for other bias.

Ewart 1990

Methods	RCT.
Participants	Scheduled CSs under general anaesthesia in healthy uncomplicated pregnancies of at least 36 weeks N = 70.
Interventions	40 mg omeprazole orally at 22.00 hours and 06.00 in the morning of surgery (intervention group). 150 mg of ranitidine orally at 22.00 hours and 06.00 in the morning of surgery (comparison group)
Outcomes	Gastric volume and ph measured after in the induction of anaesthesia and on completion of surgery Apgar scores.
Notes
Risk of bias
Item	Authors’ judgement	Description
Adequate sequence generation?	Unclear	Not described.
Allocation concealment?	Unclear	Not described.
Blinding? All outcomes	Unclear	Not described.
Incomplete outcome data addressed? All outcomes	Unclear	70 recruited, 5 withdrawn.
Free of selective reporting?	Unclear	We did not assess the trial protocol.
Free of other bias?	Unclear	Unclear how many women were approached but did not want to take part in the trial - this may contribute to selection bias

Frank 1984

Methods	RCT.
Participants	Pregnant women (ASA 1 & 2) at term having either a emergency or elective CS under general anaesthesia N = 42.
Interventions	Elective CS interventions 15 ml mg trisilicate mixture BPC before transfer to theatre and further 15ml before induction of anaesthesia. 15 ml sodium citrate mixture before transfer to theatre and further 15 ml before induction of anaesthesia. Cimetidine 400 mg po night before the operation and 200 mg IM 90 min before the induction of anaesthesia Emergency CS interventions 15 ml mg trisilicate mixture BPC every 2 hours throughout labour and again before induction of anaesthesia. 15 ml of sodium citrate every 2 hours throughout labour and again before induction of anaesthesia. Loading dose of 400 mg of cimetidine po followed by 200 mg po every 2 hours for a maximum of 7 doses
Outcomes	Gastric pH and gastric volume, neonatal Apgar scores.
Notes
Risk of bias
Item	Authors’ judgement	Description
Adequate sequence generation?	Unclear	Not described.
Allocation concealment?	Unclear	Not described.
Blinding? All outcomes	No	No information - unlikely due to the type of interventions involved
Incomplete outcome data addressed? All outcomes	Unclear	Participant loss and exclusion not described.
Free of selective reporting?	Unclear	We did not assess the trial protocol.
Free of other bias?	Yes	No evidence of other bias.

Hong 2004

Methods	RCT.
Participants	Pregnant women undergoing elective CS. N = 40.
Interventions	5% Dextrose 120 ml/hr (intervention group). 120 ml/hr Nsaline (comparison group).
Outcomes	Gastric volume and ph reported as “at risk of aspiration”.
Notes
Risk of bias
Item	Authors’ judgement	Description
Adequate sequence generation?	Unclear	Not described.
Allocation concealment?	Unclear	Not described.
Blinding? All outcomes	Unclear	No details given.
Incomplete outcome data addressed? All outcomes	Unclear	Insufficient detail to assess.
Free of selective reporting?	Unclear	We did not assess the trial protocol.
Free of other bias?	Unclear	Insufficient detail to assess.

Husemeyer 1980

Methods	RCT.
Participants	Elective caesarean section of 37 weeks or more gestation for non acute obstetric indications N = 62.
Interventions	400 mg cimetidine po + 20 ml water 2-6 hours before anaesthesia (intervention group) Magnesium trisilicate mixture BPC 20 ml within 1 hour before anaesthesia (comparison group)
Outcomes	Maternal gastric pH and volume (postinduction of anaesthesia)
Notes	pH data not used as median and range given. Magnesium trisilicate is a particulate antacid and mostly not to be used nowadays
Risk of bias
Item	Authors’ judgement	Description
Adequate sequence generation?	Unclear	Not described.
Allocation concealment?	Unclear	Not described.
Blinding? All outcomes	No	No details of blinding.
Incomplete outcome data addressed? All outcomes	Yes	All participants accounted for.
Free of selective reporting?	Unclear	We did not assess the trial protocol.
Free of other bias?	Yes	No evidence of other bias.

Iqbal 2000

Methods	RCT.
Participants	ASA 1-2 elective CS. N = 75.
Interventions	Ranitidine (intervention group 1). Ranitidine + metoclopramide (intervention group 2). Saline 4 ml (comparison group).
Outcomes	Gastric volume and pH. Risk of aspiration.
Notes	Unclear what dose of ranitidine was given to women.
Risk of bias
Item	Authors’ judgement	Description
Adequate sequence generation?	Unclear	“…randomised”.
Allocation concealment?	Unclear	Not described.
Blinding? All outcomes	Yes	Double-blind manner.
Incomplete outcome data addressed? All outcomes	Yes	Assume ITT.
Free of selective reporting?	Unclear	We did not assess the trial protocol.
Free of other bias?	Yes	No evidence for other bias.

Jasson 1989

Methods	RCT.
Participants	Women undergoing an elective CS under GA. N = 52.
Interventions	Oral sodium citrate 0.3 30 ml 5 min prior to anaesthesia (intervention group). No medication prior to anaesthesia (control group).
Outcomes	Gastric pH and gastric volume.
Notes
Risk of bias
Item	Authors’ judgement	Description
Adequate sequence generation?	Unclear	Method of allocation not stated.
Allocation concealment?	Unclear	Method of allocation not stated.
Blinding? All outcomes	No	Not blinded.
Incomplete outcome data addressed? All outcomes	Yes	No outcome data on 1 patient due to pyloric reflux.
Free of selective reporting?	Unclear	We did not assess the trial protocol.
Free of other bias?	Unclear	Difficult to assess as limited information.

Lin 1996

Methods	RCT.
Participants	Pregnant women ASA 1-2, aged 21-43 years old scheduled for elective CS under regional anaesthesia N = 160.
Interventions	Famotidine 40 mg (intervention group 1). Ranitidine 300 mg (intervention group 2). Omeprazole 40 mg (intervention group 3). Placebo (comparison group).
Outcomes	GastricVolume and pH. Percentage of women at risk of aspiration pH < 2.5 and volume > 0.4 ml/kg
Notes
Risk of bias
Item	Authors’ judgement	Description
Adequate sequence generation?	Unclear	Not described.
Allocation concealment?	Unclear	Not described.
Blinding? All outcomes	Yes	“…double blind”.
Incomplete outcome data addressed? All outcomes	Unclear	5 women excluded as time from premed to CS < 3 hours - unclear which groups these women were excluded from
Free of selective reporting?	Unclear	We did not assess the trial protocol.
Free of other bias?	Yes	No evidence of other bias.

Ormezzano 1990

Methods	RCT.
Participants	Pregnant ASA 1 & 2 women undergoing emergency and elective CS under general anaesthesia N = 147.
Interventions	Nothing (no pre med) (comparison group). 0.3 M sodium citrate 15 ml (intervention group 1). 400 mg cimetidine and 0.9 g sodium citrate in 15 ml water (intervention group 2)
Outcomes	Gastric pH.
Notes
Risk of bias
Item	Authors’ judgement	Description
Adequate sequence generation?	Unclear	Not described.
Allocation concealment?	Unclear	Not described.
Blinding? All outcomes	No	No details of blinding.
Incomplete outcome data addressed? All outcomes	Yes	All women accounted for.
Free of selective reporting?	Unclear	We did not assess the trial protocol.
Free of other bias?	Yes	No evidence of other bias.

Orr 1993

Methods	RCT.
Participants	Healthy pregnant women with an uncomplicated pregnancy of at least 36 weeks to be delivered by elective CS under general anaesthesia N = 94.
Interventions	40 mg omeprazole (po) night before surgery and morning of surgery. 80 mg omeprazole (po) morning of surgery. 40 mg omeprazole (po) night before surgery and morning of surgery, and 10 mg metoclopramide (IM) 20 min before induction of anaesthesia 80 mg omeprazole (po) morning of surgery and 10 mg metoclopramide (IM) 20 min before induction of anaesthesia
Outcomes	Postintubation and pre-extubation gastric pH and volume, Apgar scores, neuro behavioural and adaptive scoring system (NACS), plasma and amniotic fluid omeprazole levels and risk of aspiration (pH < 2.5 and gastric volume ≥ 25 ml)
Notes
Risk of bias
Item	Authors’ judgement	Description
Adequate sequence generation?	Yes	Computer-generated schedule.
Allocation concealment?	Yes	Pre-packed packs with matching placebo capsules and injections
Blinding? All outcomes	Yes	Women, clinicians and outcome assessors were blinded.
Incomplete outcome data addressed? All outcomes	Yes	No postrandomisation exclusions; analysis was by intention to treat
Free of selective reporting?	Unclear	We did not assess the trial protocol.
Free of other bias?	Yes	No evidence of other bias.

Ostheimer 1982

Methods	RCT.
Participants	Pregnant women undergoing elective CS under general anaesthesia N = 24.
Interventions	300 mg cimetidine IM 1 hour prior to induction of general anaesthesia (intervention group) 30 ml antacid (mylanta 2) (comparison group).
Outcomes	Gastric volume and pH. Intrapartum and postpartum complications. Apgar scores 1 and 5 min after birth. Neonatal gastric volumes and pH within 10 min of birth. Brazelton neonatal assessment scale
Notes
Risk of bias
Item	Authors’ judgement	Description
Adequate sequence generation?	Unclear	Not described.
Allocation concealment?	Unclear	Not described.
Blinding? All outcomes	No	No details of blinding.
Incomplete outcome data addressed? All outcomes	Unclear	Not enough data to assess.
Free of selective reporting?	Unclear	We did not assess the trial protocol.
Free of other bias?	Yes	No evidence of other bias.

Ozkan 2000

Methods	RCT.
Participants	Women with singleton pregnancies undergoing elective CS under general anaesthesia N = 150.
Interventions	Oral sodium nitrate (30 ml 0.3 mol/l). Water (200 cc). Ranitidine (50 mg IV). Omeprazole (40 mg IV). Metoclopramide (10 mg IV).
Outcomes	At risk of aspiration defined as gastric residual volume > 0.4 ml and gastric pH < 2.5, postintubation and pre-extubation
Notes	Also included continuous outcomes of gastric pH and gastric residual volume but unclear if data presented are standard deviations or standard errors. We will write to the authors to clarify. In the mean time we have not entered continuous data
Risk of bias
Item	Authors’ judgement	Description
Adequate sequence generation?	Unclear	Not described.
Allocation concealment?	Unclear	Not described.
Blinding? All outcomes	Unclear	Not described.
Incomplete outcome data addressed? All outcomes	Unclear	Not enough data to assess.
Free of selective reporting?	Unclear	We did not assess the trial protocol.
Free of other bias?	Unclear	Difficult to assess as limited information given.

Pickering 1980

Methods	RCT.
Participants	Healthy pregnant women undergoing elective CS under general anaesthesia N = 17.
Interventions	Cimetidine IM 300 mg (intervention group). Antacid 30 ml gelusil (comparison group).
Outcomes	Gastric pH and volume (intraoperative dilution technique) and ’at risk’ pH < 2.5 and volume > 25 ml
Notes	Also measured intraoperative gastric volume using dilution technique
Risk of bias
Item	Authors’ judgement	Description
Adequate sequence generation?	Unclear	Not described.
Allocation concealment?	Unclear	Not described.
Blinding? All outcomes	No	No blinding reported.
Incomplete outcome data addressed? All outcomes	Yes	All women accounted for.
Free of selective reporting?	Unclear	We did not assess the trial protocol.
Free of other bias?	Yes	No evidence for other bias.

Rocke 1994

Methods	RCT.
Participants	Term singleton pregnancies requiring emergency CS under general anaesthesia N = 541.
Interventions	IV omeprazole 40 mg over 1 min at time of decision for CS under GA (intervention group) Placebo (comparison group). NB: Both groups received 10mg IV metoclopramide + 0.3 M sodium citrate 30 ml orally
Outcomes	Volume and pH of stomach contents postintubation and pre extubation. Risk of aspiration
Notes	Apgar score and gastric aspirate data is presented as medians and range and therefore not input
Risk of bias
Item	Authors’ judgement	Description
Adequate sequence generation?	Unclear	Sequence generation not described.
Allocation concealment?	Yes	Pre randomised identical numbered vials.
Blinding? All outcomes	Yes	Women, clinician and outcome assessor.
Incomplete outcome data addressed? All outcomes	Yes	722 recruited and randomised, 181 withdrawn as per exclusion criteria
Free of selective reporting?	Unclear	Data analysed in groups that were assigned but did not measure outcome in 3 controls and 6 in the study group - unable to get enough aspirate. Also we did not assess the trial protocol
Free of other bias?	Yes	No evidence of other bias.

Rout 1993

Methods	RCT
Participants	Women with term singleton pregnancy, emergency CS under general anaesthesia N = 595.
Interventions	50 mg ranitidine IV over 1 min + 30 ml 0.3 M sodium citrate (intervention group). 0.9% sodium chloride IV + 30 ml 0.3 M sodium citrate (comparison group)
Outcomes	Gastric pH and gastric volume - postintubation and pre-extubation. Risk of aspiration
Notes
Risk of bias
Item	Authors’ judgement	Description
Adequate sequence generation?	Unclear	Sequence generation not described.
Allocation concealment?	Yes	Pre randomised identical numbered ampoules.
Blinding? All outcomes	Yes	Double blind, identical preparation pre-prepared.
Incomplete outcome data addressed? All outcomes	Yes	100 women excluded postrandomisation - fully accounted for but no outcome data
Free of selective reporting?	Unclear	We did not assess the trial protocol.
Free of other bias?	Yes	No evidence for other bias.

Tripathi 1995

Methods	RCT.
Participants	Healthy women, uncomplicated singleton pregnancies at term requiring emergency CS under general anaesthesia N = 80.
Interventions	40 mg omeprazole IV at the time of decision to perform CS. 50 mg ranitidine IV at time of decision to perform CS.
Outcomes	Gastric volume and pH.
Notes
Risk of bias
Item	Authors℉ judgement	Description
Adequate sequence generation?	Unclear	Not described - “randomly assignedℍ.
Allocation concealment?	Unclear	Not described.
Blinding? All outcomes	Yes	Double-blind manner.
Incomplete outcome data addressed? All outcomes	Yes	All women accounted for.
Free of selective reporting?	Unclear	We did not assess the trial protocol.
Free of other bias?	Yes	No evidence of other bias.

Tryba 1983

Methods	RCT.
Participants	Pregnant women presenting for elective CS with no history of gastric problems N = 30.
Interventions	400 mg of oral cimetidine the night before surgery and 400 mg IM 120 min prior to anaesthesia (intervention group). No specific pre-operative medication was given (control group)
Outcomes	Gastric volume and gastric pH. Adverse events.
Notes
Risk of bias
Item	Authors’ judgement	Description
Adequate sequence generation?	Unclear	Not stated.
Allocation concealment?	Unclear	Not stated.
Blinding? All outcomes	Unclear	The translator reports blinding; however it is unclear who was blind to the treatment
Incomplete outcome data addressed? All outcomes	Yes	The translator reports ’0 dropouts’.
Free of selective reporting?	Unclear	We did not assess the trial protocol.
Free of other bias?	Unclear	No evidence of other bias but uncertain due to translation.

Wig 1987

Methods	RCT.
Participants	Pregnant women undergoing emergency CS under general anaesthesia N = 90.
Interventions	Sodium citrate 30 ml 0.3 M 15 min prior to induction via nasogastric tube (intervention group 1). Magnesium trisilicate 1.5 g dissolved in 15 ml of tap water, 15 min prior to induction via nasogastric tube (intervention group 2). 30 ml tap water via nasogastric tube, 15 min prior to induction of anaesthesia (comparison group)
Outcomes	Gastric pH measured pre-administration of Rx, postintubation and postextubation
Notes
Risk of bias
Item	Authors’ judgement	Description
Adequate sequence generation?	Unclear	Not described ’randomly allocated’.
Allocation concealment?	Unclear	Not described.
Blinding? All outcomes	No	Not described.
Incomplete outcome data addressed? All outcomes	Unclear	States randomised 30 to each group but N in each group for results not given
Free of selective reporting?	Unclear	We did not assess the trial protocol.
Free of other bias?	Yes	No evidence of other bias.

Yau 1992

Methods	RCT.
Participants	Chinese women undergoing emergency CS. N = 162.
Interventions	Ranitidine 150 mg every 6 hours + 30 ml 0.3 sodium citrate before induction. Omeprazole 40 mg 12 hourly + sodium citrate 30 ml 0.3 before induction. Omeprazole 40 mg 12 hourly only.
Outcomes	Gastric volume and gastric pH. At risk of aspiration: ph < 2.5 and volume > 25 ml
Notes	Continuous data presented in graphs for gastric pH and volume; means and SD not given
Risk of bias
Item	Authors’ judgement	Description
Adequate sequence generation?	Unclear	Randomised on admission to labour ward.
Allocation concealment?	Unclear	Not described.
Blinding? All outcomes	Unclear	Not described.
Incomplete outcome data addressed? All outcomes	Unclear	Not described.
Free of selective reporting?	Unclear	We did not assess the trial protocol.
Free of other bias?	Yes	No evidence of other bias.

Zoroglu 1999

Methods	RCT.
Participants	Women undergoing CS under general anaesthesia. N = 75.
Interventions	300 mg nizatidine (intervention group 1). 40 mg famotidine (intervention group 2). Nsaline (comparison group).
Outcomes	Postintubation and pre-extubation gastric pH and gastric volume. Arterial and umbilical blood gases. Apgar scores and 1 and 5 min
Notes
Risk of bias
Item	Authors’ judgement	Description
Adequate sequence generation?	Unclear	Not described.
Allocation concealment?	Unclear	Not described.
Blinding? All outcomes	Unclear	Not described.
Incomplete outcome data addressed? All outcomes	Unclear	Not enough data to assess.
Free of selective reporting?	Unclear	We did not assess the trial protocol.
Free of other bias?	Yes	No evidence for other bias.

Zue 1999

Methods	RCT.
Participants	Pregnant women presenting for emergency CS for acute fetal distress, pre-eclampsia and failed trial of labour N = 60.
Interventions	Oral effervescent ranitidine 150 mg. No treatment.
Outcomes	Gastric pH- measured with pH meter immediately postintubation and pre extubation
Notes
Risk of bias
Item	Authors’ judgement	Description
Adequate sequence generation?	Unclear	Not described.
Allocation concealment?	Unclear	Not described.
Blinding? All outcomes	No	No reports of blinding.
Incomplete outcome data addressed? All outcomes	Yes	No loss of participants reported.
Free of selective reporting?	Unclear	Due to translation of paper and we did not assess the trial protocol
Free of other bias?	Yes	No evidence of other bias.

CS: caesarean section

hr: hour

GA: gestational age

IM: intramuscular

IV: intravenous

ITT: intention to treat

M: molar

min: minute(s)

po: by mouth

pre-op: pre-operative

RCT: randomised controlled trial

SD: standard deviation

Characteristics of excluded studies [ordered by study ID]

Study	Reason for exclusion
Abboud 1984	Study compares two different antacids with each other, sodium citrate versus Gelusil (aluminium hydroxide and magnesium hydroxide)
Abouleish 1999	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Ackerman 1987	Study assessed drugs given for analgesia, not for reducing aspiration pneumonitis
Ackerman 1988	Study assessed drugs given for analgesia, not for reducing aspiration pneumonitis
Ackerman 1989	Study assessed drugs given for analgesia, not for reducing aspiration pneumonitis
Apiliogullari 2008	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Atkinson 1980	Not an RCT
Avramovic 1979	Investigated effect of post-CS intervention on abdominal distension
Ayorinde 2000	Study assessed drugs given for blood pressure control, not for reducing aspiration pneumonitis
Ayorinde 2001	Study assessed drugs given for blood pressure control, not for reducing aspiration pneumonitis
Belzarena 1993	Study assessed drugs given for blood pressure control, not for reducing aspiration pneumonitis
Bifarini 1990	Following translation, no useable data were presented.
Bifarini 1992	Could not use data as the standard deviations were not presented for the mean values
Birnbach 1993	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Biswas 2003	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Biwas 2002	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Bonhomme 2002	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Boone 2002	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Boschi 1984	Not an RCT; women were divided into groups.
Brock-Utne 1989	Not an RCT; women were allocated to groups.
Brody 2008	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Bylsma-Howell 1983	Not ITT.
Caba 1997	Outcomes assessed in the nausea and vomiting review.
Chan 1992	Study was a quasi-RCT.
Chan 1997	Study assessed drugs given for blood pressure control, not for reducing aspiration pneumonitis
Charuluxananan 2003	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Chaudhuri 2004	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Chen 2005	Study assessed acupressure for reducing nausea and vomiting, anxiety and pain in women post-CS, not for reducing aspiration pneumonitis
Cherian 2001	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Chestnut 1987	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Chestnut 1989	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Chung 1998	Study assessed postcaesarean analgesia.
Cohen 1983	No information on how women were allocated to groups.
Colman 1988	No information on how women were allocated to groups.
Connelly 1997	Study assessed drugs for reducing side effects of intrathecal opioids at CS
Cooper 2002	Study assessed drugs given for blood pressure control, not for reducing aspiration pneumonitis
Cowan 2002	Study assessed drugs given for analgesia, not for reducing aspiration pneumonitis
Dahlgren 1997	Study assessed drugs given for analgesia, not for reducing aspiration pneumonitis
Dailey 1985	Study assessed lignocaine given for analgesia, not for reducing aspiration pneumonitis
Dailey 1988	Study assessed lignocaine concentrations in the blood and no clinical outcomes assessed
Datta 1982	No information on how women were allocated to groups.
Dewan 1982	Not described as an RCT; women were assigned to groups.
Duggal 1998	Intervention looks at reducing nausea and vomiting not aspiration pneumonitis
Dundee 1979	No information on how women were allocated to groups.
Fan 1994	Studying the effect of different doses of bupivacaine on anaesthesia
Flynn 1989a	Study of effect of 400 mg cimetidine or 150 mg ranitidine or placebo on plasma levels of bupivacaine at CS
Flynn 1989b	Study of effect of 200 mg cimetidine plasma levels of lignocaine at CS
Flynn 1989c	Study of effect of 400 mg cimetidine or 150 mg ranitidine or placebo on plasma levels of lidocaine at CS
Fogarty 1992	Insufficient information provided. We wrote to authors but have not received a response
Freeman 1999	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Fujii 1998a	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Fujii 1998b	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Fujii 1999	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Fujii 2002	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Fujii 2004	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Gaiser 2002	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Ghods 2005	Study to test efficacy of postoperative supplemental oxygen in reducing the incidence of postoperative nausea and vomiting
Gutsche 1976	Assessing ephedrine for reducing hypotension of spinal anaesthesia
Habib 2006	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Harmon 2000	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Hildyard 2000	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Ho 1996	Study assessing P-6 acupressure on nausea and vomiting for post-CS pain relief
Ho 2006	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Hodgkinson 1983	Not ITT analysis for primary outcome and poor randomisation exclusion rates
Holdsworth 1974	Not an RCT
Holdsworth 1978	Quasi-RCT.
Holdsworth 1980	Not an RCT. Assessing women’s positions for GA.
Huang 1992	Not relevant for outcomes of this review.
Hunt 1989	Assessed fentanyl added to bupivacaine in spinal anaesthesia for effective anaesthesia but assessed Apgar scores
Imbeloni 1986	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Ishiyama 2001	Analgaesia study assessing effects of fentanyl versus flurbiprofen on nausea and vomiting
Kang 1982	Hypotension study assessing continuous infusion versus bolus injection of ephedrine - effect on nausea and vomiting
Kangas-Saarela 1990	Study assessed drugs given for blood pressure control, not for reducing aspiration pneumonitis
Kasodekar 2006	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
King 1998	Study assessed drugs given for blood pressure control not for reducing aspiration pneumonitis
Kjaer 2006	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Kocamanoglu 2005	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Kotelko 1989	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Lim 1991	Not randomised.
Lim 2001a	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Lim 2001b	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Loughrey 2002	Study assessed drugs given for blood pressure control not for reducing aspiration pneumonitis
Lussos 1992	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Mandell 1986	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Mandell 1992	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Manullang 2000	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Maranhao 1988	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
McCaughey 1981	Not a randomised study.
Mebazaa 2003	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Mukherjee 2006	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Murphy 1984	Study assessed the effect of IV metoclopramide on gastric emptying on women having elective CSs and those having emergency CSs studying both women given narcotics and those not given narcotics. Outcomes in this review not assessed
Ngan 2000	Study assessed drugs given for blood pressure control, not for reducing aspiration pneumonitis
Ngan 2001	Study assessed drugs given for blood pressure control, not for reducing aspiration pneumonitis
Ngan 2004a	Study assessed drugs given for blood pressure control, not for reducing aspiration pneumonitis
Ngan 2004b	Study assessed drugs given for blood pressure control, not for reducing aspiration pneumonitis
Nortcliffe 2003	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Numazaki 2000	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Numazaki 2003	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
O’Sullivan 1985	Data are presented as medians and the range and therefore cannot be used
O’Sullivan 1988	Study assessed the effect of H2 receptor antagonists on bupivacaine clearance in women undergoing elective CS under epidural anaesthesia
Olsen 1994	Study assessed drugs given for blood pressure control, not for reducing aspiration pneumonitis
Osman 1995	Wrote to authors asking for number of participants in each group so that the data could be used. No response
Ouyang 2002	Study on fentanyl for analgesia.
Owczarzak 1997	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Palmer 1991	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Palmer 1995	Study assessing fentanyl for pain relief.
Pan 1996	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Pan 2001	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Pan 2003	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Peixoto 2006	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Pellegrini 2001	Study assessing the analgesic effects of opioid antagonist - not included in protocol
Phillips 2007	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Prakash 2006	Study looking at analgesia.
Quiney 1995	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Qvist 1983	Not randomised.
Qvist 1985	Studied effect of placental transfer of cimetidine given prior to induction of anaesthesia
Ramanathan 1983	Study looking at preloading for blood pressure.
Ramin 1994	Study assessed drugs given for blood pressure control, not for reducing aspiration pneumonitis
Rout 1992	Study assessed drugs given for blood pressure control, not for reducing aspiration pneumonitis
Rudra 2004a	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Rudra 2004b	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Sanansilp 1998	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Santos 1984	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Sen 2001	Study of analgesics for postoperative pain relief after CS.
Seyedhejazi 2007	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Shende 1998	Study on intrathecal fentanyl in subarachnoid block for CS.
Siddik-Sayyid 2002	Study on fentanyl in subarachnoid block for CS.
Stein 1997	Intervention looks at reducing nausea and vomiting during CS, not aspiration pneumonitis
Stuart 1996	Analysis not by intention to treat.
Tarhan 2007	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Taylor 1966	Study not thought to be an RCT as it does not state how women were allocated to groups
Tettambel 1983	Quasi-RCT.
Tzeng 2000	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Ure 1999	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Vercauteren 2000	Study assessed drugs given for blood pressure control not for reducing aspiration pneumonitis
von Braun 1994	We couldn’t use the data as we were not given the number of participants that were included in each treatment arm
Wang 2001	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Weiss 1995	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis
Yazigi 2002	Study assessed interventions for reducing nausea and vomiting at CS, not for reducing aspiration pneumonitis

CS: caesarean section

GA: gestational age

ITT: intention to treat

IV: intravenous

RCT: randomised controlled trial

Characteristics of studies awaiting assessment [ordered by study ID]

Methods	RCT.
Participants	Pregnant women.
Interventions	Omeprazole. Famotidine. Ranitidine.
Outcomes	Maternal gastric pH and volume and neonatal gastric pH and volume
Notes	This study has been translated but there was insufficient information to allow data extraction. We are contacting authors for clarification

RCT: randomised controlled trial

DATA AND ANALYSES

Comparison 1. Antacids versus placebo/no treatment.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Mortality due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2 Morbidity due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3 Intragastric pH < 2.5 at intubation	2	108	Risk Ratio (M-H, Fixed, 95% CI)	0.17 [0.09, 0.32]
3.1 Elective CS	1	22	Risk Ratio (M-H, Fixed, 95% CI)	0.13 [0.03, 0.59]
3.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.3 Elective or emergency CS not specified	1	86	Risk Ratio (M-H, Fixed, 95% CI)	0.18 [0.09, 0.36]
4 Intragastric volume > 0.4ml/kg at intubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5 Nausea	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6 Vomiting	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7 Sedation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8 Restlessness	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9 Dystonic reactions	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10 Extrapyramidal symptoms	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11 Hypotension	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
12 Blood loss	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
13 Atonic uterus	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
14 Women’s satisfaction	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
15 Cord blood pH	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.1 Elective CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.2 Emergency CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.3 Elective or emergency CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
16 Apgar < 7 at 5 minutes	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
17 Neonatal assessment scores	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
18 Admission to neonatal intensive care unitNICU	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19 Initiation of breastfeeding	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
20 Duration of breastfeeding	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.1 Elective CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.2 Emergency CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.3 Elective or emergency CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
21 Intragastric pH < 2.5 at extubation	1	86	Risk Ratio (M-H, Fixed, 95% CI)	0.21 [0.09, 0.48]
21.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.3 Elective or emergency CS not specified	1	86	Risk Ratio (M-H, Fixed, 95% CI)	0.21 [0.09, 0.48]
22 Intragastric volume > 0.4ml/kg at extubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
23 Gastric volume post intubation (not pre-specified)	2	74	Mean Difference (IV, Random, 95% CI)	30.33 [−3.97, 64.62
23.1 Elective CS	2	74	Mean Difference (IV, Random, 95% CI)	30.33 [−3.97, 64.62
23.2 Emergency CS	0	0	Mean Difference (IV, Random, 95% CI)	Not estimable
23.3 Elective or Emergency CS not specified	0	0	Mean Difference (IV, Random, 95% CI)	Not estimable
24 Gastric pH post intubation (not pre-specified)	4	220	Mean Difference (IV, Fixed, 95% CI)	2.63 [2.29, 2.96]
24.1 Elective CS	2	74	Mean Difference (IV, Fixed, 95% CI)	2.91 [2.36, 3.45]
24.2 Emergency CS	1	60	Mean Difference (IV, Fixed, 95% CI)	2.74 [2.16, 3.32]
24.3 Elective or Emergnecy CS not specified	1	86	Mean Difference (IV, Fixed, 95% CI)	2.13 [1.51, 2.75]
25 At risk of aspiration (not pre-specified)	1	22	Risk Ratio (M-H, Fixed, 95% CI)	0.07 [0.00, 1.04]
25.1 Elective CS	1	22	Risk Ratio (M-H, Fixed, 95% CI)	0.07 [0.00, 1.04]
25.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
25.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
26 Gastric pH at extubation (not pre-specified)	2	146	Mean Difference (IV, Fixed, 95% CI)	2.04 [1.66, 2.42]
26.1 Elective CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
26.2 Emergency CS	1	60	Mean Difference (IV, Fixed, 95% CI)	2.15 [1.71, 2.59]
26.3 Elective or Emergency CS not specified	1	86	Mean Difference (IV, Fixed, 95% CI)	1.74 [1.02, 2.46]
27 Gastric volume post intubation >25ml (not pre-specified)	1	22	Risk Ratio (M-H, Fixed, 95% CI)	1.43 [0.88, 2.32]
27.1 Elective CS	1	22	Risk Ratio (M-H, Fixed, 95% CI)	1.43 [0.88, 2.32]
27.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
27.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable

Comparison 2. H₂ antagonists versus placebo/no treatment.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Mortality due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2 Morbidity due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3 Intragastric pH < 2.5 at intubation	2	170	Risk Ratio (M-H, Fixed, 95% CI)	0.09 [0.05, 0.18]
3.1 Elective CS	2	170	Risk Ratio (M-H, Fixed, 95% CI)	0.09 [0.05, 0.18]
3.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4 Intragastric volume > 0.4ml/kg at intubation	2	170	Risk Ratio (M-H, Random, 95% CI)	0.08 [0.01, 0.86]
4.1 Elective CS	2	170	Risk Ratio (M-H, Random, 95% CI)	0.08 [0.01, 0.86]
4.2 Emergency CS	0	0	Risk Ratio (M-H, Random, 95% CI)	Not estimable
4.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Random, 95% CI)	Not estimable
5 Nausea	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6 Vomiting	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7 Sedation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8 Restlessness	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9 Dystonic reactions	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10 Extrapyramidal symptoms	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11 Hypotension	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
12 Blood loss	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
13 Atonic uterus	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
14 Women’s satisfaction	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
15 Cord blood pH	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.1 Elective CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.2 Emergency CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.3 Elective or emergency CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
16 Apgar < 7 at 5 minutes	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
17 Neonatal assessment scores	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
18 Admission to NICU	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19 Initiation of breastfeeding	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
20 Duration of breastfeeding	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
21 Intragastric pH < 2.5 at extubation	1	30	Risk Ratio (M-H, Fixed, 95% CI)	0.08 [0.01, 0.56]
21.1 Elective CS	1	30	Risk Ratio (M-H, Fixed, 95% CI)	0.08 [0.01, 0.56]
21.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22 Intragastric volume > 20ml at extubation (not pre-specifed)	1	30	Risk Ratio (M-H, Fixed, 95% CI)	0.33 [0.11, 0.99]
22.1 Elective CS	1	30	Risk Ratio (M-H, Fixed, 95% CI)	0.33 [0.11, 0.99]
22.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
23 Gastric pH at intubation (not pre-specified)	3	160	Mean Difference (IV, Random, 95% CI)	3.31 [1.82, 4.81]
23.1 Elective CS	2	100	Mean Difference (IV, Random, 95% CI)	2.59 [2.04, 3.14]
23.2 Emergency CS	1	60	Mean Difference (IV, Random, 95% CI)	4.43 [3.97, 4.89]
23.3 Elective or Emergency CS not specified	0	0	Mean Difference (IV, Random, 95% CI)	Not estimable
24 Gastric pH at extubation (not pre-specified)	2	110	Mean Difference (IV, Random, 95% CI)	3.56 [2.25, 4.87]
24.1 Elective CS	1	50	Mean Difference (IV, Random, 95% CI)	2.86 [2.13, 3.59]
24.2 Emergency CS	1	60	Mean Difference (IV, Random, 95% CI)	4.20 [3.70, 4.70]
24.3 Elective or emergency CS not specified	0	0	Mean Difference (IV, Random, 95% CI)	Not estimable
25 At risk of aspiration post intubation (not pre-specified)	4	255	Risk Ratio (M-H, Random, 95% CI)	0.07 [0.01, 0.33]
25.1 Elective CS	4	255	Risk Ratio (M-H, Random, 95% CI)	0.07 [0.01, 0.33]
25.2 Emergency CS	0	0	Risk Ratio (M-H, Random, 95% CI)	Not estimable
25.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Random, 95% CI)	Not estimable
26 At risk of aspiration pre extubation (not pre-specified)	2	125	Risk Ratio (M-H, Fixed, 95% CI)	0.17 [0.01, 4.03]
26.1 Elective CS	2	125	Risk Ratio (M-H, Fixed, 95% CI)	0.17 [0.01, 4.03]
26.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
26.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
27 Gastric volume post intubation (not pre-specified)	2	100	Mean Difference (IV, Fixed, 95% CI)	−14.06 [−18.68, −9.45]
27.1 Elective CS	2	100	Mean Difference (IV, Fixed, 95% CI)	−14.06 [−18.68, −9.45]
27.2 Emergency CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
27.3 Emergency and elective CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
28 Gastric volume pre-extubation (not pre-specified)	1	50	Mean Difference (IV, Fixed, 95% CI)	−3.70 [−6.17,−1.23]
28.1 Elective CS	1	50	Mean Difference (IV, Fixed, 95% CI)	−3.70 [−6.17,−1.23]
28.2 Emergency CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
28.3 Emergency and elective CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable

Comparison 3. Proton pump antagonists versus placebo/no treatment.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Mortality due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2 Morbidity due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3 Intragastric pH < 2.5 at intubation	1	80	Risk Ratio (M-H, Fixed, 95% CI)	0.26 [0.14, 0.46]
3.1 Elective CS	1	80	Risk Ratio (M-H, Fixed, 95% CI)	0.26 [0.14, 0.46]
3.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4 Intragastric volume > 0.4ml/kg 1 at intubation		80	Risk Ratio (M-H, Fixed, 95% CI)	0.46 [0.19, 1.09]
4.1 Elective CS	1	80	Risk Ratio (M-H, Fixed, 95% CI)	0.46 [0.19, 1.09]
4.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5 Nausea	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6 Vomiting	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7 Sedation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8 Restlessness	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9 Dystonic reactions	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10 Extrapyramidal symptoms	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11 Hypotension	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
12 Blood loss	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
13 Atonic uterus	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
14 Women’s satisfaction	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
15 Cord blood pH	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.1 Elective CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.2 Emergency CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.3 Elective or emergency CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
16 Apgar < 7 at 5 minutes	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
17 Neonatal assessment scores	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
18 Admission to NICU	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19 Initiation of breastfeeding	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
20 Duration of breastfeeding	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
21 Intragastric pH > 2.5 at extubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22 Intragastric volume < 0.4ml/kg at extubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
23 Gastric pH at intubation (not pre-specified)	1	80	Mean Difference (IV, Fixed, 95% CI)	3.27 [2.82, 3.7
23.1 Elective CS	1	80	Mean Difference (IV, Fixed, 95% CI)	3.27 [2.82, 3.7
23.2 Emergency CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
23.3 Elective or emergency CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
24 At risk of aspiration (not pre-specified)	2	130	Risk Ratio (M-H, Random, 95% CI)	0.14 [0.03, 0.7
24.1 Elective CS	2	130	Risk Ratio (M-H, Random, 95% CI)	0.14 [0.03, 0.7
24.2 Emergency CS	0	0	Risk Ratio (M-H, Random, 95% CI)	Not estimable
24.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Random, 95% CI)	Not estimable
25 Gastric volume at intubation (not pre-specified)	1	80	Mean Difference (IV, Fixed, 95% CI)	−0.25 [−0.30, −0.20]
25.1 Elective CS	1	80	Mean Difference (IV, Fixed, 95% CI)	−0.25 [−0.30, −0.20]
25.2 Emergency CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
25.3 Emergency and elective CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
26 Gastric pH pre extubation (not pre-specified)	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
26.1 Elective CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
26.2 Emergency CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
26.3 Emergency and elective CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
27 Gastric volume pre extubation (not pre-specified)	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
27.1 Elective CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
27.2 Emergency CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
27.3 Emergency and elective CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable

Comparison 4. Prokinetic drugs versus placebo/no treatment.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Mortality due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2 Morbidity due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3 Intragastric pH > 2.5 at intubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4 Intragastric volume < 0.4ml/kg at intubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5 Nausea	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6 Vomiting	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7 Sedation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8 Restlessness	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9 Dystonic reactions	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10 Extrapyramidal symptoms	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11 Hypotension	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
12 Blood loss	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
13 Atonic uterus	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
14 Women’s satisfaction	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
15 Cord blood pH	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.1 Elective CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.2 Emergency CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.3 Elective or emergency CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
16 Apgar < 7 at 5 minutes	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
17 Neonatal assessment scores	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
18 Admission to NICU	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19 Initiation of breastfeeding	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
20 Duration of breastfeeding	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
21 Intragastric pH > 2.5 at extubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22 Intragastric volume < 0.4ml/kg at extubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
23 At risk of aspiration post intubation (not pre-specified)	1	50	Risk Ratio (M-H, Fixed, 95% CI)	0.67 [0.33, 1.35]
23.1 Elective CS	1	50	Risk Ratio (M-H, Fixed, 95% CI)	0.67 [0.33, 1.35]
23.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
23.3 Elective or emergency not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
24 At risk of aspiration pre-extubation (not pre-specified)	1	50	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
24.1 Elective CS	1	50	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
24.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
24.3 Elective or emergency nor specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable

Comparison 5. Non-pharmacological interventions versus placebo/no treatment.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Mortality due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2 Morbidity due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3 Intragastric pH < 2.5 at intubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4 Intragastric volume < 0.4ml/kg at intubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5 Nausea	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6 Vomiting	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7 Sedation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8 Restlessness	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9 Dystonic reactions	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10 Extrapyramidal symptoms	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11 Hypotension	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
12 Blood loss	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
13 Atonic uterus	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
14 Women’s satisfaction	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
15 Cord blood pH	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.1 Elective CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.2 Emergency CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.3 Elective or emergency CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
16 Apgar < 7 at 5 minutes	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
17 Neonatal assessment scores	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
18 Admission to NICU	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19 Initiation of breastfeeding	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
20 Duration of breastfeeding	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
21 Intragastric pH < 2.5 at extubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22 Intragastric volume < 0.4ml/kg at extubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
23 At risk of aspiration (not pre-specified)	1	40	Risk Ratio (M-H, Fixed, 95% CI)	0.5 [0.18, 1.40]
23.1 Elective CS	1	40	Risk Ratio (M-H, Fixed, 95% CI)	0.5 [0.18, 1.40]
23.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
23.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable

Comparison 6. Antacids + H₂ antagonists versus placebo/no treatment.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Mortality due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2 Morbidity due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3 Intragastric pH < 2.5 at intubation	1	89	Risk Ratio (M-H, Fixed, 95% CI)	0.02 [0.00, 0.15]
3.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.3 Elective or emergency CS not specified	1	89	Risk Ratio (M-H, Fixed, 95% CI)	0.02 [0.00, 0.15]
4 Intragastric volume < 0.4ml/kg at intubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5 Nausea	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6 Vomiting	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7 Sedation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8 Restlessness	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9 Dystonic reactions	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10 Extrapyramidal symptoms	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11 Hypotension	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
12 Blood loss	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
13 Atonic uterus	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
14 Women’s satisfaction	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
15 Cord blood pH	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.1 Elective CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.2 Emergency CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.3 Elective or emergency CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
16 Apgar < 7 at 5 minutes	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
17 Neonatal assessment scores	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
18 Admission to NICU	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19 Initiation of breastfeeding	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
20 Duration of breastfeeding	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
21 Intragastric pH < 2.5 at extubation	1	89	Risk Ratio (M-H, Fixed, 95% CI)	0.03 [0.00, 0.24]
21.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.3 Elective or emergency CS not specified	1	89	Risk Ratio (M-H, Fixed, 95% CI)	0.03 [0.00, 0.24]
22 Intragastric volume < 0.4ml/kg at extubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
23 Intragastric pH post intubation (not pre-specified)	1	89	Mean Difference (IV, Fixed, 95% CI)	2.82 [2.25, 3.39]
23.1 Elective CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
23.2 Emergency CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
23.3 Elective or emergency CS not specified	1	89	Mean Difference (IV, Fixed, 95% CI)	2.82 [2.25, 3.39]
24 Intragastric pH at extubation (not pre-specified)	1	89	Mean Difference (IV, Fixed, 95% CI)	2.54 [1.85, 3.23]
24.1 Emergency CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
24.2 Elective CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
24.3 Emeegency or elective CS not specified	1	89	Mean Difference (IV, Fixed, 95% CI)	2.54 [1.85, 3.23]

Comparison 7. H₂ antagonists + prokinetic drugs versus placebo/no treatment.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Mortality due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2 Morbidity due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3 Intragastric pH < 2.5 at intubation	1	50	Risk Ratio (M-H, Fixed, 95% CI)	0.03 [0.00, 0.48]
3.1 Elective CS	1	50	Risk Ratio (M-H, Fixed, 95% CI)	0.03 [0.00, 0.48]
3.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4 Intragastric volume < 0.4ml/kg at intubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5 Nausea	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6 Vomiting	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7 Sedation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8 Restlessness	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9 Dystonic reactions	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10 Extrapyramidal symptoms	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11 Hypotension	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
12 Blood loss	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
13 Atonic uterus	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
14 Women’s satisfaction	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
15 Cord blood pH	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.1 Elective CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.2 Emergency CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.3 Elective or emergency CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
16 Apgar < 7 at 5 minutes	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
17 Neonatal assessment scores	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
18 Admission to NICU	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19 Initiation of breastfeeding	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
20 Duration of breastfeeding	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
21 Intragastric pH > 2.5 at extubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22 Intragastric volume < 0.4ml/kg at extubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
23 Risk of aspiration (not pre-specified)	1	50	Risk Ratio (M-H, Fixed, 95% CI)	0.03 [0.00, 0.51]
23.1 Elective CS	1	50	Risk Ratio (M-H, Fixed, 95% CI)	0.03 [0.00, 0.51]
23.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
23.3 Emergency and elective cs not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
24 Gastric pH post intubation (not pre-specified)	1	50	Mean Difference (IV, Fixed, 95% CI)	3.17 [2.57, 3.77]
24.1 Elective CS	1	50	Mean Difference (IV, Fixed, 95% CI)	3.17 [2.57, 3.77]
24.2 Emergency CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
24.3 Emergency and elective CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
25 Gastric volume post intubation (not pre-specified)	1	50	Mean Difference (IV, Fixed, 95% CI)	−14.20 [−20.92, −7. 48]
25.1 Elective CS	1	50	Mean Difference (IV, Fixed, 95% CI)	−14.20 [−20.92, −7.48]
25.2 Emergency CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
25.3 Emergency and elective CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
26 Gastric volume <25ml after induction	1	50	Odds Ratio (M-H, Fixed, 95% CI)	5.63 [1.65, 19.23]
26.1 Elective CS	1	50	Odds Ratio (M-H, Fixed, 95% CI)	5.63 [1.65, 19.23]
26.2 Emergency CS	0	0	Odds Ratio (M-H, Fixed, 95% CI)	Not estimable
26.3 Elective or emergency CS not specified	0	0	Odds Ratio (M-H, Fixed, 95% CI)	Not estimable

Comparison 8. Antacids versus H₂ antagonists.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Mortality due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2 Morbidity due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3 Intragastric pH < 2.5 at intubation	2	135	Risk Ratio (M-H, Fixed, 95% CI)	0.07 [0.01, 0.52]
3.1 Elective CS	2	104	Risk Ratio (M-H, Fixed, 95% CI)	0.07 [0.01, 0.52]
3.2 Emergency CS	1	31	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4 Intragastric volume < 0.4ml/kg 0 at intubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5 Nausea	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6 Vomiting	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7 Sedation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8 Restlessness	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9 Dystonic reactions	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10 Extrapyramidal symptoms	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11 Hypotension	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
12 Blood loss	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
13 Atonic uterus	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
14 Women’s satisfaction	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
15 Cord blood pH	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.1 Elective CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.2 Emergency CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.3 Elective or emergency CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
16 Apgar < 7 at 5 minutes	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
17 Neonatal assessment scores	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
18 Admission to NICU	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19 Initiation of breastfeeding	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
20 Duration of breastfeeding	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
21 Intragastric pH > 2.5 at extubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22 Intragastric volume < 0.4ml/kg at extubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
23 At risk of aspiration (not pre-specified)	1	16	Risk Ratio (M-H, Fixed, 95% CI)	1.0 [0.18, 5.46]
23.1 Elective CS	1	16	Risk Ratio (M-H, Fixed, 95% CI)	1.0 [0.18, 5.46]
23.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
23.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
24 Gastric volume at intubation (not pre-specified)	3	102	Std. Mean Difference (IV, Random, 95% CI)	0.75 [0.34, 1.16]
24.1 Elective CS	3	102	Std. Mean Difference (IV, Random, 95% CI)	0.75 [0.34, 1.16]
24.2 Emergency CS	0	0	Std. Mean Difference (IV, Random, 95% CI)	Not estimable
24.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Random, 95% CI)	Not estimable
25 Gastric pH at intubation (not pre-specified)	1	24	Mean Difference (IV, Fixed, 95% CI)	−3.02 [−4.52, −1.52]
25.1 Elective CS	1	24	Mean Difference (IV, Fixed, 95% CI)	−3.02 [−4.52, −1.52]
25.2 Emergency CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
25.3 Elective or emergency CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
26 Gastric pH at extubation (not pre-specified)	1	24	Mean Difference (IV, Fixed, 95% CI)	−2.32 [−4.00, −0.64]
26.1 Elective CS	1	24	Mean Difference (IV, Fixed, 95% CI)	−2.32 [−4.00, −0.64]
26.2 Emergenct CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
26.3 Elective or emergency CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable

Comparison 9. Antacids versus prokinetic drugs.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Mortality due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2 Morbidity due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3 Intragastric pH > 2.5 at intubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4 Intragastric volume < 0.4ml/kg at intubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5 Nausea	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6 Vomiting	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7 Sedation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8 Restlessness	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9 Dystonic reactions	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10 Extrapyramidal symptoms	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11 Hypotension	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
12 Blood loss	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
13 Atonic uterus	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
14 Women’s satisfaction	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
15 Cord blood pH	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.1 Elective CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.2 Emergency CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.3 Elective or emergency CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
16 Apgar < 7 at 5 minutes	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
17 Neonatal assessment scores	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
18 Admission to NICU	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19 Initiation of breastfeeding	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
20 Duration of breastfeeding	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
21 Intragastric pH > 2.5 at extubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22 Intragastric volume < 0.4ml/kg at extubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable

Comparison 10. H₂ antagonists versus proton pump antagonists.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Mortality due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2 Morbidity due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3 Intragastric pH < 2.5 at intubation	1	120	Risk Ratio (M-H, Fixed, 95% CI)	0.39 [0.16, 0.97]
3.1 Elective CS	1	120	Risk Ratio (M-H, Fixed, 95% CI)	0.39 [0.16, 0.97]
3.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4 Intragastric volume < 0.4ml/kg at intubation	1	120	Risk Ratio (M-H, Fixed, 95% CI)	1.18 [1.03, 1.35]
4.1 Elective CS	1	120	Risk Ratio (M-H, Fixed, 95% CI)	1.18 [1.03, 1.35]
4.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5 Nausea	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6 Vomiting	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7 Sedation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8 Restlessness	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9 Dystonic reactions	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10 Extrapyramidal symptoms	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11 Hypotension	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
12 Blood loss	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
13 Atonic uterus	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
14 Women’s satisfaction	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
15 Cord blood pH	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.1 Elective CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.2 Emergency CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.3 Elective or emergency CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
16 Apgar < 7 at 5 minutes	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
17 Neonatal assessment scores	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
18 Admission to NICU	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19 Initiation of breastfeeding	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
20 Duration of breastfeeding	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
21 Intragastric pH > 2.5 at extubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22 Intragastric volume < 0.4ml/kg at extubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
23 At risk of aspiration (not pre-specified)	4	323	Risk Ratio (M-H, Random, 95% CI)	0.93 [0.20, 4.37]
23.1 Elective CS	2	141	Risk Ratio (M-H, Random, 95% CI)	0.79 [0.03, 23.67]
23.2 Emergency CS	2	182	Risk Ratio (M-H, Random, 95% CI)	1.04 [0.13, 8.32]
23.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Random, 95% CI)	Not estimable
24 Gastric pH post intubation (not pre-specified)	1	80	Mean Difference (IV, Fixed, 95% CI)	−0.68 [−1.28, −0.08]
24.1 Elective CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
24.2 Emergency CS	1	80	Mean Difference (IV, Fixed, 95% CI)	−0.68 [−1.28, −0.08]
24.3 Emergency and elective CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
25 Gastric volume post intubation (not pre-specified)	1	80	Mean Difference (IV, Fixed, 95% CI)	2.35 [−0.79, 5.49]
25.1 Elective CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
25.2 Emergency CS	1	80	Mean Difference (IV, Fixed, 95% CI)	2.35 [−0.79, 5.49]
25.3 Emergency and elective CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
26 Gastric pH pre extubation (not pre-specified)	1	80	Mean Difference (IV, Fixed, 95% CI)	−0.65 [−1.22, −0.08]
26.1 Elective CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
26.2 Emergency CS	1	80	Mean Difference (IV, Fixed, 95% CI)	−0.65 [−1.22, −0.08]
26.3 Emergency and elective CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
27 Gastric volume post extubation (not pre-specified)	1	80	Mean Difference (IV, Fixed, 95% CI)	−1.08 [−2.47, 0.31]
27.1 Elective CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
27.2 Emergency CS	1	80	Mean Difference (IV, Fixed, 95% CI)	−1.08 [−2.47, 0.31]
27.3 Emergency and elective CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable

Comparison 11. Antacids + H₂ antagonists versus antacids.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Mortality due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2 Morbidity due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3 Intragastric pH < 2.5 at intubation	1	119	Risk Ratio (M-H, Fixed, 95% CI)	0.12 [0.02, 0.92]
3.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.3 Elective or emergency CS not specified	1	119	Risk Ratio (M-H, Fixed, 95% CI)	0.12 [0.02, 0.92]
4 Intragastric volume < 0.4ml/kg at intubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5 Nausea	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6 Vomiting	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7 Sedation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8 Restlessness	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9 Dystonic reactions	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10 Extrapyramidal symptoms	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11 Hypotension	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
12 Blood loss	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
13 Atonic uterus	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
14 Women’s satisfaction	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
15 Cord blood pH	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.1 Elective CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.2 Emergency CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.3 Elective or emergency CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
16 Apgar < 7 at 5 minutes	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
17 Neonatal assessment scores	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
18 Admission to NICU	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19 Initiation of breastfeeding	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
20 Duration of breastfeeding	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
21 Intragastric pH < 2.5 at extubation	1	119	Risk Ratio (M-H, Fixed, 95% CI)	0.16 [0.02, 1.28]
21.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.3 Elective or emergency CS not specified	1	119	Risk Ratio (M-H, Fixed, 95% CI)	0.16 [0.02, 1.28]
22 Intragastric volume < 0.4ml/kg at extubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
23 Post Intubation pH (not pre-specified)	2	672	Mean Difference (IV, Random, 95% CI)	0.43 [0.07, 0.79]
23.1 Elective CS	0	0	Mean Difference (IV, Random, 95% CI)	Not estimable
23.2 Emergency CS	1	553	Mean Difference (IV, Random, 95% CI)	0.30 [0.14, 0.46]
23.3 Emergency or Elective CS non specified	1	119	Mean Difference (IV, Random, 95% CI)	0.69 [0.22, 1.16]
24 Pre extubation pH (not pre-specified)	2	597	Mean Difference (IV, Fixed, 95% CI)	0.71 [0.53, 0.89]
24.1 Elective CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
24.2 Emergency CS	1	478	Mean Difference (IV, Fixed, 95% CI)	0.70 [0.51, 0.89]
24.3 Elective or emergency CS non specified	1	119	Mean Difference (IV, Fixed, 95% CI)	0.80 [0.29, 1.31]
25 Post intubation gastric volume (not pre-specified)	1	586	Mean Difference (IV, Fixed, 95% CI)	−1.0 [−8.75, 6.75]
25.1 Elective CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
25.2 Emergency CS	1	586	Mean Difference (IV, Fixed, 95% CI)	−1.0 [−8.75, 6.75]
25.3 Elective or emergency CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
26 Pre-extubation gastric volume (not pre-specified)	1	568	Mean Difference (IV, Fixed, 95% CI)	−2.0 [−5.21, 1.21]
26.1 Elective CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
26.2 Emergency CS	1	568	Mean Difference (IV, Fixed, 95% CI)	−2.0 [−5.21, 1.21]
26.3 Elective or emergency CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
27 At risk of aspiration (not pre-specified)	1	595	Odds Ratio (M-H, Fixed, 95% CI)	0.10 [0.02, 0.45]
27.1 Elective CS	0	0	Odds Ratio (M-H, Fixed, 95% CI)	Not estimable
27.2 Emergency CS	1	595	Odds Ratio (M-H, Fixed, 95% CI)	0.10 [0.02, 0.45]
27.3 Elective or emergency CS not specified	0	0	Odds Ratio (M-H, Fixed, 95% CI)	Not estimable

Comparison 12. H₂ antagonists + prokinetic drugs versus antacids.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Mortality due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2 Morbidity due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3 Intragastric pH > 2.5 at intubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4 Intragastric volume < 0.4ml/kg at intubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5 Nausea	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6 Vomiting	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7 Sedation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8 Restlessness	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9 Dystonic reactions	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10 Extrapyramidal symptoms	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11 Hypotension	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
12 Blood loss	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
13 Atonic uterus	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
14 Women’s satisfaction	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
15 Cord blood pH	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.1 Elective CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.2 Emergency CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.3 Elective or emergency CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
16 Apgar < 7 at 5 minutes	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
17 Neonatal assessment scores	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
18 Admission to NICU	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19 Initiation of breastfeeding	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
20 Duration of breastfeeding	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
21 Intragastric pH > 2.5 at extubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22 Intragastric volume < 0.4ml/kg at extubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable

Comparison 13. Proton pump agonists + prokinetics versus proton pump agonists.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Mortality due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2 Morbidity due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3 Intragastric pH > 2.5 at intubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4 Intragastric volume < 0.4ml/kg at intubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5 Nausea	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6 Vomiting	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7 Sedation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8 Restlessness	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9 Dystonic reactions	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10 Extrapyramidal symptoms	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11 Hypotension	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
12 Blood loss	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
13 Atonic uterus	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
14 Women’s satisfaction	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
15 Cord blood pH	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.1 Elective CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.2 Emergency CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.3 Elective or emergency CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
16 Apgar < 7 at 5 minutes	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
17 Neonatal assessment scores	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
18 Admission to NICU	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19 Initiation of breastfeeding	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
20 Duration of breastfeeding	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
21 Intragastric pH > 2.5 at extubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22 Intragastric volume < 0.4ml/kg at extubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
23 At risk of aspiration post intubation (not pre-specified)	1	97	Odds Ratio (M-H, Fixed, 95% CI)	0.44 [0.11, 1.66]
23.1 Elective CS	1	97	Odds Ratio (M-H, Fixed, 95% CI)	0.44 [0.11, 1.66]
23.2 Emergency CS	0	0	Odds Ratio (M-H, Fixed, 95% CI)	Not estimable
23.3 Elective or emergency CS not specified	0	0	Odds Ratio (M-H, Fixed, 95% CI)	Not estimable
24 At risk of aspiration pre extubation (not pre specified)	1	94	Odds Ratio (M-H, Fixed, 95% CI)	0.66 [0.03, 16.70]
24.1 Elective CS	1	94	Odds Ratio (M-H, Fixed, 95% CI)	0.66 [0.03, 16.70]
24.2 Emergency CS	0	0	Odds Ratio (M-H, Fixed, 95% CI)	Not estimable
24.3 Elective and emergency CS not specified	0	0	Odds Ratio (M-H, Fixed, 95% CI)	Not estimable

Comparison 14. H₂ antagonist versus Tramadol.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Mortality due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2 Morbidity due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3 Intragastric pH < 2.5 at intubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4 Intragastric volume > 0.4ml/kg at intubation	1	90	Risk Ratio (M-H, Fixed, 95% CI)	5.0 [1.03, 24.28]
4.1 Elective CS	1	90	Risk Ratio (M-H, Fixed, 95% CI)	5.0 [1.03, 24.28]
4.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5 Nausea	1	60	Risk Ratio (M-H, Fixed, 95% CI)	1.38 [0.64, 2.93]
5.1 Elective CS	1	60	Risk Ratio (M-H, Fixed, 95% CI)	1.38 [0.64, 2.93]
5.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6 Vomiting	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.3 Emergency and elective CS non specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7 Sedation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8 Restlessness	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9 Dystonic reactions	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10 Extrapyramidal symptoms	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11 Hypotension	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
12 Blood loss	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
13 Atonic uterus	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
14 Women’s satisfaction	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
15 Cord blood pH	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.1 Elective CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.2 Emergency CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.3 Elective or emergency CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
16 Apgar score < 7 at 5 mins	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.1 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.2 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.3 Emergency and elective CS non specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
17 Neonatal assessment scores	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
18 Admission to NICU	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19 Initiation of breastfeeding	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
20 Duration of breastfeeding	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
21 Intragastric pH < 2.5 at extubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22 Intragastric volume > 0.4ml/kg at extubation	1	60	Risk Ratio (M-H, Fixed, 95% CI)	3.0 [0.33, 27.23]
22.1 Elective CS	1	60	Risk Ratio (M-H, Fixed, 95% CI)	3.0 [0.33, 27.23]
22.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
23 At risk post intubation (not pre-specified)	1	60	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
23.1 Elective CS	1	60	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
23.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
23.3 Emergency and elective CS non specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
24 At risk pre extubation (not pre-specified)	1	60	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
24.1 Elective CS	1	60	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
24.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
24.3 Emergency or elective CS non specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
25 Nausea 24hours post op (not pre-specified)	1	60	Risk Ratio (M-H, Fixed, 95% CI)	1.43 [0.63, 3.25]
25.1 Elective CS	1	60	Risk Ratio (M-H, Fixed, 95% CI)	1.43 [0.63, 3.25]
25.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
25.3 Emergency and elective CS non specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable

Comparison 15. Antacids + H₂ antagonists versus proton pump antagonists.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Mortality due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2 Morbidity due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3 Intragastric pH < 2.5 at intubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4 Intragastric volume > 0.4ml/kg at intubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5 Nausea	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6 Vomiting	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.3 Emergency and elective CS non specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7 Sedation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8 Restlessness	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9 Dystonic reactions	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10 Extrapyramidal symptoms	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11 Hypotension	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
12 Blood loss	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
13 Atonic uterus	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
14 Women’s satisfaction	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
15 Cord blood pH	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.1 Elective CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.2 Emergency CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.3 Elective or emergency CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
16 Apgar score < 7 at 5 mins	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.1 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.2 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.3 Emergency and elective CS non specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
17 Neonatal assessment scores	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
18 Admission to NICU	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19 Initiation of breastfeeding	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
20 Duration of breastfeeding	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
21 Intragastric pH < 2.5 at extubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22 Intragastric volume > 0.4ml/kg at extubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
23 At risk of aspiration (not pre-specified)	1	108	Risk Ratio (M-H, Fixed, 95% CI)	0.12 [0.02, 0.91]
23.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
23.2 Emergency CS	1	108	Risk Ratio (M-H, Fixed, 95% CI)	0.12 [0.02, 0.91]
23.3 Emergency and elective CS non specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable

Comparison 16. Proton pump antagonist + antacid versus proton pump antagonist.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Mortality due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2 Morbidity due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3 Intragastric pH < 2.5 at intubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4 Intragastric volume > 0.4ml/kg at intubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5 Nausea	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6 Vomiting	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.3 Emergency and elective CS non specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7 Sedation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.3 Elective or emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8 Restlessness not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9 Dystonic reactions	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10 Extrapyramidal symptoms	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11 Hypotension	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
12 Blood loss	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
13 Atonic uterus	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
14 Women’s satisfaction	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
15 Cord blood pH	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.1 Elective CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.2 Emergency CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.3 Elective or emergency CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
16 Apgar score < 7 at 5 mins	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.1 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.2 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.3 Emergency and elective CS non specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
17 Neonatal assessment scores	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
18 Admission to NICU	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19 Initiation of breastfeeding	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
20 Duration of breastfeeding	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
21 Intragastric pH < 2.5 at extubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22 Intragastric volume > 0.4ml/kg at extubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
23 Risk of aspiration (not pre-specified)	1	112	Risk Ratio (M-H, Fixed, 95% CI)	0.33 [0.10, 1.15]
23.1 Emergency CS	1	112	Risk Ratio (M-H, Fixed, 95% CI)	0.33 [0.10, 1.15]
23.2 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
23.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable

Comparison 17. H₂ antagonist + prokinetic versus H₂ antagonist.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Mortality due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
1.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2 Morbidity due to aspiration pneumonitis	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
2.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3 Intragastric pH < 2.5 at intubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
3.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4 Intragastric volume > 0.4ml/kg at intubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
4.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5 Nausea	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
5.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6 Vomiting	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
6.3 Emergency and elective CS non specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7 Sedation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
7.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8 Restlessness	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
8.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9 Dystonic reactions	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
9.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10 Extrapyramidal symptoms	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
10.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11 Hypotension	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
11.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
12 Blood loss	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
12.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
13 Atonic uterus	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
13.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
14 Women’s satisfaction	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
14.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
15 Cord blood pH	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.1 Elective CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.2 Emergency CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
15.3 Elective or emergency CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
16 Apgar score < 7 at 5 mins	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.1 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.2 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
16.3 Emergency and elective CS non specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
17 Neonatal assessment scores	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
17.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
18 Admission to NICU	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
18.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19 Initiation of breastfeeding	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
19.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
20 Duration of breastfeeding	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.1 Elective CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.2 Emergency CS	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
20.3 Elective or emergency CS not specified	0	0	Std. Mean Difference (IV, Fixed, 95% CI)	Not estimable
21 Intragastric pH < 2.5 at extubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
21.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22 Intragastric volume > 0.4ml/kg at extubation	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.1 Elective CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
22.3 Elective or emergency CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
23 Intragastric pH > 2.5 post intubation (not pre-specified)	1	50	Risk Ratio (M-H, Fixed, 95% CI)	1.04 [0.93, 1.16]
23.1 Elective CS	1	50	Risk Ratio (M-H, Fixed, 95% CI)	1.04 [0.93, 1.16]
23.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
23.3 Emergency and elective CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
24 Intragastric volume <0.4 ml/kg post intubation (not pre-specified)	1	50	Risk Ratio (M-H, Fixed, 95% CI)	0.86 [0.66, 1.12]
24.1 Elective CS	1	50	Risk Ratio (M-H, Fixed, 95% CI)	0.86 [0.66, 1.12]
24.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
24.3 Emergency and elective CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
25 Risk of aspiration (not pre-specified)	1	50	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
25.1 Elective CS	1	50	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
25.2 Emergency CS	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
25.3 Emergency and elective CS not specified	0	0	Risk Ratio (M-H, Fixed, 95% CI)	Not estimable
26 Gastric volume post intubation (not pre-specified)	1	50	Mean Difference (IV, Fixed, 95% CI)	1.30 [−3.17, 5.77]
26.1 Elective CS	1	50	Mean Difference (IV, Fixed, 95% CI)	1.30 [−3.17, 5.77]
26.2 Emergency CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
26.3 Emergency and elective CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
27 Gastric pH post intubation (not pre-specified)	1	50	Mean Difference (IV, Fixed, 95% CI)	0.59 [−0.14, 1.32]
27.1 Elective CS	1	50	Mean Difference (IV, Fixed, 95% CI)	0.59 [−0.14, 1.32]
27.2 Emergency CS	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable
27.3 Emergency and elective CS not specified	0	0	Mean Difference (IV, Fixed, 95% CI)	Not estimable

Analysis 1.3. Comparison 1 Antacids versus placebo/no treatment, Outcome 3 Intragastric pH < 2.5 at intubation.

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 1 Antacids versus placebo/no treatment

Outcome: 3 Intragastric pH < 2.5 at intubation

Analysis 1.21. Comparison 1 Antacids versus placebo/no treatment, Outcome 21 Intragastric pH < 2.5 at extubation.

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 1 Antacids versus placebo/no treatment

Outcome: 21 Intragastric pH < 2.5 at extubation

Analysis 1.23. Comparison 1 Antacids versus placebo/no treatment, Outcome 23 Gastric volume post intubation (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 1 Antacids versus placebo/no treatment

Outcome: 23 Gastric volume post intubation (not pre-specified)

Analysis 1.24. Comparison 1 Antacids versus placebo/no treatment, Outcome 24 Gastric pH post intubation (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 1 Antacids versus placebo/no treatment

Outcome: 24 Gastric pH post intubation (not pre-specified)

Analysis 1.25. Comparison 1 Antacids versus placebo/no treatment, Outcome 25 At risk of aspiration (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 1 Antacids versus placebo/no treatment

Outcome: 25 At risk of aspiration (not pre-specified)

Analysis 1.26. Comparison 1 Antacids versus placebo/no treatment, Outcome 26 Gastric pH at extubation (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 1 Antacids versus placebo/no treatment

Outcome: 26 Gastric pH at extubation (not pre-specified)

Analysis 1.27. Comparison 1 Antacids versus placebo/no treatment, Outcome 27 Gastric volume post intubation >25ml (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 1 Antacids versus placebo/no treatment

Outcome: 27 Gastric volume post intubation >25ml (not pre-specified)

Analysis 2.3. Comparison 2 H2 antagonists versus placebo/no treatment, Outcome 3 Intragastric pH < 2.5 at intubation.

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 2 H₂ antagonists versus placebo/no treatment

Outcome: 3 Intragastric pH < 2.5 at intubation

Analysis 2.4. Comparison 2 H2 antagonists versus placebo/no treatment, Outcome 4 Intragastric volume > 0.4ml/kg at intubation.

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 2 H₂ antagonists versus placebo/no treatment

Outcome: 4 Intragastric volume > 0.4ml/kg at intubation

Analysis 2.21. Comparison 2 H2 antagonists versus placebo/no treatment, Outcome 21 Intragastric pH < 2.5 at extubation.

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 2 H₂ antagonists versus placebo/no treatment

Outcome: 21 Intragastric pH < 2.5 at extubation

Analysis 2.22. Comparison 2 H2 antagonists versus placebo/no treatment, Outcome 22 Intragastric volume > 20ml at extubation (not pre-specifed).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 2 H₂ antagonists versus placebo/no treatment

Outcome: 22 Intragastric volume > 20ml at extubation (not pre-specifed)

Analysis 2.23. Comparison 2 H2 antagonists versus placebo/no treatment, Outcome 23 Gastric pH at intubation (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 2 H₂ antagonists versus placebo/no treatment

Outcome: 23 Gastric pH at intubation (not pre-specified)

Analysis 2.24. Comparison 2 H2 antagonists versus placebo/no treatment, Outcome 24 Gastric pH at extubation (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 2 H₂ antagonists versus placebo/no treatment

Outcome: 24 Gastric pH at extubation (not pre-specified)

Analysis 2.25. Comparison 2 H2 antagonists versus placebo/no treatment, Outcome 25 At risk of aspiration post intubation (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 2 H₂ antagonists versus placebo/no treatment

Outcome: 25 At risk of aspiration post intubation (not pre-specified)

Analysis 2.26. Comparison 2 H2 antagonists versus placebo/no treatment, Outcome 26 At risk of aspiration pre extubation (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 2 H₂ antagonists versus placebo/no treatment

Outcome: 26 At risk of aspiration pre extubation (not pre-specified)

Analysis 2.27. Comparison 2 H2 antagonists versus placebo/no treatment, Outcome 27 Gastric volume post intubation (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 2 H₂ antagonists versus placebo/no treatment

Outcome: 27 Gastric volume post intubation (not pre-specified)

Analysis 2.28. Comparison 2 H2 antagonists versus placebo/no treatment, Outcome 28 Gastric volume preextubation (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 2 H₂ antagonists versus placebo/no treatment

Outcome: 28 Gastric volume pre-extubation (not pre-specified)

Analysis 3.3. Comparison 3 Proton pump antagonists versus placebo/no treatment, Outcome 3 Intragastric pH < 2.5 at intubation.

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 3 Proton pump antagonists versus placebo/no treatment

Outcome: 3 Intragastric pH < 2.5 at intubation

Analysis 3.4. Comparison 3 Proton pump antagonists versus placebo/no treatment, Outcome 4 Intragastric volume > 0.4ml/kg at intubation.

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 3 Proton pump antagonists versus placebo/no treatment

Outcome: 4 Intragastric volume > 0.4ml/kg at intubation

Analysis 3.23. Comparison 3 Proton pump antagonists versus placebo/no treatment, Outcome 23 Gastric pH at intubation (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 3 Proton pump antagonists versus placebo/no treatment

Outcome: 23 Gastric pH at intubation (not pre-specified)

Analysis 3.24. Comparison 3 Proton pump antagonists versus placebo/no treatment, Outcome 24 At risk of aspiration (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 3 Proton pump antagonists versus placebo/no treatment

Outcome: 24 At risk of aspiration (not pre-specified)

Analysis 3.25. Comparison 3 Proton pump antagonists versus placebo/no treatment, Outcome 25 Gastric volume at intubation (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 3 Proton pump antagonists versus placebo/no treatment

Outcome: 25 Gastric volume at intubation (not pre-specified)

Analysis 4.23. Comparison 4 Prokinetic drugs versus placebo/no treatment, Outcome 23 At risk of aspiration post intubation (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 4 Prokinetic drugs versus placebo/no treatment

Outcome: 23 At risk of aspiration post intubation (not pre-specified)

Analysis 4.24. Comparison 4 Prokinetic drugs versus placebo/no treatment, Outcome 24 At risk of aspiration pre-extubation (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 4 Prokinetic drugs versus placebo/no treatment

Outcome: 24 At risk of aspiration pre-extubation (not pre-specified)

Analysis 5.23. Comparison 5 Non-pharmacological interventions versus placebo/no treatment, Outcome 23 At risk of aspiration (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 5 Non-pharmacological interventions versus placebo/no treatment

Outcome: 23 At risk of aspiration (not pre-specified)

Analysis 6.3. Comparison 6 Antacids + H2 antagonists versus placebo/no treatment, Outcome 3 Intragastric pH < 2.5 at intubation.

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 6 Antacids + H₂ antagonists versus placebo/no treatment

Outcome: 3 Intragastric pH < 2.5 at intubation

Analysis 6.21. Comparison 6 Antacids + H2 antagonists versus placebo/no treatment, Outcome 21 Intragastric pH < 2.5 at extubation.

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 6 Antacids + H₂ antagonists versus placebo/no treatment

Outcome: 21 Intragastric pH < 2.5 at extubation

Analysis 6.23. Comparison 6 Antacids + H2 antagonists versus placebo/no treatment, Outcome 23 Intragastric pH post intubation (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 6 Antacids + H₂ antagonists versus placebo/no treatment

Outcome: 23 Intragastric pH post intubation (not pre-specified)

Analysis 6.24. Comparison 6 Antacids + H2 antagonists versus placebo/no treatment, Outcome 24 Intragastric pH at extubation (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 6 Antacids + H₂ antagonists versus placebo/no treatment

Outcome: 24 Intragastric pH at extubation (not pre-specified)

Analysis 7.3. Comparison 7 H2 antagonists + prokinetic drugs versus placebo/no treatment, Outcome 3 Intragastric pH < 2.5 at intubation.

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 7 H₂ antagonists + prokinetic drugs versus placebo/no treatment

Outcome: 3 Intragastric pH < 2.5 at intubation

Analysis 7.23. Comparison 7 H2 antagonists + prokinetic drugs versus placebo/no treatment, Outcome 23 Risk of aspiration (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 7 H₂ antagonists + prokinetic drugs versus placebo/no treatment

Outcome: 23 Risk of aspiration (not pre-specified)

Analysis 7.24. Comparison 7 H2 antagonists + prokinetic drugs versus placebo/no treatment, Outcome 24 Gastric pH post intubation (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 7 H₂ antagonists + prokinetic drugs versus placebo/no treatment

Outcome: 24 Gastric pH post intubation (not pre-specified)

Analysis 7.25. Comparison 7 H2 antagonists + prokinetic drugs versus placebo/no treatment, Outcome 25 Gastric volume post intubation (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 7 H₂ antagonists + prokinetic drugs versus placebo/no treatment

Outcome: 25 Gastric volume post intubation (not pre-specified)

Analysis 7.26. Comparison 7 H2 antagonists + prokinetic drugs versus placebo/no treatment, Outcome 26 Gastric volume <25ml after induction.

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 7 H₂ antagonists + prokinetic drugs versus placebo/no treatment

Outcome: 26 Gastric volume <25ml after induction

Analysis 8.3. Comparison 8 Antacids versus H2 antagonists, Outcome 3 Intragastric pH < 2.5 at intubation.

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 8 Antacids versus H₂ antagonists

Outcome: 3 Intragastric pH < 2.5 at intubation

Analysis 8.23. Comparison 8 Antacids versus H2 antagonists, Outcome 23 At risk of aspiration (not prespecified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 8 Antacids versus H₂ antagonists

Outcome: 23 At risk of aspiration (not pre-specified)

Analysis 8.24. Comparison 8 Antacids versus H2 antagonists, Outcome 24 Gastric volume at intubation (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 8 Antacids versus H₂ antagonists

Outcome: 24 Gastric volume at intubation (not pre-specified)

Analysis 8.25. Comparison 8 Antacids versus H2 antagonists, Outcome 25 Gastric pH at intubation (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 8 Antacids versus H₂ antagonists

Outcome: 25 Gastric pH at intubation (not pre-specified)

Analysis 8.26. Comparison 8 Antacids versus H2 antagonists, Outcome 26 Gastric pH at extubation (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 8 Antacids versus H₂ antagonists

Outcome: 26 Gastric pH at extubation (not pre-specified)

Analysis 10.3. Comparison 10 H2 antagonists versus proton pump antagonists, Outcome 3 Intragastric pH < 2.5 at intubation.

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 10 H₂ antagonists versus proton pump antagonists

Outcome: 3 Intragastric pH < 2.5 at intubation

Analysis 10.4. Comparison 10 H2 antagonists versus proton pump antagonists, Outcome 4 Intragastric volume < 0.4ml/kg at intubation.

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 10 H₂ antagonists versus proton pump antagonists

Outcome: 4 Intragastric volume < 0.4ml/kg at intubation

Analysis 10.23. Comparison 10 H2 antagonists versus proton pump antagonists, Outcome 23 At risk of aspiration (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 10 H₂ antagonists versus proton pump antagonists

Outcome: 23 At risk of aspiration (not pre-specified)

Analysis 10.24. Comparison 10 H2 antagonists versus proton pump antagonists, Outcome 24 Gastric pH post intubation (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 10 H₂ antagonists versus proton pump antagonists

Outcome: 24 Gastric pH post intubation (not pre-specified)

Analysis 10.25. Comparison 10 H2 antagonists versus proton pump antagonists, Outcome 25 Gastric volume post intubation (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 10 H₂ antagonists versus proton pump antagonists

Outcome: 25 Gastric volume post intubation (not pre-specified)

Analysis 10.26. Comparison 10 H2 antagonists versus proton pump antagonists, Outcome 26 Gastric pH pre extubation (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 10 H₂ antagonists versus proton pump antagonists

Outcome: 26 Gastric pH pre extubation (not pre-specified)

Analysis 10.27. Comparison 10 H2 antagonists versus proton pump antagonists, Outcome 27 Gastric volume post extubation (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 10 H₂ antagonists versus proton pump antagonists

Outcome: 27 Gastric volume post extubation (not pre-specified)

Analysis 11.3. Comparison 11 Antacids + H2 antagonists versus antacids, Outcome 3 Intragastric pH < 2.5 at intubation.

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 11 Antacids + H₂ antagonists versus antacids

Outcome: 3 Intragastric pH < 2.5 at intubation

Analysis 11.21. Comparison 11 Antacids + H2 antagonists versus antacids, Outcome 21 Intragastric pH < 2.5 at extubation.

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 11 Antacids + H₂ antagonists versus antacids

Outcome: 21 Intragastric pH < 2.5 at extubation

Analysis 11.23. Comparison 11 Antacids + H2 antagonists versus antacids, Outcome 23 Post Intubation pH (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 11 Antacids + H₂ antagonists versus antacids

Outcome: 23 Post Intubation pH (not pre-specified)

Analysis 11.24. Comparison 11 Antacids + H2 antagonists versus antacids, Outcome 24 Pre extubation pH (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 11 Antacids + H₂ antagonists versus antacids

Outcome: 24 Pre extubation pH (not pre-specified)

Analysis 11.25. Comparison 11 Antacids + H2 antagonists versus antacids, Outcome 25 Post intubation gastric volume (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 11 Antacids + H₂ antagonists versus antacids

Outcome: 25 Post intubation gastric volume (not pre-specified)

Analysis 11.26. Comparison 11 Antacids + H2 antagonists versus antacids, Outcome 26 Pre-extubation gastric volume (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 11 Antacids + H₂ antagonists versus antacids

Outcome: 26 Pre-extubation gastric volume (not pre-specified)

Analysis 11.27. Comparison 11 Antacids + H2 antagonists versus antacids, Outcome 27 At risk of aspiration (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 11 Antacids + H₂ antagonists versus antacids

Outcome: 27 At risk of aspiration (not pre-specified)

Analysis 13.23. Comparison 13 Proton pump agonists + prokinetics versus proton pump agonists, Outcome 23 At risk of aspiration post intubation (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 13 Proton pump agonists + prokinetics versus proton pump agonists

Outcome: 23 At risk of aspiration post intubation (not pre-specified)

Analysis 13.24. Comparison 13 Proton pump agonists + prokinetics versus proton pump agonists, Outcome 24 At risk of aspiration pre extubation (not pre specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 13 Proton pump agonists + prokinetics versus proton pump agonists

Outcome: 24 At risk of aspiration pre extubation (not pre specified)

Analysis 14.4. Comparison 14 H2 antagonist versus Tramadol, Outcome 4 Intragastric volume > 0.4ml/kg at intubation.

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 14 H₂ antagonist versus Tramadol

Outcome: 4 Intragastric volume > 0.4ml/kg at intubation

Analysis 14.5. Comparison 14 H2 antagonist versus Tramadol, Outcome 5 Nausea.

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 14 H₂ antagonist versus Tramadol

Outcome: 5 Nausea

Analysis 14.22. Comparison 14 H2 antagonist versus Tramadol, Outcome 22 Intragastric volume > 0.4ml/kg at extubation.

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 14 H₂ antagonist versus Tramadol

Outcome: 22 Intragastric volume > 0.4ml/kg at extubation

Analysis 14.23. Comparison 14 H2 antagonist versus Tramadol, Outcome 23 At risk post intubation (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 14 H₂ antagonist versus Tramadol

Outcome: 23 At risk post intubation (not pre-specified)

Analysis 14.24. Comparison 14 H2 antagonist versus Tramadol, Outcome 24 At risk pre extubation (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 14 H₂ antagonist versus Tramadol

Outcome: 24 At risk pre extubation (not pre-specified)

Analysis 14.25. Comparison 14 H2 antagonist versus Tramadol, Outcome 25 Nausea 24hours post op (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 14 H₂ antagonist versus Tramadol

Outcome: 25 Nausea 24hours post op (not pre-specified)

Analysis 15.23. Comparison 15 Antacids + H2 antagonists versus proton pump antagonists, Outcome 23 At risk of aspiration (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 15 Antacids + H₂ antagonists versus proton pump antagonists

Outcome: 23 At risk of aspiration (not pre-specified)

Analysis 16.23. Comparison 16 Proton pump antagonist + antacid versus proton pump antagonist, Outcome 23 Risk of aspiration (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 16 Proton pump antagonist + antacid versus proton pump antagonist

Outcome: 23 Risk of aspiration (not pre-specified)

Analysis 17.23. Comparison 17 H2 antagonist + prokinetic versus H2 antagonist, Outcome 23 Intragastric pH > 2.5 post intubation (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 17 H₂ antagonist + prokinetic versus H₂ antagonist

Outcome: 23 Intragastric pH > 2.5 post intubation (not pre-specified)

Analysis 17.24. Comparison 17 H2 antagonist + prokinetic versus H2 antagonist, Outcome 24 Intragastric volume <0.4 ml/kg post intubation (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 17 H₂ antagonist + prokinetic versus H₂ antagonist

Outcome: 24 Intragastric volume <0.4 ml/kg post intubation (not pre-specified)

Analysis 17.25. Comparison 17 H2 antagonist + prokinetic versus H2 antagonist, Outcome 25 Risk of aspiration (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 17 H₂ antagonist + prokinetic versus H₂ antagonist

Outcome: 25 Risk of aspiration (not pre-specified)

Analysis 17.26. Comparison 17 H2 antagonist + prokinetic versus H2 antagonist, Outcome 26 Gastric volume post intubation (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 17 H₂ antagonist + prokinetic versus H₂ antagonist

Outcome: 26 Gastric volume post intubation (not pre-specified)

Analysis 17.27. Comparison 17 H2 antagonist + prokinetic versus H2 antagonist, Outcome 27 Gastric pH post intubation (not pre-specified).

Review: Interventions at caesarean section for reducing the risk of aspiration pneumonitis

Comparison: 17 H₂ antagonist + prokinetic versus H₂ antagonist

Outcome: 27 Gastric pH post intubation (not pre-specified)

HISTORY

Date	Event	Description
11 April 2008	New citation required and major changes	An editorial decision was taken to split the review into two: those interventions that could be given before surgery to reduce aspiration pneumonitis and those given during or after caesarean section (CS) to reduce nausea and vomiting. We have, therefore, updated the title and the scope of the previously published protocol (Paranjothy 2004) to reflect this decision.
18 February 2008	Amended	Converted to new review format.

DIFFERENCES BETWEEN PROTOCOL AND REVIEW

1. The title was changed from ’Drugs at caesarean section for preventing nausea, vomiting and aspiration pneumonitis’ to ’Interventions at caesarean section for reducing aspiration pneumonitis’ because we wished to include complimentary medicines and mechanical methods (however, we found no studies). In addition, it was felt that the interventions to reduce nausea and vomiting during caesarean section should be a separate review. This second review will look at the effect of ’Interventions given during caesarean section to reduce nausea and vomiting’.

2. We modified the ’Types of participants’ from ’Healthy pregnant women with an uncomplicated singleton pregnancy at term undergoing elective or emergency caesarean section under general or regional anaesthesia’ to ’Pregnant women undergoing elective or emergency caesarean section under general or regional anaesthesia’ because we felt the interventions needed should be applicable to a wider range of women.

3. We removed reference to route of administration in the inclusion criteria. Relevent studies will be included regardless of the route of administration of the trial medication. A comparison of the efficacy of different routes of administration will be included in subgroup analysis if sufficient data exist.

4. We removed the pharmacological and non-pharmacological subgroups because we felt the interventions should be considered more individually. We added elective caesarean section and emergency caesarean section subgroups because we felt the outcomes may be different in these two differing situations.

5. Several papers reported gastric volume and pH as continuous outcomes, and ’at risk of aspiration’. These were not pre-specified in our protocol but we have included them in the review as they are informative. In the protocol we had prespecified dichotomous outcomes for gastric pH as greater than 2.5, however we changed this to pH less than 2.5 as this is what the majority of papers have reported, and is intuitively easier to interpret.

6. We have taken out general versus regional anaesthesia as a sub-group comparison as all the RCTs that investigate this outcome were in women who had general anaesthesia.

7. We have modified the wording in the methods sections for ’Assessment of heterogeneity’, ’Assessment of reporting bias’ and ’Data synthesis’ to update them with the new methods being used by the group, developed in conjunction with the group’s statistician, Simon Gates, and Richard Riley. We have used these new methods in the review.