Interventions for treating genital Chlamydia trachomatis infection in pregnancy

Catherine Cluver; Natalia Novikova; David OA Eriksson; Kevin Bengtsson; Göran K Lingman

doi:10.1002/14651858.CD010485.pub2

. 2017 Sep 22;2017(9):CD010485. doi: 10.1002/14651858.CD010485.pub2

Interventions for treating genital Chlamydia trachomatis infection in pregnancy

Catherine Cluver ^1,^✉, Natalia Novikova ¹, David OA Eriksson ², Kevin Bengtsson ², Göran K Lingman ³

Editor: Cochrane Pregnancy and Childbirth Group

PMCID: PMC6483758 PMID: 28937705

Abstract

Background

Genital Chlamydia trachomatis (C.trachomatis) infection may lead to pregnancy complications such as miscarriage, preterm labour, low birthweight, preterm rupture of membranes, increased perinatal mortality, postpartum endometritis, chlamydial conjunctivitis and C.trachomatis pneumonia.This review supersedes a previous review on this topic.

Objectives

To establish the most efficacious and best‐tolerated therapy for treatment of genital chlamydial infection in preventing maternal infection and adverse neonatal outcomes.

Search methods

We searched the Cochrane Pregnancy and Childbirth Group’s Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (26 June 2017) and reference lists of retrieved studies.

Selection criteria

Randomised controlled trials (RCTs) as well as studies published in abstract form assessing interventions for treating genital C.trachomatis infection in pregnancy. Cluster‐RCTs were also eligible for inclusion but none were identified. Quasi‐randomised trials and trials using cross‐over design are not eligible for inclusion in this review.

Data collection and analysis

Two review authors independently assessed studies for inclusion, assessed trial quality and extracted the data using the agreed form. Data were checked for accuracy. Evidence was assessed using the GRADE approach.

Main results

We included 15 trials (involving 1754 women) although our meta‐analyses were based on fewer numbers of studies/women. All of the included studies were undertaken in North America from 1982 to 2001. Two studies were low risk of bias in all domains, all other studies had varying risk of bias. Four other studies were excluded and one study is ongoing.

Eight comparisons were included in this review; three compared antibiotic (erythromycin, clindamycin, amoxicillin) versus placebo; five compared an antibiotic versus another antibiotic (erythromycin, clindamycin, amoxicillin, azithromycin). No study reported different antibiotic regimens.

Microbiological cure (primary outcome)

Antibiotics versus placebo: Erythromycin (average risk ratio (RR) 2.64, 95% confidence interval (CI) 1.60 to 4.38; two trials, 495 women; I² = 68%; moderate‐certainty evidence), and clindamycin (RR 4.08, 95% CI 2.35 to 7.08; one trial, 85 women;low‐certainty evidence) were associated with improved microbiological cure compared to a placebo control. In one very small trial comparing amoxicillin and placebo, the results were unclear, but the evidence was graded very low (RR 2.00, 95% CI 0.59 to 6.79; 15 women).

One antibiotic versus another antibiotic: Amoxicillin made little or no difference in microbiological cure in comparison to erythromycin (RR 0.97, 95% CI 0.93 to 1.01; four trials, 466 women; high‐certainty evidence), probably no difference compared to clindamycin (RR 0.96, 95% CI 0.89 to 1.04; one trial, 101 women; moderate‐quality evidence), and evidence is very low certainty when compared to azithromycin so the effect is not certain (RR 0.89, 95% CI 0.71 to 1.12; two trials, 144 women; very low‐certainty evidence). Azithromycin versus erythromycin (average RR 1.11, 95% CI 1.00 to 1.23; six trials, 374 women; I² = 53%; moderate‐certainty evidence) probably have similar efficacy though results appear to favour azithromycin. Clindamycin versus erythromycin (RR 1.06, 95% CI 0.97 to 1.15; two trials, 173 women; low‐certainty evidence) may have similar numbers of women with a microbiological cure between groups.

Evidence was downgraded for design limitations, inconsistency, and imprecision in effect estimates.

Side effects of the treatment (maternal) (secondary outcome)

Antibiotics versus placebo: side effects including nausea, vomiting, and abdominal pain, were reported in two studies (495 women) but there was no clear evidence whether erythromycin was associated with more side effects than placebo and a high level of heterogeneity (I² = 78%) was observed (average RR 2.93, 95% CI 0.36 to 23.76). There was no clear difference in the number of women experiencing side effects when clindamycin was compared to placebo in one small study (5/41 versus 1/44) (RR 6.35, 95% CI 0.38 to 107.45, 62 women). The side effects reported were mostly gastrointestinal and also included resolving skin rashes.

One antibiotic versus another antibiotic: There was no clear difference in incidence of side effects (including nausea, vomiting, diarrhoea and abdominal pain) when amoxicillin was compared to azithromycin based on data from one small study (36 women) (RR 0.56, 95% CI 0.24 to 1.31).

However, amoxicillin was associated with fewer side effects compared to erythromycin with data from four trials (513 women) (RR 0.31, 95% CI 0.21 to 0.46; I² = 27%). Side effects included nausea, vomiting, diarrhoea, abdominal cramping, rash, and allergic reaction.

Both azithromycin (RR 0.24, 95% CI 0.17 to 0.34; six trials, 374 women) and clindamycin (RR 0.44, 95% CI 0.22 to 0.87; two trials, 183 women) were associated with a lower incidence of side effects compared to erythromycin. These side effects included nausea, vomiting, diarrhoea and abdominal cramping.

One small study (101 women) reported there was no clear difference in the number of women with side effects when amoxicillin was compared with clindamycin (RR 0.57, 95% CI 0.14 to 2.26; 107 women). The side effects reported included rash and gastrointestinal complaints.

Other secondary outcomes

Single trials reported data on repeated infections, preterm birth, preterm rupture of membranes, perinatal mortality and low birthweight and found no clear differences between treatments.

Many of this review's secondary outcomes were not reported in the included studies.

Authors' conclusions

Treatment with antibacterial agents achieves microbiological cure from C.trachomatis infection during pregnancy. There was no apparent difference between assessed agents (amoxicillin, erythromycin, clindamycin, azithromycin) in terms of efficacy (microbiological cure and repeat infection) and pregnancy complications (preterm birth, preterm rupture of membranes, low birthweight). Azithromycin and clindamycin appear to result in fewer side effects than erythromycin.

All of the studies in this review were conducted in North America, which may limit the generalisability of the results. In addition, study populations may differ in low‐resource settings and these results are therefore only applicable to well‐resourced settings. Furthermore, the trials in this review mainly took place in the nineties and early 2000's and antibiotic resistance may have changed since then.

Further well‐designed studies, with appropriate sample sizes and set in a variety of settings, are required to further evaluate interventions for treating C.trachomatis infection in pregnancy and determine which agents achieve the best microbiological cure with the least side effects. Such studies could report on the outcomes listed in this review.

Plain language summary

Treatment of genital Chlamydia trachomatis infection in pregnancy

What is the issue?

This review aimed to assess whether the treatment of chlamydial infection during pregnancy cured the infection and prevented complications to the women and babies without causing side effects. This new review supersedes an earlier review on this topic.

Why is this important?

Chlamydia trachomatis is a bacterial infection which is sexually transmitted. It is more common in younger women. Women may have the infection without knowing it. In pregnant women, genital Chlamydia trachomatis can cause pregnancy complications such as preterm labour, preterm birth, premature rupture of the membranes, low birthweight of infants, and infection in the uterus after giving birth. Babies who acquire Chlamydia trachomatis during birth can develop infection of the lungs and the eyes.

Finding an effective treatment with minimal side effects is extremely important considering the complications that can occur with untreated Chlamydia trachomatis infection in pregnancy.

What evidence did we find?

We searched for evidence (June 2017) and included 15 studies in the review. The studies had a mixed risk of bias and were of limited quality, often with small numbers of participants. Three studies compared antibiotics (erythromycin, clindamycin, and amoxicillin) with placebo. The other studies compared different antibiotics with each other.

All of the studies reported on curing chlamydia, based on the elimination of the bacteria, with an antibiotic. Erythromycin (moderate‐quality evidence from two studies, 495 women) and clindamycin (low‐quality evidence from one study, 85 women) appeared to be more effective than placebo. The quality of the evidence for amoxicillin versus placebo (one study 15 women) was very low so we cannot be certain of the results.

When comparing different antibiotics with each other, no one antibiotic was substantially better than another at curing chlamydia in the studies that we examined: amoxicillin versus azithromycin (very low‐quality evidence from two studies, 144 women), amoxicillin versus erythromycin (high‐quality evidence from four studies, 466 women), azithromycin versus erythromycin (moderate‐quality evidence from six studies, 374 women), clindamycin versus erythromycin (low‐quality evidence from two studies, 173 women), amoxicillin versus clindamycin (moderate‐quality evidence from one study, 101 women). Only single trials assessed repeated infections, preterm birth, preterm rupture of membranes, perinatal mortality and low birthweight and found there were no clear differences between the different types of antibiotics examined.

Side effects were more common with erythromycin (two studies, 495 women) and clindamycin (one study, 85 women) than with placebo. Amoxicillin resulted in fewer side effects than azithromycin (one study, 36 women) or erythromycin (four studies, 513 women), and azithromycin caused fewer side effects than erythromycin (six studies, 374 women). Amoxicillin and clindamycin produced a similar number of side effects in one study (107 women).

What does this mean?

Treatment of chlamydia infection with antibiotics appears to be effective during pregnancy. There is no clear difference between amoxicillin, erythromycin, clindamycin, azithromycin in curing the infection or preterm birth, preterm rupture of membranes, and low birthweight. Azithromycin and clindamycin appear to result in fewer side effects than erythromycin.

The included studies were all carried out in North America. Chlamydia testing remains a problem in low‐resource settings because of its costs. We conclude that well‐designed studies of appropriate sample size, in different settings, are needed to further assess the effects of treatment of chlamydia infection in pregnancy. Resistance to the tested antibiotics could have changed since the studies included in this review were conducted. In particular, future research could report on the outcomes of focus in this review and target those antibiotics, such as amoxicillin and clindamycin, which may be effective in curing chlamydia with the least side effects.

Summary of findings

Background

The prevalence of chlamydial infection in pregnancy is between 2% to 30% depending on the patient's age and risk factors (Berggren 2011; Much 1991). It is particularly common in women younger than 25 years of age (Walker 2012). Genital Chlamydia trachomatis (C.trachomatis) infection has been shown to be associated with pregnancy complications such as miscarriage (Nigro 2011), preterm labour (Pararas 2006; Rours 2011), low birthweight (Attenburrow 1985) and increased perinatal mortality (Silva 2011). There may also be an association with preterm rupture of membranes (Blas 2007) and postpartum endometritis (Ismail 1987). If the mother is untreated, 20% to 50% of newborn babies may develop chlamydial conjunctivitis (Kakar 2010), and another 10% to 20% may develop C.trachomatis pneumonia (Rours 2009). Vaginal birth is associated with the highest risk of transmission of chlamydial infection, however, there is a small risk of acquiring the infection even in infants born by caesarean section with premature rupture of membranes and intact membranes (Pammi 2012; Yu 2009).

Genital C.trachomatis infection is detected by nucleic acid amplification test (NAAT) on the specimens of genital secretions or urine. This test has replaced tissue culture of C.trachomatis (Jespersen 2005).

Description of the condition

Genital C.trachomatis infection is a common bacterial sexually transmitted infection. The majority of women infected with this bacteria are asymptomatic and, therefore, may be more likely to transmit the infection because they do not seek treatment for the infection, which may result in a longer duration of the infection. The sequelae of C.trachomatis genital infection range from cervicitis to pelvic inflammatory disease, perihepatitis, ectopic pregnancy and infertility (Zenilman 2012). We have described complications of pregnancy and diseases of newborn related to genital Chlamydia infection in the Background section above.

C.trachomatis is a small gram‐negative intracellular bacterium with a two‐phased life‐cycle, which includes the form that infects new cells, (e.g. the small elementary body) and the active form (e.g. the reticulate body). The life‐cycle is about two to three days, and, therefore, sustained high serum minimum inhibitory concentration of antimicrobial agents is needed to achieve eradication of the infection, which can be achieved by long‐acting antimicrobials treatment or prolonged treatment. The incubation period of C.trachomatis infection varies between seven and 14 days (Zenilman 2012).

Description of the intervention

There are various treatment regimens for the management of chlamydial infection during pregnancy, however, there is no consensus on the most effective and safest option. In some, the hosts' immune system may even clear the infection.

According to the Centers for Disease Control and Prevention (CDC) guideline followed by many countries around the world, the recommended regimens for treatment of genital chlamydial infection in pregnancy are azithromycin (1 g orally given as a single dose) or amoxicillin (500 mg orally three times daily for seven days) (Workowski 2010). The alternative regimen according to the CDC guideline is erythromycin (500 mg or 250 mg orally four times daily for seven days), or erythromycin ethylsuccinate (800 mg orally four times daily for seven days, or 400 mg orally four times daily for 14 days) (Workowski 2010). Erythromycin is associated with a high degree of gastrointestinal side effects (primarily nausea) and the compliance may be an issue in such cases (Workowski 2010).    Women who present in labour but were not treated for a prior positive chlamydial test are advised to be treated immediately with one of the above regimens. However, such late treatment is unlikely to substantially decrease the risk of transmission of Chlamydia to the newborn.

Clindamycin is another alternative drug for treatment of genital C.trachomatis infection. Despite it being safe in pregnancy, clindamycin is not used widely due to its cost (Miller 2000).

Other antibiotics such as doxycycline, levofloxacin, ofloxacin, and erythromycin estolate are used for the treatment of genital C.trachomatis outside of pregnancy. These drugs are contraindicated in pregnancy and lactation (Workowski 2010).

Azithromycin is believed to be the superior agent in comparison to other antibiotics for treatment of chlamydial infection but new research has emerged suggesting that there is a higher failure rate with azithromycin treatment of chlamydial infection than previously believed (Schwebke 2011). One of the explanations for this recent finding is a higher sensitivity of NAAT in comparison to that previously used in the tissue culture as a test of cure (Handsfield 2011), although it does not explain the similar cure rates reported after doxycycline treatment with both of these tests. Another explanation for treatment failure is heterotopic resistance with high Chlamydia loads which leads to treatment failures (Horner 2006). Re‐infection is also a cause of treatment failure (Horner 2006).

Cure rates of C.trachomatis in women who are pregnant are lower than in non‐pregnant women. The reasons behind this is a generally higher failure rate of treatment with amoxicillin, which has been traditionally used for treatment of C.trachomatis infection during pregnancy. A test of cure has always been recommended for all pregnant women and is performed no earlier than three weeks after treatment is initiated (Workowski 2010).

The previous Cochrane review on interventions for treating genital C.trachomatis infection in pregnancy found that amoxicillin was as effective as erythromycin (odds ratio (OR) 0.54, 95% confidence interval (CI) 0.28 to 1.02) (Brocklehurst 1998). Amoxycillin was found to be better tolerated than erythromycin (OR 0.16, 95% CI 0.09 to 0.30). Clindamycin and azithromycin were reported to be effective, however, the numbers of women included in trials were small (Brocklehurst 1998). New studies have been published in this area, therefore, it is important to update this review, which was done under new authorship.

How the intervention might work

Irradicating genital chlamydial infection during pregnancy with antibacterial drugs may lead to the following:

treatment of symptoms and sequelae of genital chlamydial infection such as discharge, cervicitis, pelvic inflammatory disease, tubal disease and infertility;
a decrease in perinatal complications such as preterm labour and early pregnancy loss, preterm rupture of membranes;
a decrease in transmission of the infection to the fetus or newborn and, therefore, prevention of intrauterine infection, neonatal conjunctivitis and pneumonia during pregnancy;
prevention of postpartum infection such as endometritis.

Why it is important to do this review

It is important to assess the different interventions for treating genital C.trachomatis in order to establish whether effective treatment of this infection improves perinatal outcomes and decreases maternal complications. This new review updates and replaces an earlier Cochrane review on this topic (Brocklehurst 1998).

Objectives

To establish the most efficacious and best‐tolerated therapy for treatment of genital chlamydial infection in preventing maternal infection and adverse neonatal outcomes.

Methods

Criteria for considering studies for this review

Types of studies

We included randomised controlled trials. Cluster‐randomised trials will be eligible for inclusion in this review in the future updates if identified. Quasi‐randomised trials and trials using cross‐over design were not eligible for inclusion. We included studies published in abstract form.

Types of participants

Pregnant women with a confirmed C.trachomatis infection.

Types of interventions

Any antibiotic versus no treatment or placebo for genital C.trachomatiss infection in pregnancy
One antibiotic versus another antibiotic
Different antibacterial regimens

Types of outcome measures

Primary outcomes

Microbiological cure ‐ negative Chlamydia test at least three weeks after treatment of the mother

Secondary outcomes

A. Maternal

Repeated infection
Preterm labour
Preterm birth
Preterm rupture of membranes
Chorioamnionitis
Postpartum endometritis
Sepsis
Prolonged hospital stay of the mother
Side effects of treatment
Maternal satisfaction with treatment

B. Fetal/neonatal

Perinatal mortality
Neonatal conjunctivitis
Neonatal pneumonia
Fetal anomalies
Low birthweight
Apgar score less than seven at five minutes

C. Cost

Cost of treatment

Search methods for identification of studies

The methods section of this review is based on a standard template used by the Cochrane Pregnancy and Childbirth Group.

Electronic searches

We searched the Cochrane Pregnancy and Childbirth Group’s Trials Register by contacting their Information Specialist (26 June 2017).

The Register is a database containing over 23,000 reports of controlled trials in the field of pregnancy and childbirth. For full search methods used to populate the Pregnancy and Childbirth Group’s Trials Register including the detailed search strategies for CENTRAL, MEDLINE, Embase and CINAHL, the list of handsearched journals and conference proceedings, and the list of journals reviewed via the current awareness service, please follow this link to the editorial information about the Cochrane Pregnancy and Childbirth Group in the Cochrane Library and select the ‘Specialized Register ’ section from the options on the left side of the screen.

Briefly, the Cochrane Pregnancy and Childbirth’s Trials Register is maintained by their Information Specialist and contains trials identified from:

monthly searches of the Cochrane Central Register of Controlled Trials (CENTRAL);
weekly searches of MEDLINE (Ovid);
weekly searches of Embase (Ovid);
monthly searches of CINAHL (EBSCO);
handsearches of 30 journals and the proceedings of major conferences;
weekly current awareness alerts for a further 44 journals plus monthly BioMed Central email alerts.

Search results are screened by two people and the full text of all relevant trial reports identified through the searching activities described above is reviewed. Based on the intervention described, each trial report is assigned a number that corresponds to a specific Pregnancy and Childbirth review topic (or topics), and is then added to the Register. The Information Specialist searches the Register for each review using this topic number rather than keywords. This results in a more specific search set that has been fully accounted for in the relevant review sections (Included studies; Excluded studies; Ongoing studies)

In addition, we searched ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform (ICTRP) (26 June 2017) for unpublished, planned and ongoing trial reports. The search terms we used are given in Appendix 1.

Searching other resources

We searched the reference lists of retrieved studies.

We did not apply any language or date restrictions.

Data collection and analysis

The methods section of this review is based on a standard template used by the Cochrane Pregnancy and Childbirth Group.

Selection of studies

Two review authors independently assessed all the potential studies identified as a result of the search strategy for inclusion. Two review authors assessed the quality and extracted the data using the agreed form. Discrepancies were resolved through discussion with a third review author when needed. We entered data into Review Manager software and checked for accuracy. When information regarding any of the above was unclear, we attempted to contact authors of the original reports to provide further details.

Studies published only in abstract form were included if they otherwise satisfied inclusion criteria. The authors of such studies were contacted if any additional information was required.

Data extraction and management

We designed a form to extract data. For eligible studies, review authors extracted the data using the agreed form. We resolved discrepancies through discussion or, if required, we consulted a third assessor. We entered data into Review Manager software (RevMan 2014), and checked for accuracy.

When information regarding any of the above is unclear, we attempted to contact authors of the original reports to provide further details.

Assessment of risk of bias in included studies

Review authors independently assessed risk of bias for each study using the criteria outlined in the Cochrane Handbook for Systematic Reviews of Interventions(Higgins 2011). We resolved any disagreement by discussion or by involving a third assessor.

(1) Random sequence generation (checking for possible selection bias)

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

We assessed the method as:

low risk of bias (any truly random process, e.g. random number table; computer random number generator);
high risk of bias (any non‐random process, e.g. odd or even date of birth; hospital or clinic record number);
unclear risk of bias.

(2) Allocation concealment (checking for possible selection bias)

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

We assessed the methods as:

low risk of bias (e.g. telephone or central randomisation; consecutively numbered sealed opaque envelopes);
high risk of bias (open random allocation; unsealed or non‐opaque envelopes, alternation; date of birth);
unclear risk of bias.

(3.1) Blinding of participants and personnel (checking for possible performance bias)

We described for each included study the methods used, if any, to blind study participants and personnel from knowledge of which intervention a participant received. We considered that studies were at low risk of bias if they were blinded, or if we judged that the lack of blinding would be unlikely to affect results. We assessed blinding separately for different outcomes or classes of outcomes.

We assessed the methods as:

low, high or unclear risk of bias for participants;
low, high or unclear risk of bias for personnel.

(3.2) Blinding of outcome assessment (checking for possible detection bias)

We described for each included study the methods used, if any, to blind outcome assessors from knowledge of which intervention a participant received. We assessed blinding separately for different outcomes or classes of outcomes.

We assessed methods used to blind outcome assessment as:

low, high or unclear risk of bias.

(4) Incomplete outcome data (checking for possible attrition bias due to the amount, nature and handling of incomplete outcome data)

We described for each included study, and for each outcome or class of outcomes, the completeness of data including attrition and exclusions from the analysis. We stated whether attrition and exclusions were reported and the numbers included in the analysis at each stage (compared with the total randomised participants), reasons for attrition or exclusion where reported, and whether missing data were balanced across groups or were related to outcomes. Where sufficient information was reported, or could be supplied by the trial authors, we re‐included missing data in the analyses which we undertook.

We assessed methods as:

low risk of bias (e.g. no missing outcome data; missing outcome data balanced across groups);
high risk of bias (e.g. numbers or reasons for missing data imbalanced across groups; ‘as treated’ analysis done with substantial departure of intervention received from that assigned at randomisation);
unclear risk of bias.

A cut‐off point of 20% was used to assess the level of missing data as adequate for different outcomes.

(5) Selective reporting (checking for reporting bias)

We described for each included study how we investigated the possibility of selective outcome reporting bias and what we found.

We assessed the methods as:

low risk of bias (where it is clear that all of the study’s pre‐specified outcomes and all expected outcomes of interest to the review have been reported);
high risk of bias (where not all the study’s pre‐specified outcomes have been reported; one or more reported primary outcomes were not pre‐specified; 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 risk of bias.

(6) Other bias (checking for bias due to problems not covered by (1) to (5) above)

We described for each included study any important concerns we have about other possible sources of bias.

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

low risk of other bias;
high risk of other bias;
unclear whether there is risk of other bias.

(7) Overall risk of bias

We made explicit judgements about whether studies were at high risk of bias, according to the criteria given in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011). 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 explored the impact of the level of bias through undertaking sensitivity analyses ‐ seeSensitivity analysis.

Assessment of the quality of the evidence using the GRADE approach

For this update , we assessed the quality of the evidence for all comparisons using the GRADE approach as outlined in the GRADE handbook in order to assess the quality of the body of evidence relating to the main outcome of microbiological cure.

We used GRADEpro GDT to import data from Review Manager 5.3 (RevMan 2014) to create 'Summary of findings' tables. A summary of the intervention effect and a measure of quality for each of the outcomes was produced using the GRADE approach. The GRADE approach uses five considerations (study limitations, consistency of effect, imprecision, indirectness and publication bias) to assess the quality of the body of evidence for each outcome. The evidence can be downgraded from 'high quality' by one level for serious (or by two levels for very serious) limitations, depending on assessments for risk of bias, indirectness of evidence, serious inconsistency, imprecision of effect estimates or potential publication bias.

Measures of treatment effect

Dichotomous data

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

Continuous data

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

Unit of analysis issues

Cluster‐randomised trials

We did not identify any cluster‐randomised trials for inclusion in this version of the review. If we identify any cluster‐randomised trials for inclusion in future updates, we will include them in our analyses along with individually‐randomised trials. We will adjust their standard errors using the methods described in the Cochrane Handbook for Systematic Reviews of Interventions using an estimate of the intra‐cluster correlation co‐efficient (ICC) derived from the trial (if possible), from a similar trial or from a study of a similar population. If we use ICCs from other sources, we will report this and conduct sensitivity analyses to investigate the effect of variation in the ICC. If we identify both cluster‐randomised trials and individually‐randomised trials, we will synthesise the relevant information. We will consider it reasonable to combine the results from both if there is little heterogeneity between the studies and the interaction between the effect of intervention and the choice of randomisation unit is considered to be unlikely.

We will acknowledged heterogeneity in the randomisation unit and perform a subgroup analysis to investigate the effects of the randomisation unit.

Cross‐over trials

This study design is not eligible for inclusion in this review.

Other unit of analysis issues

We identified the trials with more than two treatment groups and included each pair‐wise comparison separately, but with shared intervention groups divided out approximately evenly among the comparisons. For dichotomous outcomes, both the number of events and the total number of patients were divided up. For continuous outcomes, only the total number of participants were divided up and the means and standard deviations left unchanged (Cochrane Handbook for Systematic Reviews of Interventions 16.5.4).

Dealing with missing data

For included studies, we noted levels of attrition. We planned to explore the impact of including studies with high levels of missing data in the overall assessment of treatment effect by using sensitivity analysis (see Sensitivity analysis).

For all outcomes, we carried out analyses, as far as possible, on an intention‐to‐treat basis, i.e. we attempted to include all participants randomised to each group in the analyses, and all participants were analysed in the group to which they were allocated, regardless of whether or not they received the allocated intervention. The denominator for each outcome in each trial was the number randomised minus any participants whose outcomes were known to be missing.

We would have excluded studies with more than 20% missing data.

Assessment of heterogeneity

We assessed statistical heterogeneity in each meta‐analysis using the T², I² and Chi² statistics. We regarded heterogeneity as substantial if the I² was greater than 30% and either the T² was greater than zero, or there was a low P value (less than 0.10) in the Chi² test for heterogeneity.

Assessment of reporting biases

In future updates of this review, if there are 10 or more studies in the meta‐analysis, we will investigate reporting biases (such as publication bias) using funnel plots and will assess funnel plot asymmetry visually. If asymmetry is suggested by a visual assessment, we will perform exploratory analyses to investigate it.

Data synthesis

We carried out statistical analysis using the Review Manager software (RevMan 2014). We 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 used random‐effects meta‐analysis to produce an overall summary, if an average treatment effect across trials was considered clinically meaningful. The random‐effects summary was treated as the average range of possible treatment effects and we discussed the clinical implications of treatment effects differing between trials. If the average treatment effect was not clinically meaningful, we did not combine trials.

Where we used random‐effects analyses, the results are presented as the average treatment effect with 95% confidence intervals, and the estimates of T² and I².

Subgroup analysis and investigation of heterogeneity

We did not carry out ant of the planned subgroup analyses as the outcomes only had a few included trials. In future updates if we identify substantial heterogeneity, we will investigate it using subgroup analyses and sensitivity analyses. We will consider whether an overall summary is meaningful, and if it is, use random‐effects analysis to produce it.

We would consider carrying out the following subgroup analyses.

Women with a first episode versus women with recurrent (previously treated in pregnancy) genital C.trachomatis infection
Women in the first half (before 20 weeks) versus women in the second half (including 20 weeks and after 20 weeks) of pregnancy

The following outcome would be used in subgroup analysis.

Microbiological cure negative Chlamydia test after treatment for the mother

We would have assessed subgroup differences by interaction tests available within RevMan (RevMan 2014). We would have reported the results of subgroup analyses quoting the Chi² statistic and P value, and the interaction test I² value.

Sensitivity analysis

Sensitivity analyses were not performed as there were no aspects of the review that may have affected the results, for example, the risk of bias associated with the quality of some of the included trials. We would have undertaken analysis of the primary outcome separately for trials with low risk of bias and high and unknown risk of bias (allocation concealment) if needed. Sensitivity analysis would have been carried out to explore the effects of random‐effects analyses for outcomes with statistical heterogeneity. We would also have carried out sensitivity analysis to investigate the effect of the randomisation unit if we had included cluster‐randomised controlled trials along with the individually‐randomised trials.

Results

Description of studies

Results of the search

The search of the Cochrane Pregnancy and Childbirth Group's Trials Register retrieved 23 reports of 20 trials and we retrieved no other studies from other sources (see: Figure 1). We included 15 studies, excluded four, and one is ongoing (Okunola 2013).

Included studies

We included 15 studies into the meta‐analysis with a total of 1754 women. Meta‐analyses were mostly based on fewer numbers of studies.

Methods

All the trials were randomised control trials of pregnant women with confirmed Chlamydia trachomatis (C.trachomatis) infection.

Populations and settings

All of the included studies were undertaken in North America (14 in USA and one in Canada). One study took place in 1982, and the rest took place in the nineties and early 2000s.

Interventions and comparisons

Two studies compared erythromycin and placebo (Alger 1991; Martin 1997). One study compared clindamycin and placebo (Alger 1991). One study compared amoxicillin versus placebo (Bell 1982). Two studies compared azithromycin and amoxicillin (Jacobson 2001; Kacmar 2001). Four studies compared amoxicillin and erythromycin (Alary 1994; Magat 1993; Silverman 1994; Turrentine 1995). Six studies compared erythromycin and azithromycin (Adair 1998; Bush 1994; Edwards 1996; Gunter 1996; Rosenn 1995; Wehbeh 1998). Two studies compared clindamycin and erythromycin (Alger 1991; Turrentine 1995). One study compared amoxicillin and clindamycin (Turrentine 1995).

Funding sources

Adair 1998, Edwards 1996, and Turrentine 1995 had drugs donated by a pharmaceutical company at no cost. Alger 1991 was funded by a grant from the Upjohn company.

Alary 1994 was funded by a grant from the National Health Research and Development Program. Kacmar 2001 was funded by a NIH grant. Martin 1997 was funded by a National Institute of Child Health and Human Development grant. Bell 1982 was supported by a US Public Health Service grant.

Wehbeh 1998 was funded by local departmental funds.

Bush 1994, Gunter 1996, Jacobson 2001, Magat 1993, Rosenn 1995, and Silverman 1994 did not disclose any funding sources.

Trial authors' declarations of interest

Declarations of interest were not mentioned in any of the included studies.

Excluded studies

Reasons for exclusion are as follows.

El‐Shourbagy 2011 ‐ this study examines the rate of pre‐eclampsia in groups of treated and non‐treated Chlamydia pneumoniae infections in pregnancy.
McGregor 1990 ‐ this study included pregnant women with various genital tract infections and not only Chlamydia trachomatis. The data for Chlamydia trachomatis infection were not presented separately.
Nadafi 2005 ‐ this study included women with positive and negative Chlamydia test, it was a cohort study, sequence generation was not clear. The data for women with positive and negative Chlamydia test are presented together.
Zulkarneev 1998 ‐ this study was not a randomised controlled trial.

Risk of bias in included studies

SeeFigure 2 and Figure 3.

'Risk of bias' graph: review authors' judgements about each risk of bias item presented as percentages across all included studies.

'Risk of bias' summary: review authors' judgements about each risk of bias item for each included study.

Allocation

Eleven studies had low risk of selection bias, e.g. three studies used number of blocks for allocation (Adair 1998; Alary 1994; Rosenn 1995), four studies used computer‐generated randomisation for allocation (Bush 1994; Jacobson 2001; Martin 1997; Turrentine 1995), four studies used random number tables (Edwards 1996; Kacmar 2001; Magat 1993; Silverman 1994). Four studies had unclear risk of selection bias, e.g. allocation method was not described (Alger 1991; Bell 1982; Gunter 1996; Wehbeh 1998).

Nine studies had a low risk of bias for allocation sequence. Six used sealed opaque envelopes (Adair 1998; Bush 1994; Jacobson 2001, Kacmar 2001; Rosenn 1995; Silverman 1994). One study used identical treatment packs (Alary 1994). In two trials the medications were dispensed by the pharmacy to prevent the healthcare practitioners knowing which medication and which dose were allocated (Magat 1993; Turrentine 1995). There was an unclear risk in six studies as allocation concealment was not described (Alger 1991; Bell 1982; Edwards 1996; Gunter 1996; Martin 1997; Wehbeh 1998).

Blinding

Performance bias

Blinding of participants and personnel was performed four studies (Alary 1994; Alger 1991; Martin 1997; Turrentine 1995).

Five studies did not implement blinding of participants or personnel and were assessed as high risk (Adair 1998; Edwards 1996; Jacobson 2001; Magat 1993; Wehbeh 1998).

Six studies did not describe performance blinding (Bell 1982; Bush 1994; Gunter 1996; Kacmar 2001; Rosenn 1995; Silverman 1994).

Assessment bias

Blinding of outcome assessment was unclear in 13 studies (Adair 1998; Alger 1991; Bell 1982; Bush 1994; Edwards 1996; Gunter 1996; Jacobson 2001; Kacmar 2001; Magat 1993; Martin 1997; Rosenn 1995; Silverman 1994; Wehbeh 1998).

Assessment bias was assessed as low risk in two studies were staff taking cultures were blinded to treatment group (Alary 1994; Turrentine 1995).

Incomplete outcome data

No studies had significant attrition bias. All losses to follow‐up were described. One study (Bell 1982) had high attrition for the final outcome reporting data for only 71% of participants. Five studies are at unclear risk of attrition bias due to insufficient information given in the study report (Gunter 1996), and some unexplained loss to follow‐up (Jacobson 2001; Kacmar 2001; Martin 1997; Silverman 1994).

Selective reporting

One study was published only in abstract form and states that it is an ongoing trial but no further information has been published (Gunter 1996). The remaining 14 studies were rated as being at low risk of reporting bias.

Other potential sources of bias

Two studies had unexplained different mean gestational ages in women in the two treatment arms (Edwards 1996; Magat 1993). The remaining 13 studies were assessed as being at a low risk of other bias.

Effects of interventions

See: Table 1; Table 2; Table 3; Table 4; Table 5; Table 6; Table 7; Table 8

Summary of findings for the main comparison. Erythromycin compared to placebo for treating genital Chlamydia trachomatis infection in pregnancy.

*Erythromycin compared to placebo for treating genital Chlamydia trachomatis* infection in pregnancy**
Patient or population: Pregnant women with a confirmed Chlamydia trachomatis infection  Setting: Obstetric Clinics, USA  Intervention: Erythromycin  Comparison: Placebo
Outcomes	*Anticipated absolute effects^ (95% CI)**		Relative effect  (95% CI)	№ of participants  (studies)	Quality of the evidence  (GRADE)	Comments
	Risk with placebo	Risk with Erythromycin
Microbiological cure	Study population		Average RR 2.64  (1.60 to 4.38)	495  (2 RCTs)	⊕⊕⊕⊝  MODERATE ^{1 2}
	344 per 1000	908 per 1000  (550 to 1000)
*The risk in the intervention group (and its 95% CI) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).    CI: Confidence interval; RR: Risk ratio
GRADE Working Group grades of evidence   High quality: We are very confident that the true effect lies close to that of the estimate of the effect  Moderate quality: We are moderately confident in the effect estimate: The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different  Low quality: Our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect  Very low quality: We have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect

*Clindamycin compared to placebo for treating genital Chlamydia trachomatis* infection in pregnancy**
Patient or population: Pregnant women with a confirmed Chlamydia trachomatis infection  Setting: Obstetric Clinic, USA  Intervention: Clindamycin  Comparison: Placebo
Outcomes	*Anticipated absolute effects^ (95% CI)**		Relative effect  (95% CI)	№ of participants  (studies)	Quality of the evidence  (GRADE)	Comments
	Risk with placebo	Risk with Clindamycin
Microbiological cure	Study population		RR 4.08  (2.35 to 7.08)	85  (1 RCT)	⊕⊕⊝⊝  LOW ^{1 2}
	227 per 1000	927 per 1000  (534 to 1000)
*The risk in the intervention group (and its 95% CI) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).    CI: Confidence interval; RR: Risk ratio
GRADE Working Group grades of evidence   High quality: We are very confident that the true effect lies close to that of the estimate of the effect  Moderate quality: We are moderately confident in the effect estimate: The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different  Low quality: Our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect  Very low quality: We have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect

*Amoxicillin compared to placebo for treating genital Chlamydia trachomatis* infection in pregnancy**
Patient or population: Pregnant women with a confirmed Chlamydia trachomatis infection  Setting: USA  Intervention: Amoxicillin  Comparison: Placebo
Outcomes	*Anticipated absolute effects^ (95% CI)**		Relative effect  (95% CI)	№ of participants  (studies)	Quality of the evidence  (GRADE)	Comments
	Risk with placebo	Risk with Amoxicillin
Microbiological cure	Study population		RR 2.00  (0.59 to 6.79)	15  (1 RCT)	⊕⊝⊝⊝  VERY LOW ^{1 2}
	333 per 1000	667 per 1000  (197 to 1000)
*The risk in the intervention group (and its 95% CI) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).    CI: Confidence interval; RR: Risk ratio
GRADE Working Group grades of evidence   High quality: We are very confident that the true effect lies close to that of the estimate of the effect  Moderate quality: We are moderately confident in the effect estimate: The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different  Low quality: Our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect  Very low quality: We have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect

*Amoxicillin compared to azithromycin for treating genital Chlamydia trachomatis* infection in pregnancy**
Patient or population: Pregnant women with a confirmed Chlamydia trachomatis infection  Setting: Prenatal clinics, USA  Intervention: Amoxicillin  Comparison: Azithromycin
Outcomes	*Anticipated absolute effects^ (95% CI)**		Relative effect  (95% CI)	№ of participants  (studies)	Quality of the evidence  (GRADE)	Comments
	Risk with azithromycin	Risk with Amoxicillin
Microbiological cure	Study population		RR 0.89  (0.71 to 1.12)	144  (2 RCTs)	⊕⊝⊝⊝  VERY LOW ^{1 2}
	716 per 1000	637 per 1000  (509 to 802)
*The risk in the intervention group (and its 95% CI) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).    CI: Confidence interval; RR: Risk ratio
GRADE Working Group grades of evidence   High quality: We are very confident that the true effect lies close to that of the estimate of the effect  Moderate quality: We are moderately confident in the effect estimate: The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different  Low quality: Our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect  Very low quality: We have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect

*Amoxicillin compared to erythromycin for treating genital Chlamydia trachomatis* infection in pregnancy**
Patient or population: Pregnant women with a confirmed Chlamydia trachomatis infection  Setting: Obstetric centre or prenatal clinics in Canada, USA  Intervention: Amoxicillin  Comparison: Erythromycin
Outcomes	*Anticipated absolute effects^ (95% CI)**		Relative effect  (95% CI)	№ of participants  (studies)	Quality of the evidence  (GRADE)	Comments
	Risk with erythromycin	Risk with Amoxicillin
Microbiological cure	Study population		RR 0.97  (0.93 to 1.01)	466  (4 RCTs)	⊕⊕⊕⊕  HIGH	One study contributing to 24% of weight had some design limitation. (not downgraded)
	954 per 1000	925 per 1000  (887 to 963)
*The risk in the intervention group (and its 95% CI) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).    CI: Confidence interval; RR: Risk ratio
GRADE Working Group grades of evidence   High quality: We are very confident that the true effect lies close to that of the estimate of the effect  Moderate quality: We are moderately confident in the effect estimate: The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different  Low quality: Our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect  Very low quality: We have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect

*Azithromycin compared to erythromycin for treating genital Chlamydia trachomatis* infection in pregnancy**
Patient or population: Pregnant women with a confirmed Chlamydia trachomatis infection  Setting: Prenatal clinics, and university medical centres, USA  Intervention: Azithromycin  Comparison: erythromycin
Outcomes	*Anticipated absolute effects^ (95% CI)**		Relative effect  (95% CI)	№ of participants  (studies)	Quality of the evidence  (GRADE)	Comments
	Risk with erythromycin	Risk with Azithromycin
Microbiological cure	Study population		Average RR 1.11  (1.00 to 1.23)	374  (6 RCTs)	⊕⊕⊕⊝  MODERATE ^{1 2}
	825 per 1000	916 per 1000  (825 to 1000)
*The risk in the intervention group (and its 95% CI) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).    CI: Confidence interval; RR: Risk ratio
GRADE Working Group grades of evidence   High quality: We are very confident that the true effect lies close to that of the estimate of the effect  Moderate quality: We are moderately confident in the effect estimate: The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different  Low quality: Our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect  Very low quality: We have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect

*Clindamycin compared to erythromycin for treating genital Chlamydia trachomatis* infection in pregnancy**
Patient or population: Pregnant women with a confirmed Chlamydia trachomatis infection  Setting: Prenatal clinics, USA  Intervention: Clindamycin  Comparison: Erythromycin
Outcomes	*Anticipated absolute effects^ (95% CI)**		Relative effect  (95% CI)	№ of participants  (studies)	Quality of the evidence  (GRADE)	Comments
	Risk with erythromycin	Risk with Clindamycin
Microbiological cure	Study population		RR 1.06  (0.97 to 1.15)	173  (2 RCTs)	⊕⊕⊝⊝  LOW ^{1 2}
	905 per 1000	959 per 1000  (878 to 1000)
*The risk in the intervention group (and its 95% CI) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).    CI: Confidence interval; RR: Risk ratio
GRADE Working Group grades of evidence   High quality: We are very confident that the true effect lies close to that of the estimate of the effect  Moderate quality: We are moderately confident in the effect estimate: The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different  Low quality: Our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect  Very low quality: We have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect

*Amoxicillin compared to clindamycin for treating genital Chlamydia trachomatis* infection in pregnancy**
Patient or population: Pregnant women with a confirmed Chlamydia trachomatis infection  Setting: Prenatal clinic, USA  Intervention: Amoxicillin  Comparison: Clindamycin
Outcomes	*Anticipated absolute effects^ (95% CI)**		Relative effect  (95% CI)	№ of participants  (studies)	Quality of the evidence  (GRADE)	Comments
	Risk with clindamycin	Risk with Amoxicillin
Microbiological cure	Study population		RR 0.96  (0.89 to 1.04)	101  (1 RCT)	⊕⊕⊕⊝  MODERATE ¹
	979 per 1000	940 per 1000  (871 to 1000)
*The risk in the intervention group (and its 95% CI) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).    CI: Confidence interval; RR: Risk ratio
GRADE Working Group grades of evidence   High quality: We are very confident that the true effect lies close to that of the estimate of the effect  Moderate quality: We are moderately confident in the effect estimate: The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different  Low quality: Our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect  Very low quality: We have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Microbiological cure	2	495	Risk Ratio (M‐H, Random, 95% CI)	2.64 [1.60, 4.38]
2 Preterm birth	1	405	Risk Ratio (M‐H, Fixed, 95% CI)	0.90 [0.56, 1.46]
3 Preterm rupture of membranes	1	389	Risk Ratio (M‐H, Fixed, 95% CI)	0.83 [0.48, 1.43]
4 Side effects of treatment	2	495	Risk Ratio (M‐H, Random, 95% CI)	2.93 [0.36, 23.76]
5 Perinatal mortality	1	405	Risk Ratio (M‐H, Fixed, 95% CI)	3.01 [0.32, 28.74]
6 Low birthweight	1	400	Risk Ratio (M‐H, Fixed, 95% CI)	0.77 [0.42, 1.40]

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Microbiological cure	1	85	Risk Ratio (M‐H, Fixed, 95% CI)	4.08 [2.35, 7.08]
2 Side effects of treatment	1	85	Risk Ratio (M‐H, Fixed, 95% CI)	5.37 [0.65, 44.01]

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Microbiological cure	2	144	Risk Ratio (M‐H, Fixed, 95% CI)	0.89 [0.71, 1.12]
2 Repeated infection	1	34	Risk Ratio (M‐H, Fixed, 95% CI)	0.42 [0.02, 9.55]
3 Preterm birth	1	90	Risk Ratio (M‐H, Fixed, 95% CI)	1.17 [0.43, 3.20]
4 Side effects of treatment	1	36	Risk Ratio (M‐H, Fixed, 95% CI)	0.56 [0.24, 1.31]

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Microbiological cure	4	466	Risk Ratio (M‐H, Fixed, 95% CI)	0.97 [0.93, 1.01]
2 Side effects of treatment	4	513	Risk Ratio (M‐H, Fixed, 95% CI)	0.31 [0.21, 0.46]

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Microbiological cure	6	374	Risk Ratio (M‐H, Random, 95% CI)	1.11 [1.00, 1.23]
2 Repeated infection	1	85	Risk Ratio (M‐H, Fixed, 95% CI)	1.37 [0.32, 5.73]
3 Preterm birth	1	126	Risk Ratio (M‐H, Fixed, 95% CI)	0.77 [0.29, 2.10]
4 Preterm rupture of membranes	1	126	Risk Ratio (M‐H, Fixed, 95% CI)	0.62 [0.15, 2.48]
5 Side effects of treatment	6	374	Risk Ratio (M‐H, Fixed, 95% CI)	0.24 [0.17, 0.34]

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Microbiological cure	2	173	Risk Ratio (M‐H, Fixed, 95% CI)	1.06 [0.97, 1.15]
2 Side effects of treatment	2	183	Risk Ratio (M‐H, Fixed, 95% CI)	0.44 [0.22, 0.87]

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Microbiological cure	1	101	Risk Ratio (M‐H, Fixed, 95% CI)	0.96 [0.89, 1.04]
2 Side effects of treatment	1	107	Risk Ratio (M‐H, Fixed, 95% CI)	0.57 [0.14, 2.26]

Methods	Randomised controlled trial.
Participants	106 pregnant women screened positive by a direct DNA probe for Chlamydia trachomatis were enrolled. Exclusion criteria included hypersensitivity to erythromycin or azithromycin, lack of desire to participate in the study, or gestational age at most 14 weeks. 85 women entered and completed the entire trial protocol. 42 were assigned to azithromycin and 43 were assigned to erythromycin.
Interventions	Azithromycin 1 g oral slurry in a single dose or erythromycin base 500 mg orally 4 times daily for 7 days.
Outcomes	Cure rate, repeated infection, side effects (nausea and vomiting).
Notes	In the azithromycin group, 9 were lost to follow‐up, 2 were not pregnant, 1 was treated off protocol.  In the erythromycin group, 7 were lost to follow‐up, 2 were not pregnant, 1 was treated off protocol.  74.4% in the erythromycin group and 50% in the azithromycin group completed the protocol as prescribed within the 3‐week period. This high rate of prolonged, unconfirmed test of cure could have resulted in higher positive tests of cure or possibly higher re‐infection rates in the azithromycin group.  Compliance in the azithromycin group was 97.6% and in the erythromycin group it was 53.5%.  Patients with positive Chlamydia assays at the test of cure were treated with the alternative agent to the originally assigned agent.  Sample size estimates suggested the need to enrol 120 patients. Performed at Bowman Gray School of Medicine of Wake Forest University, North Carolina, USA. Sources of trial funding: The drugs used in this study were supplied without charge by Pfizer, Incorporated, New York, New York. Declarations of interest: Not reported. Trial dates: 1995 ‐ 1997.
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Assignment to treatment was made by random numbers in blocks of 20 by the program Rancode‐Plus 3.1.1.
Allocation concealment (selection bias)	Low risk	Allocation cards were placed in a sealed opaque envelope.
Blinding of participants and personnel (performance bias)   All outcomes	High risk	No attempt was made to blind the investigators to treatment allocations after enrolment.
Blinding of outcome assessment (detection bias)   All outcomes	Unclear risk	Not described.
Incomplete outcome data (attrition bias)   All outcomes	Low risk	85 (80.2%) women completed the study. The number lost to follow‐up was similar in both the groups.
Selective reporting (reporting bias)	Low risk	No selective reporting noted.
Other bias	Low risk	The study appears to be free of other sources of bias.

Study	Reason for exclusion
El‐Shourbagy 2011	This study examines the rate of pre‐eclampsia in groups of treated and non‐treated Chlamydia pneumoniae infections in pregnancy.
McGregor 1990	This study included pregnant women with various genital tract infections and not only C.trachomatis. The data for C.trachomatis infection were not presented separately.
Nadafi 2005	Not all participants of this trial had C.trachomatis infection, therefore, the study was excluded.
Zulkarneev 1998	This study was not a randomised controlled trial.

Trial name or title	Treatment of antenatal Chlamydia infection.
Methods	Randomised controlled trial. Open label.
Participants	Pregnant women at less than 36 weeks' gestation with positive C.trachomatis test on endocervical swab with rapid kit. Exlcuded with history of antibiotics in the last 2 weeks or low lying placenta, history of reaction to any of the drugs. Plan to recruit 200 participants.
Interventions	Group 1 ‐ amoxicillin 500 mg orally 3 times a day for a week. Group 2 ‐ erythromycin 500 mg 4 times a day for a week. Partners were treated with doxycycline for a week.
Outcomes	Completiion of course treatment. Microbiological cure. Side effects (nausea, diarrhoea, vomiting, loss of appetite).
Starting date	October 2013.
Contact information	Obafemi Awolowo University Teaching Hospital.
Notes	Clinical Trial identifier NCT01946256.

PERMALINK

Interventions for treating genital Chlamydia trachomatis infection in pregnancy

Catherine Cluver

Natalia Novikova

David OA Eriksson

Kevin Bengtsson

Göran K Lingman

Abstract

Background

Objectives

Search methods

Selection criteria

Data collection and analysis

Main results

Authors' conclusions

Plain language summary

Summary of findings

Background

Description of the condition

Description of the intervention

How the intervention might work

Why it is important to do this review

Objectives

Methods

Criteria for considering studies for this review

Types of studies

Types of participants

Types of interventions

Types of outcome measures

Primary outcomes

Secondary outcomes

A. Maternal

B. Fetal/neonatal

C. Cost

Search methods for identification of studies

Electronic searches

Searching other resources

Data collection and analysis

Selection of studies

Data extraction and management

Assessment of risk of bias in included studies

(1) Random sequence generation (checking for possible selection bias)

(2) Allocation concealment (checking for possible selection bias)

(3.1) Blinding of participants and personnel (checking for possible performance bias)

(3.2) Blinding of outcome assessment (checking for possible detection bias)

(4) Incomplete outcome data (checking for possible attrition bias due to the amount, nature and handling of incomplete outcome data)

(5) Selective reporting (checking for reporting bias)

(6) Other bias (checking for bias due to problems not covered by (1) to (5) above)

(7) Overall risk of bias

Assessment of the quality of the evidence using the GRADE approach

Measures of treatment effect

Dichotomous data

Continuous data

Unit of analysis issues

Cluster‐randomised trials

Cross‐over trials

Other unit of analysis issues

Dealing with missing data

Assessment of heterogeneity

Assessment of reporting biases

Data synthesis

Subgroup analysis and investigation of heterogeneity

Sensitivity analysis

Results

Description of studies

Results of the search

1.

Included studies

Methods

Populations and settings

Interventions and comparisons

Funding sources

Trial authors' declarations of interest

Excluded studies

Risk of bias in included studies

2.

3.

Allocation

Blinding

Performance bias