Effectiveness of Vaginal Magnesium Sulfate on Pain and Labor Duration: A systematic review and meta-analysis

Summary

This systematic review and meta-analysis aimed to evaluate the effectiveness of vaginal magnesium sulfate (MgSO₄) administration during labour. A comprehensive search was conducted across six databases up to 30 July 2024, and updated on 13 January 2025, with no restrictions on time, language, or geographical region. The risk of bias was assessed using the RoB 2 tool, and the certainty of evidence was evaluated using GRADEpro. A total of seven randomised controlled trials were included. The meta-analysis demonstrated that topical magnesium sulfate significantly increased cervical dilatation by 2.27 cm (95% confidence interval [CI]: 1.98 to 2.56; P <0.00001) and cervical effacement by 15.3% (95% CI: 7.79 to 22.82; P <0.0001) two hours after administration, compared to control groups. Furthermore, it shortened the active phase of labour by 1.63 hours (95% CI: -2.15 to -1.11; P <0.00001) and reduced reported pain levels. These findings suggest that vaginal magnesium sulfate may be a promising and easily administered intervention, warranting further investigation in clinical practice.

1. Introduction

Childbirth is a natural physiological process that often evokes feelings of anticipation and excitement in expectant mothers. It can have a significant impact on women's lives and is closely linked to their overall quality of life.^1,2 As such, one of the principal objectives of safe delivery is to reduce labour-associated pain, stress, and duration.¹

Various pharmacological and non-pharmacological methods are available to facilitate cervical ripening and prepare for childbirth. Among the commonly used pharmacological agents are nitric oxide-releasing drugs and prostaglandins, while mechanical methods include hygroscopic dilators and Foley catheters. However, these approaches are associated with certain drawbacks and potential adverse effects.^3,4 Despite their widespread use, prolonged labour and its complications remain prevalent, underscoring the need to explore alternative interventions. Ongoing advances in maternal health research continue to inform best practices and contribute to improved outcomes for mothers and neonates.⁵

Magnesium sulfate, also known as Epsom salt, has garnered attention across multiple medical disciplines due to its diverse therapeutic properties.⁶ It is typically administered intravenously or intramuscularly, but topical administration is also possible. A recent clinical trial conducted in 2023 reported that topical magnesium sulfate application significantly reduced the duration and intensity of labour pain, without notable adverse effects on either the mother or the fetus.⁷ Experimental findings have similarly demonstrated that vaginal application of magnesium sulfate can enhance cervical effacement and dilatation, as well as reduce the duration of labour stages.⁸ In a separate study, topical administration at the onset of the latent phase was associated with an increased Bishop score and a shorter latent phase, ultimately contributing to a reduction in total labour duration.⁹

Given the longstanding clinical priority of minimising labour duration, alleviating pain, and preventing complications related to prolonged labour, it is essential to investigate evidence-based interventions that support maternal care. Accordingly, this meta-analysis was conducted to synthesise existing data and evaluate the effectiveness of vaginal magnesium sulfate administration during labour.

2. Method

This systematic review was conducted and reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.¹⁰

2.1. Study inclusion and exclusion criteria

The research question was structured using the Population, Intervention, Comparator, Outcomes, and Study Design (PICOS) framework as follows: (1) Population: pregnant women; (2) Intervention: administration of vaginal magnesium sulfate; (3) Comparator: placebo or usual care; (4) Outcomes: labour progress and pain outcomes measured using the Numeric Rating Scale (NRS), Visual Analogue Scale (VAS), and mean changes from baseline; (5) Study design: randomised clinical trials.

Studies were excluded if they involved animal subjects, were secondary analyses of published trials, reviews, case reports, or abstracts without sufficient data. Trials that did not report relevant outcomes or lacked sufficient detail for data extraction were also excluded. All randomised trials investigating the effectiveness of topically administered magnesium sulfate were considered eligible, irrespective of publication status, year, language, or region.

2.2. Search strategy

A comprehensive literature search was conducted in MEDLINE/PubMed, the Cochrane Central Register of Controlled Trials (CENTRAL), Web of Science, Scopus, and Google Scholar. The search was completed on 30 July 2024 and updated during the peer review process, with a final update on 13 January 2025. Additional sources included the reference lists of relevant trials and systematic reviews.

Search terms included Medical Subject Headings (MeSH), synonyms, and keywords identified in consultation with domain experts. Boolean operators were used to optimise sensitivity and specificity, and the search syntax was adapted for each database. The search algorithm was initially developed for PubMed and subsequently modified for use in the other databases.

In cases where full-text access was unavailable, study authors were contacted directly. Two reviewers independently conducted the search process to reduce selection bias, with disagreements resolved through discussion or, when necessary, consultation with a third reviewer.

2.3. Study selection

All retrieved records were compiled and de-duplicated using Microsoft Excel. Two reviewers independently screened titles and abstracts for potential eligibility. Full-text articles were obtained for studies deemed relevant by either reviewer. In cases where eligibility could not be determined from the title or abstract, the full text was assessed. Disagreements were resolved through discussion; unresolved cases were adjudicated by a third reviewer [Fig. 1].

Fig. 1.

PRISMA flow diagram illustrating the study selection process for inclusion in the systematic review and meta-analysis.

2.4. Data extraction

Two reviewers independently extracted data using a standardised data extraction form. Extracted data included study author, year of publication, number of participants, intervention and comparison groups, outcomes assessed, and key findings. Data were initially recorded in Microsoft Excel and then transferred to Review Manager (RevMan), version 5.4, for statistical analysis.

A custom data extraction tool was developed to guide the process and ensure consistency across studies. The tool helped minimise potential errors and bias. Discrepancies in data extraction were discussed among the reviewers and, if needed, a third reviewer was consulted until consensus was reached. Final decisions were based on joint review and comparison of extracted data.

2.5. Outcomes

The primary outcomes assessed were the mean differences in cervical dilatation and effacement following the intervention, as well as the duration of the active phase and second stage of labour. Secondary outcomes included the rate of vaginal delivery, labour pain, and reported side effects.

2.6. Assessment of bias risk and evidence certainty

The methodological quality of the included studies was assessed using the Cochrane Risk of Bias version 2 (RoB 2) tool.¹¹ Two reviewers independently evaluated each study for potential sources of bias, rating them as “low risk,” “some concerns,” or “high risk.” The assessment considered five domains: bias arising from the randomisation process, deviations from intended interventions, missing outcome data, outcome measurement, and selection of the reported results. Disagreements between reviewers were resolved through discussion until consensus was reached.

The certainty of evidence for the primary outcomes was evaluated using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. This tool classifies evidence into four levels: high, moderate, low, or very low. Evidence from randomised trials initially receives a “high” rating and may be downgraded based on factors such as risk of bias, inconsistency (I² statistic >50%), indirectness, imprecision (e.g. confidence intervals [CI] including the null value), or publication bias. Conversely, the rating may be upgraded if there is a large magnitude of effect, evidence of a dose–response relationship, or if all plausible confounding would reduce a demonstrated effect.¹² Two reviewers conducted the GRADE assessments independently and resolved any discrepancies through discussion.

2.7. Ethical considerations

The research team adhered to established scientific integrity standards and took care to avoid any form of fabrication, falsification, or plagiarism (FFP) during the planning, conduct, reporting, and publication stages of this review.¹³

2.8. Statistical analysis

All statistical analyses were conducted using Review Manager (RevMan), Version 5.4 (The Cochrane Collaboration, Oxford). Both fixed-effects and random-effects meta-analyses were performed to account for within- and between-study variance. For dichotomous outcomes, the risk ratio and corresponding 95% CI were calculated using the Mantel–Haenszel method. For continuous outcomes, the mean difference (MD) and 95% CI were calculated, with weighting based on the inverse variance method.

Pooled effect estimates were presented using forest plots, and statistical significance was set at a P-value of <0.05 (two-tailed). Heterogeneity was assessed using the I² statistic, which quantifies the proportion of variability attributable to between-study differences. A fixed-effects model was used when I² was below 50%. For values exceeding 50%, a random-effects model was applied, and subgroup analyses were conducted to explore the sources of heterogeneity. In cases where relevant data (e.g. means or standard deviations) were not reported, study authors were contacted to obtain the missing information.

3. Results

A total of 1,029 articles were initially identified through the database search. After removing duplicates, 617 records remained and were screened for eligibility. Following a detailed review, seven randomised controlled trials were included in the systematic review, of which five were eligible for inclusion in the meta-analysis [Fig. 1]. Two studies were excluded from the meta-analysis. In the study by Rouhzandeh et al., the sample included both primiparous and multiparous women.¹⁴ Similarly, in the study by Saadati et al., not only did the participants include both primiparous and multiparous women, but the method of administering magnesium sulfate also differed from the other included studies.¹⁵

The studies were published between 2018 and 2024.^14,15,16,17 All studies were conducted in Iran and involved low-risk pregnant women, most of whom were primiparous and at the onset of either the active or latent phase of labour.^7,8,14,16,17 In two studies, participants included both primiparous and multiparous women.^14,15 The sample sizes ranged from 60 to 98 participants.^8,16,17 Six studies employed a similar intervention method, in which 10 mL of 50% magnesium sulfate solution was poured directly onto the cervix during vaginal examination using a needleless syringe. Participants were then asked to remain in bed for at least 30 minutes to facilitate absorption. In contrast, the study by Saadati et al. applied the solution using a cotton swab soaked in 5 mL of magnesium sulfate, which was placed at the cervical site.¹⁵ In all control groups, distilled water was used, except in one trial, where normal saline was applied instead [Table 1].

Table 1.

Characteristics of the randomised controlled trials included in the systematic review.^{7,8,9,14,15,16,17}

Author and publication year	participants	Intervention group	Control group	Outcome(s)	Finding(s)	Risk of bias
Fakor et al. 7 (2023)	70 primiparous women, 18–35 years, gestational age between 37–40 weeks, in active labor phase, no intake history of calcium channel blocker and narcotic drugs, fetal estimated weight of 2500–4000 grams, and BMI of 19.8–30	N = 35 10 ccs of Magnesium sulfate 50 % was placed on the cervix by using a 10 cc syringe in the dilation of the cervix 5–6 cm, 7–8 cm, and 9–10 cm	N = 35 A placebo (sterile water) in a similar way and amount was used	Length of the First and second stage of labor Apgar score, Labor pain	Lower labor pain and shorter duration of labor stages in the intervention group compared to the control group No difference in neonatal outcomes in two groups	Some concerns
Haji-Seyed-Javadi et al. 17 (2024)	98 primiparous women in active labor, 18 to 35 years old, term gestational age, singleton fetus, cephalic presentation, estimated fetal weight, 2500 to 4000 grams, spontaneous BMI of 19.8 to 30, not having any underlying dangerous diseases	N = 49 In the dilatation of the uterus, at least 5 cm, 10 cc of magnesium sulfate 50% was poured on the cervix through a syringe during the vaginal examination, and in order to better absorb the medicine, the mother was asked to stay in bed half an hour after using the medicine.	N = 49 Placebo (distilled water) was poured on the cervix through a 10 cc syringe in the same way as the intervention group	Length of the active phase, APGAR score, delivery mood, cervical dilatation and effacement after intervention, perineal lacerations	More dilatation and effacement of the cervix and a shorter length of the active phase of labor in the intervention group compared to the control group No difference in the rate of normal delivery, APGAR score and perineal lacerations between the two groups	High
Heydari et al. 16 (2018)	60 pregnant women aged 18 to 35, primiparous, gestational age 37 to 42 weeks, live single fetus, cephalic presentation, BMI 19.8 to 30, no use of narcotic drugs and painkillers in the last 48 hours, estimated fetal weight 2500 to 4000 grams	N = 30 10 cc mgso4 50% on cervix in active phase In cervical dilatation of 3–5 cm, 10 cc of 50% magnesium sulfate was sprinkled on the cervix during the examination. In such a way that the entire cervix was covered with it.	N = 30 Distilled water was used as a placebo in the same way	Length of the active phase of labor, cervical dilatation and effacement after intervention, labor pain, side effects	More dilatation and effacement of the cervix and, shorter length of the active phase of labor, and less labor pain in the intervention group compared to the control group No difference in side effects in both groups. No reporting of serious complications and No negative effect on contractions in the intervention group	Some concerns
Heydari et al. 8 (2019)	72 primiparous women aged 18 to 35 years, gestational age 37 to 42 weeks, Live singleton fetus with cepharic presentation, Cervical dilatation 3 to 5 cm, estimated fetal weight 2500 to 4000 grams, spontaneous beginning of the labor process, Low risk pregnancy, BMI between 19.8 to 30	N = 36 In Bishop score of 5, 10 cc of 50% magnesium sulfate was poured on the cervix through a syringe during the vaginal examination. In cases where the amnion sac ruptured half an hour after the intervention, another 10 cc of magnesium sulfate was poured on the cervix	N = 36 Distilled water placebo was used in the same way as magnesium sulfate	Length of the active phase, second, and third stage of labor, APGAR score, delivery mood, cervical dilatation and effacement after intervention, mode of delivery, Hemoglobin drop	More dilatation and effacement of the cervix and, shorter length of the active phase of labor, and less drop in hemoglobin level in the intervention group compared to the control group No difference in duration of second and third stages of labor, the mode of delivery and APGAR score in the two groups	Some concerns
Heydari et al. 9 (2020)	60 low-risk primiparous pregnant women with term pregnancy, 18–35 years old, singleton fetus in cephalic presentation, no history of infertility, estimated fetal weight within the normal range, no underlying maternal diseases, spontaneous onset of labor, BMI 18.5–24.9	N = 30 In the latent phase of labor (Bishob score less than 5 and cervical dilatation less than 2 cm) 10 cc of 50% magnesium sulfate was poured onto the cervix during a vaginal examination through a syringe, and the mother was asked to stay in bed for at least half an hour	N = 30 A placebo (10 cc sterile water) in a similar way was used	Bishop score, cervical dilatation, and effacement after intervention, perineal lacerations, APGAR, Length of the latent and active phases of labor, Hemoglobin drop	Shorter duration of the latent and active phases of labor and more Bishop score in the intervention group compared to the control group No difference in other outcomes in two groups	Some concerns
Rouhzendeh et al. 14 (2024)	98 women aged 18 to 39 years with term singleton pregnancies (37–42 weeks), no history of cesarean section, and 1–2 prior vaginal births or primiparity. Eligibility included estimated fetal weight of 2500–4000 g, cephalic presentation, fetal head station between -2 and 0, and cervical effacement of 40–70%.	N = 49 At the onset of the active phase of labor (4–5 cm dilation), 10 mL of 50% magnesium sulfate was applied to the cervix using a prefilled syringe during a vaginal exam. Participants lay down for 30 minutes to enhance absorption. If the amniotic sac ruptured within this time, the intervention was repeated.	N = 49 Placebo (distilled water)	labor duration, childbirth experience	In the IG, labor duration was significantly shorter, and the childbirth experience score was higher compared to the CG	Low
Saadati et al. 15 (2024)	Participants were 104 women aged 18–35 years with a BMI of 18.5–30, 34–42 weeks gestation, a singleton fetus weighing 2500–4000 g, and a Bishop score under 5. Those requiring cesarean delivery or not consenting were excluded.	A cotton swab soaked in magnesium sulfate was applied to the cervix, and the Bishop score was reassessed after 3 hours.	N = 52 Placebo (Normal saline-filled vials)	Bishop score, Labor duration, and active phase duration.	The secondary Bishop score was significantly higher in the IG. Additionally, the total time of vaginal delivery was significantly shorter in the IG compared to the CG. There was no significant difference between the groups regarding the delivery method.	Some concerns

IG = intervention group; CG = control group; BMI = body mass index.

3.1. Assessments of bias risk

One study was rated as having a high risk of bias, while another was assessed as low risk.^14,17 The remaining studies were rated as having some concerns.^7,8,9,15,16 All studies raised concerns regarding the randomisation process, as the method of allocation concealment was not clearly described. Only one study reported the use of sealed envelopes for allocation.¹⁴ One study presented concerns in the domain of missing outcome data due to insufficient information regarding the number of participants included in the final analysis.¹⁷ The risk of bias in other domains was generally low [Table 1].

3.2. Findings of the meta-analysis

The meta-analysis, using a fixed-effects model, indicated that topical magnesium sulfate increased cervical dilatation by a mean of 2.27 cm compared to the control group, a statistically significant finding (MD: 2.27 cm, 95% CI: 1.98 to 2.56; P <0.00001). No significant heterogeneity was detected among the included studies (χ² = 0.10, I² = 0%; P = 0.95) [Fig. 2].

Fig. 2.

Forest plots of the effect of topical magnesium sulfate on cervical dilatation (A and effacement (B two hours after intervention.

Regarding cervical effacement, the pooled analysis using a random-effects model demonstrated a statistically significant increase of 15.30% in the intervention group compared to the control group (MD: 15.30%, 95% CI: 7.79 to 22.82; P <0.0001). Significant heterogeneity was observed between studies (χ² = 12.56, I² = 84%; P = 0.002). Sensitivity analysis showed that no single study significantly influenced the overall findings. Publication bias was not assessed due to the limited number of included studies.

3.3. Effect on the length of the active phase and second stage of labour

dA meta-analysis of four trials involving 300 women indicated that the use of topical magnesium sulfate at the beginning of the active phase of labour significantly reduced its duration by a mean of 1.63 hours compared to the control group (MD: -1.63 hours, 95% CI: -2.15 to -1.11; P < 0.00001). Due to substantial heterogeneity (χ² = 11.28, I² = 73%; P = 0.01), a random-effects model was applied. The duration of the second stage of labour was also shorter in the magnesium sulfate group, by a mean of 22.69 minutes; however, this difference was not statistically significant (MD: -22.69 minutes, 95% CI: -71.61 to 26.23; P = 0.36) [Fig. 3].

Fig. 3.

Forest plots of the effect of topical magnesium sulfate on the length of (A active phase and (B second stage of labour.

3.4. Effect on vaginal delivery rate

The use of topical magnesium sulfate at the onset of active labour did not result in a significant increase in the rate of vaginal delivery compared to placebo (risk ratio: 0.94, 95% CI: 0.79 to 1.11; P = 0.46). Owing to the absence of heterogeneity (χ² = 0.17, I² = 0%; P = 0.68), a fixed-effects model was used.

3.5. Effect on labour pain

Labour pain was assessed using a visual analogue scale with a 10 cm range, two hours after the intervention. The meta-analysis revealed a statistically significant reduction in pain scores in the magnesium sulfate group compared to the control group (MD: -1.50, 95% CI: -2.48 to -0.53; P = 0.002). A random-effects model was applied due to significant heterogeneity between studies (χ² = 8.45, I² = 76%; P = 0.01).

3.6. Adverse effects

Only one study assessed adverse effects in both intervention and control groups.¹⁶ However, the included trials were not designed or powered to evaluate safety outcomes, limiting the ability to detect significant differences. As a result, findings are presented qualitatively. Reported side effects included nausea, vomiting, palpitations, drowsiness, cervical swelling, hot flushes, and muscle weakness. Most of these were reported in both groups, except for hot flushes, which were more commonly observed in the magnesium sulfate group. Post-intervention, 23.3% of participants in the magnesium sulfate group and 16.6% in the control group experienced hot flushes. However, there was no statistically significant difference between groups regarding the incidence of adverse effects. Due to the underpowered nature of these studies for detecting safety outcomes, interpretation of adverse effects should be approached with caution and requires further evidence.

3.7. Certainty of evidence

The certainty of evidence for cervical dilatation two hours after intervention and for the rate of vaginal delivery was rated as low, based on two downgrades due to serious risk of bias and imprecision. Similarly, evidence for labour pain and the duration of the second stage of labour was also graded as low due to inconsistency and imprecision. Finally, the certainty of evidence for the duration of the active phase and cervical effacement two hours after intervention was assessed as very low due to downgrades for serious risk of bias, inconsistency, and imprecision.

4. Discussion

This meta-analysis represents an initial effort to evaluate the effectiveness of vaginal administration of magnesium sulfate during labour using the most up-to-date available evidence. Five randomised controlled trials were included. Magnesium sulfate is a well-established agent in maternal–fetal medicine, with applications across various clinical scenarios in pregnancy.⁵

The results indicated that topical magnesium sulfate significantly increased cervical dilatation by a mean of 2.27 cm two hours after administration. Additionally, analysis of four trials involving 300 women showed that applying topical magnesium sulfate at the onset of the active phase of labour significantly reduced its duration by 1.63 hours compared to the control group. This finding is clinically relevant, as prolonged labour is associated with an increased risk of maternal and neonatal complications, including infection, postpartum haemorrhage, and emergency caesarean section.¹⁸

Evidence has demonstrated that an extended second stage of labour increases the risk of neonatal sepsis, low 5-minute Apgar scores, birth depression, and admission to the neonatal intensive care unit.^19,20,21 Maternal complications associated with prolonged second-stage labour include admission to the intensive care unit, postpartum haemorrhage, episiotomy, third- or fourth-degree perineal laceration, chorioamnionitis, and endometritis.^22,23,24 Neonatal risks also encompass asphyxia, intensive care admission, neonatal sepsis, seizures, and low Apgar scores.^22,25,26 Furthermore, prolonged labour is frequently linked with negative maternal experiences during childbirth.²⁷

At present, there is limited evidence on the effect of topical magnesium sulfate on labour progression, with most existing literature focusing on systemic administration. Until recently, there has been a lack of robust comparative studies examining topical magnesium sulfate against placebo or standard care in labour management. However, systemic magnesium sulfate has been associated with prevention of preterm birth and management of preeclampsia.^28,29 The proposed mechanism for its effects includes calcium channel blockade, leading to smooth muscle relaxation. Additionally, magnesium sulfate promotes the expression of water channel proteins via activation of protein kinase A and cyclic adenosine monophosphate (cAMP), contributing to its osmotic effects. This may reduce oedema, soften the cervix, and enhance effacement.^9,30 However, it should be noted that variability in the individuals administering the interventions—such as midwives, obstetrics and gynaecology assistants, students, and midwifery faculty—may have influenced outcomes.

The pooled analysis of two trials demonstrated a statistically significant reduction in pain following topical magnesium sulfate use. A previous meta-analysis published in 2022 reported that systemic magnesium sulfate administration significantly reduced Visual Analogue Scale pain scores among women undergoing general, spinal, or epidural anaesthesia for caesarean section (P < 0.05).³¹ Magnesium sulfate is thought to exert its analgesic effects by antagonising the N-methyl-D-aspartate (NMDA) receptor, and by relaxing smooth muscle through inhibition of acetylcholine-induced depolarisation at the neuromuscular junction.^32,33

Magnesium sulfate baths, commonly referred to as Epsom salt soaks, have been traditionally used as a topical remedy for musculoskeletal and dermatological conditions. They are thought to reduce pain, inflammation, and general discomfort. However, no clinical studies have conclusively demonstrated their antimicrobial, analgesic, or anti-inflammatory properties.³⁴ Magnesium sulfate may reduce cervical oedema and pain through increased cAMP production and enhanced water absorption at the cervical site.³⁵

The findings from two included studies indicated no statistically significant difference in the rate of spontaneous vaginal delivery between the intervention and control groups.^8,17 Furthermore, this meta-analysis did not identify any serious adverse effects associated with vaginal administration of magnesium sulfate when compared to the control group. The available data suggest that the application of topical magnesium sulfate in limited doses does not negatively impact maternal haemodynamics or respiratory function. Nevertheless, healthcare professionals attending to pregnant women should remain vigilant for potential adverse effects and be adequately prepared to address complications should they arise. Such preparedness can contribute to improved outcomes while mitigating potential risks.

Rouhzandeh et al. noted that participants may cough, sneeze, or move during bed rest, potentially leading to leakage of the administered solution. Therefore, it has been suggested that future studies consider alternative methods, such as the use of cervical dilators, gauze, or pads soaked in magnesium sulfate or distilled water to improve drug retention.¹⁴ In line with this recommendation, the study by Saadati et al. employed soaked pads for drug administration.¹⁵

All included studies exhibited some concerns in the domain of randomisation, as none reported adequate information regarding allocation concealment. Future trials should ensure rigorous randomisation procedures and transparent reporting to reduce the risk of bias. Using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) methodology, we assessed the certainty of evidence for each comparison, incorporating relative effect estimates, total sample size, and the number of contributing publications. Although the results suggest a potential benefit of magnesium sulfate on cervical dilatation, effacement, and duration of the active phase of labour, the overall certainty of evidence was low to very low. This reflects methodological limitations and imprecision, indicating that further research is likely to affect both the magnitude and the confidence in these findings.

Several strengths of the current review may help reduce the risk of bias. These include the use of independent double-blinded screening procedures, consensus resolution of discrepancies, comprehensive searches across multiple databases, and the absence of time or language restrictions. Potential publication bias was mitigated through extensive searching of both indexed literature and grey sources, including unpublished trials.

Nonetheless, several limitations must be acknowledged. The meta-analysis is based on a small number of trials, each with relatively limited sample sizes. Variability in concurrent interventions during labour may have introduced additional heterogeneity. Importantly, all seven included studies were conducted in Iran, which may affect the generalisability of the findings to other populations and settings. Broader international collaboration is recommended to validate these findings across different cultural and healthcare contexts. Dissemination of these results at international conferences may encourage replication studies in other countries and help strengthen the evidence base.

Moreover, existing studies were not adequately powered to evaluate the safety profile of topical magnesium sulfate use during labour. Therefore, future large-scale, well-designed trials are needed to investigate both the effectiveness and safety of this intervention in diverse populations.

5. Conclusion

Topical magnesium sulfate appears to have a beneficial effect on cervical dilatation and effacement, reduces the duration of the active phase of labour, and alleviates labour pain. These findings may inform future research priorities and contribute to the development of clearer clinical guidelines for the use of this intervention. Given its accessibility and ease of administration, magnesium sulfate may represent a practical option in maternity care settings that do not require specialised expertise. However, the current evidence remains inconclusive due to the limited number of studies, small sample sizes, methodological limitations, and heterogeneity across trials. As such, these findings are not yet generalisable to broader populations. Well-designed, adequately powered randomised controlled trials conducted in diverse international settings are needed to confirm the effectiveness and safety of this intervention and to better define its clinical utility.

Authors' Contribution

Somayeh Makvandi: Conceptualization, Methodology, Data Curation, Investigation, Formal Analysis, Writing - Original Draft, Writing - Review & Editing. Mona Larki: Conceptualization, Methodology, Data Curation, Investigation, Writing - Original Draft, Writing - Review & Editing. Elham Manouchehri: Conceptualization, Methodology, Data Curation, Investigation, Writing - Original Draft, Writing - Review & Editing. Mahdieh Razi: Conceptualization, Writing - Original Draft, Writing - Review & Editing. Samaneh A. Mofrad: Conceptualization, Writing - Original Draft, Writing - Review & Editing.

Acknowledgement

The authors are grateful to the researchers whose publications were used to write this article. The authors acknowledge the use of artificial intelligence-based tools exclusively for language enhancement following the initial drafting of the manuscript.

Ethics Statement

The review protocol was registered with the International Prospective Register of Systematic Reviews (CRD42024577006).

Artificial Intelligence Declaration

An artificial intelligence tool (QuillBot, Learneo, Inc.) was used to improve grammar and language fluency only.

Data Availability Statement

All data generated or analysed during this study are included in this manuscript.