https://orcid.org/0009-0003-5876-5567
Figures
Abstract
Introduction
Any intervention aimed at maximizing the spontaneous onset of labor and preventing formal induction will be beneficial to the client and welcomed by the provider, because it reduces postmaturity and formal labour induction.
Methods
We recruited and randomized 312 uncomplicated singleton pregnancies at 38 weeks of gestation into three groups: membrane sweep (MS), cervical massage (CM), and sham sweep (control). Each intervention was administered at 39 weeks and repeated at 40 weeks of gestation if spontaneous labor, defined as a Modified Bishop’s Score of ≥7, did not occur. (Sri Lanka clinical trials registry - SLCTR/2020/003).
Results
The membrane sweep reduced the need for formal induction, whereas cervical massage did not. (MS vs C RR = 1.4195, 95% CI = 1.0326–1.9513, p = 0.0310; MS vs C OR=1.8739, 95% CI = 1.0664–3.2927, p = 0.0290; Number Needed to Treat = 7; CM vs C RR = 1.2043, 95% CI = 0.8598–1.6867, p = 0.2795). “Survival without spontaneous labor,” was lower after the membrane sweep than in controls overall (MS vs C – p = 0.007; CM vs C – p = 0.261), among primiparous (MS vs C p = 0.047; CM vs C p = 0.269) and multiparous (MS vs C p = 0.038; CM vs C p = 0.456) women. The membrane sweep and cervical massage were safe concerning feto-maternal complications and both reduced hospital-stay duration among multiparous women (MS vs C p < 0.0001, 95% CI = 0.5293–1.1791; CM vs C p < 0.0001, 95% CI = 0.6816–1.3552). There was no increased risk of emergency cesarean delivery, oxytocin augmentation, uterine hyperstimulation, postpartum bleeding, maternal pyrexia, or Apgar score < 7 at 5 minutes (p > 0.05). The membrane sweep was less acceptable compared to cervical massage, regardless of parity (MS vs C Primi p = 0.001, Multi p = 0.0216).
Citation: Madugalle TMSSB, Jayasundara DMCS, Jayawardane IA (2025) Comparing membrane sweep and cervical massage in preventing the need for formal labour induction in uncomplicated pregnancy at term: Secondary analysis of a randomized controlled trial. PLoS One 20(5): e0324172. https://doi.org/10.1371/journal.pone.0324172
Editor: Nishel Mohan Shah, Imperial College London, UNITED KINGDOM OF GREAT BRITAIN AND NORTHERN IRELAND
Received: July 13, 2024; Accepted: April 17, 2025; Published: May 20, 2025
Copyright: © 2025 Madugalle et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: All relevant data are within the article and its Supporting Information files.
Funding: The author(s) received no specific funding for this work.
Competing interests: The authors have declared that no competing interests exist.
Introduction
Induction of labor (IOL) should be considered when continuing the pregnancy is comparatively less beneficial than delivery. IOL is the most frequent obstetric intervention, reportedly applied in 20–25% of all pregnancies worldwide [1,2]. In Sri Lanka, the incidence is estimated to be around 32.8% by 41 weeks of gestation. IOL is associated with increased maternal complications and cesarean sections [3]. Elective inductions undertaken earlier than 39 weeks of gestation may lead to longer labors, prolonged latent stages, patient and practitioner impatience, increased costs, and higher neonatal morbidity [4,5]. IOL medicalizes the birthing process, impacting healthcare system resources and negatively affecting the birth experience for the family.
Any simple, harmless, and effective intervention that promotes the spontaneous onset of labor would be highly beneficial. It would help prevent complications associated with formal induction and allow the mother to experience a more natural childbirth with minimal interventions. Therefore, the National Institute for Health and Care Excellence (NICE) recommends offering a membrane sweep to all suitable pregnant women at 39 weeks, with additional sweeps as needed if labor does not commence. It also recommends cervical massage if the examining finger cannot pass through the closed cervical os. [6].
This recommendation is based on the premise that cervical massage is as effective as a membrane sweep. However, there is no well-conducted research designed to compare the intervention-specific effects and its utility either as a method of induction or as an adjunct to prevent formal induction. Moreover, available physiological studies raise serious concerns.
Both the membrane sweep and cervical massage are based on the premise that they induce a local release of prostaglandins. This has been evidenced by in-vitro stimulation studies on strips of cervical tissue [7,8]. Prostaglandins interact complexly with cervical cells and the extracellular matrix. Their local concentrations lead to cervical softening, shortening, and dilation. Additionally, prostaglandins stimulate myometrial receptors, triggering rhythmic uterine contractions.
Fetal membranes and the decidua are critical sites for intrauterine prostaglandin synthesis. These mechanical methods cause disruption at these sites, leading to prostaglandin synthesis and release [9,10]. The degree of disruption is important, as shown by the work of Marc J.N.C et al., who compared extra-amniotic Foley catheter induction with and without the instillation of cellulose gel. The cellulose gel, which had a much greater extra-amniotic spread, separated a correspondingly larger area of chorio-amnion from the decidual surface compared to just the inflated balloon of a Foley catheter. This resulted in a greater rise in prostaglandin levels in peripheral blood at 5 minutes, which gradually reduced over the next 12 hours [11]. This finding correlated with the work of Manabe et al., which suggested that a larger volume balloon may produce greater separation and a larger rise in prostaglandin levels. Additionally, a larger balloon would stretch the cervix more [12].
A well-conducted membrane sweep, which separates a significantly larger area of the chorio-amnion from the decidua and stretches the cervix more, likely causes a much greater rise in prostaglandin levels compared to a cervical massage. The cervical massage is limited to external stimulation of the cervix without any disturbance of the chorio-decidual interface. Additionally, the membrane sweep stretches the cervix, triggering the Ferguson reflex, which leads to pulsatile oxytocin secretion from the posterior pituitary, unlike the cervical massage [13].
The National Institute for Health and Care Excellence (NICE) now recognizes the balloon catheter as a mechanical induction method. There are variants, such as the double balloon and single balloon, but evidence is limited in determining the superiority of one over the other [14]. Currently, the membrane sweep is considered an adjunct to the induction process rather than a standalone mechanical induction method.
Although the membrane sweep is widely applied in Sri Lanka, cervical massage has not gained much popularity, and neither method has been standardized or well described in the literature. Therefore, we conducted a randomized controlled trial to compare the intervention-specific efficacy of the membrane sweep and cervical massage in preventing the formal induction of labor.
Methods
A randomized, single-blind controlled trial was conducted at De Soysa Hospital for Women, Colombo 08, Sri Lanka, from 1st of February to 31st of July, 2020 (Trial Registration No: SLCTR/2020/003, Date of registration: 22nd January, 2020). A total of 349 uncomplicated singleton pregnancies between 38–40 weeks of gestation were selected via simple random sampling from the antenatal clinic at the Professorial Obstetrics and Gynaecology Unit. Sample size estimation was based on prior research indicating an increase in spontaneous labor from 75% to 90% following membrane sweeping (Alpha = 0.05, Beta = 0.8, Minimum sample size per group = 100). Thirty-seven women were excluded due to predefined eligibility criteria (Tables 1 and 2).
312 prospective participants were provided, written information with verbal clarifications where necessary with one week period to consider participation. The principal investigator was available for consultation over the phone during that one week, during work hours and weekend. At the end of the 7-day period they were re-interviewed, further clarifications were provided as required, and consent forms were signed, in the presence of the principal investigator. All 312 women were recruited into the study and randomized into three groups using a random number sequence generated using Research Randomizer (https://www.randomizer.org). Sequentially numbered, equal-sized red color cards with the allocated intervention printed on the reverse side, were stored in an opaque container until the participants signed the consent forms. Randomization was performed by the three investigators. The first group received a membrane sweep (MS), the second group received a Cervical Massage (CM), and the third group, serving as the control, underwent a sham sweep following a pelvic examination to record the Bishop’s score at recruitment.
Interventions were administered at 39 weeks of gestation, and repeated at 40 weeks if spontaneous labor did not occur within one week (Table 3). Stringent safety protocols were implemented to withdraw participants in cases of latex allergies, cervical tears, vasovagal attacks, uterine rupture, maternal or fetal infections, or any psychological concerns. All adverse events were managed per standard unit protocols, serious adverse events were reported to a Data and Safety Monitoring Board composed of two external obstetricians and an external biostatistician.
Participants were blinded to the specific intervention received, and the intervention acceptability was assessed. All interventions, being vaginal, were performed during digital vaginal examination with prior consent, and no additional blinding methods were utilized. The principal investigator provided counselling based on a template and performed all interventions to ensure uniformity.
Participants were followed up every third day as outpatients until 40 + 6 weeks of gestation. A Modified Bishop’s Score of 6 or less indicated no spontaneous labor, prompting formal induction, using either a Foley catheter or prostaglandin vaginal tablet, as an inpatient. Participants going into spontaneously labor, i.e., achieving a Modified Bishop’s Score of 7 or more, were admitted for labour management. All participants were managed according to standard unit protocols and monitored according to the study protocol till 24 hours postpartum for complications (Table 4).
Maternal acceptability was assessed using a pre-validated, interviewer-administered questionnaire, consisting of four Likert scale items. This questionnaire, developed by the principal author, is an adaptation of the seven-fold conceptual framework for the acceptability of a healthcare intervention published by Sekhon et al. The seven components are affective attitude, burden, perceived effectiveness, self-efficacy, ethicality, intervention coherence, and opportunity cost. The first five components were extracted due to their patient-focused nature [15].
The four-item questionnaire was developed using five-step pre-validation method for patient-reported outcome instruments, published by Prior et al., [16] and the discriminant content validity method for theory-based instruments, published by Johnston et al., [17]. It was assessed for answerability, comprehensibility, and relevance using adaptations from the Think-Aloud studies published by French et al., [18], and Green and Gilhooly [19]. The resultant questionnaire was validated in a pilot study with 202 pregnant women selected using the same exclusion and inclusion criteria as the current study (S-CVI = 0.875, Cronbach’s alpha = 0.876).
Given the temporal evolution of acceptability from before, during, and after the intervention described by Sekhon et al, the questionnaire was administered 24 hours postnatally to capture an overall impression. Each item was scored from 1 to 5, yielding a total score for each participant.
Data was analyzed using SPSS 26. Comparisons between the control and the intervention groups were performed separately. Demographic characteristics, mean acceptability scores, duration of hospital stay, and mean Apgar score at 5 minutes of the three groups were compared using t-tests to and P values with 95% confidence intervals were reported.
Spontaneous labor rates, emergency cesarean delivery rates, postpartum hemorrhage rates, maternal pyrexia rates, and rates of neonates with an Apgar score of less than 7 at 5 minutes after birth were compared using proportions and the Chi-square test, and P values with 95% confidence intervals were reported. Kaplan-Meier survival plots for proportion of subjects without spontaneous labour, after membrane sweep, cervical massage, and controls were generated. The Log-Rank test compared survival distributions between intervention groups and controls separately. P values of <0.05 were deemed statistically significant.
Formal induction rates after membrane sweep and cervical massage were compared to controls individually, with odds ratios (OR), relative risk ratios (RR), Control and experiment event rates, attributable risk ratio, and number needed to treat (NNT) for each intervention calculated using contingency tables. Subgroup analysis was conducted based to parity.
The study was reviewed and approved by the Ethics Review Committee of the Faculty of Medicine, University of Colombo on October 17, 2019, for application no. PROTOCOL-019-064.
Results
Out of the 349 women selected, 1 had a fetus with a cardiac anomaly, 3 had abnormal liquor, and 7 had small-for-gestational-age or growth-restricted fetuses. During the initial pelvic examination, it was not possible to insert the examining finger into the cervical canal due to tightly closed cervices in 26 women, making membrane sweep impossible in these women. The Cervical Massage (CM), Membrane Sweep (MS), and Control (C) groups respectively had 106, 104, and 102 subjects. One participant in the CM group, 2 in the MS group, and 1 in the C group withdrew consent. Two women in the MS group and 3 in the CM group delivered at other hospitals and were excluded from the study. Therefore, 100, 102, and 101 subjects in the MS, CM, and C groups respectively were included in the final analysis according to the originally assigned groups (Fig 1). All three groups had similar demographic characteristics (Table 5). All interventions were promptly administered without any decision-to-intervention delay. All participants had satisfactory maternal and fetal conditions before the interventions.
Spontaneous labor (i.e., prevention of formal induction) occurred in 52% of cases after MS, 44.12% after CM, and 36.63% after the sham sweep. The comparisons showed:
- MS vs C: Relative Risk (RR) = 1.4195, 95% CI = 1.0326–1.9513, p = 0.0310
- MS vs C: Odds Ratio (OR) = 1.8739, 95% CI = 1.0664–3.2927, p = 0.0290
- MS vs C: Number needed to treat (NNT) = 7
- CM vs C: RR = 1.2043, 95% CI = 0.8598–1.6867, p = 0.2795
Subgroup analysis based on parity did not show any statistically significant difference between any methods..
The duration from intervention to diagnosis of spontaneous labor was assessed. Kaplan-Meier survival analysis showed that after a membrane sweep, the proportion of subjects without spontaneous labor was significantly lower compared to controls, regardless of parity. Membrane sweep caused women to undergo spontaneous labor earlier than the controls, while cervical massage did not (Tables 6 and 7).
Analysis of survival plots revealed another interesting trend. Primiparous women required two interventions one week apart for a significant effect, while a single administration sufficed for multiparous women (Figs 2 and 3).
This figure demonstrates changes of the cumulative percentage of primiparous women who remain without going into spontaneous labour plotted against the time from initial intervention.
This figure demonstrates changes of the cumulative percentage of multiparous women who remain without going into spontaneous labour plotted against the time from initial intervention.
The maternal acceptability score of cervical massage was significantly higher than that of the membrane sweep, regardless of parity. Particularly in primiparous women, the difference in acceptability between cervical massage and membrane sweep was highly significant (p = 0.0001) (Table 8).
Emergency Cesarean delivery rates, oxytocin augmentation rates, and uterine hyperstimulation rates were similar in the MS, CM, and C groups during the overall analysis as well as the subgroup analysis according to parity (Table 9).
There was no difference in postpartum bleeding and maternal pyrexia rates between the MS, CM, and C groups (Table 10). In contrast, the duration of hospital stay was significantly shorter in women who had either a membrane sweep (MS) or cervical massage (CM) overall, compared to controls (MS vs C – p = 0.0015, 95% CI = 0.1752–0.7166, CM vs C – p = 0.0197, 95% CI = 0.0603–0.6757).
Both membrane sweep and cervical massage shortened hospital stay in multiparous women only (MS vs C – p < 0.0001, 95% CI = 0.5293–1.1791, CM vs C – p < 0.0001, 95% CI = 0.6816–1.3552). Interestingly, there was no such difference among primipara. APGAR value at 5 minutes was assessed, and all three methods had similar values. There were no neonates with an APGAR <7 at 5 minutes among study participants in any group (p > 0.05, Table 10).
The trial concluded with all participants progressing through the study protocol without any significant adverse outcomes. The study protocol and the anonymized data sets are freely accessible under the CC By 4.0 license: S1 Data– questionnaire data, S2 Data set Multi, S3 Data set Primi, S4 Data– Study protocol [20–22].
Discussion
Induction of labor is currently an in-patient procedure under existing protocols, with only a few units practicing outpatient formal labor induction. Reducing the need for formal induction is highly attractive to pregnant women, obstetricians, and policymakers, as it would lead to significant cost savings, minimal disruptions to the daily lives of pregnant women and their families, and an improved birth experience.
Membrane sweep (MS) was more successful in preventing formal induction compared to controls, whereas no such difference was noted after CM. “Survival analysis” clearly shows that MS was more effective due to the lower numbers of women without spontaneous labor. Since we selected a population where both membrane sweep and cervical massage were possible, we were able to determine the intervention-specific effect on the cervix, allowing for an evidence-based decision when selecting an induction prevention method.
Our findings correlate with the available physiological understanding of cervical ripening and the process of induction of labor. The magnitude of local prostaglandin release depends on the degree of disruption of the chorio-decidual interface and the degree of cervical stretching [23,24]. Membrane sweep disrupts the chorio-decidual interface to a much higher degree compared to cervical massage, where there is no such disruption. The insertion of the examining finger stretches the cervix, increasing local prostaglandin release as well as triggering the Ferguson reflex.
Available literature does not suggest any increased risk of infection during either membrane sweep or cervical massage. Admittedly, the evidence base for cervical massage is quite poor [25].
In an interesting turnout, we found that primiparous women needed two sweeps one week apart to prevent formal induction compared to the single sweep in multiparous women. This may be due to the higher receptiveness and sensitivity of the multiparous cervix and/or the higher initial Modified Bishop’s Score. Since this study was not designed to compare different regimens of membrane sweep, we cannot recommend one regimen over the other. There are a few studies looking into various sweep regimens. Putnam et al. compared a single sweep to weekly sweeps and found no significant difference in rates of spontaneous labor [26]. Another study compared daily sweeps to vaginal Dinoprostone and found that sweeps were more effective and less costly [27]. The authors are conducting ongoing research to compare different regimens.
For multiparous women, both membrane sweep and cervical massage significantly reduced the duration of hospital stay compared to controls in our study. Our data supports the safety profile of both membrane sweep and cervical massage without any added risks. Neonatal parameters also show excellent tolerability of these mechanical methods, though there is no long-term data on the well-being of babies born following the use of membrane sweep or cervical massage.
Both membrane sweep and cervical massage were very safe procedures with minimal adverse events according to our study. The routine practice worldwide is to perform these as outpatient procedures, and our findings reinforce this practice. Admission and monitoring were conducted for research purposes and to objectively assess the safety of these interventions.
To ensure the largest possible prostaglandin release, we recommend the technique for membrane sweeping we adopted for the study. The examining finger should be inserted through the internal cervical os, followed by three circumferential sweeps between the fetal membranes and the decidua, separating the two. The depth of separation should be the length of the examining finger. While one sweep separates the chorio-amnion from the decidua, the two additional sweeps exert a stretching effect on the cervix, maximizing prostaglandin release and triggering the Ferguson reflex.
In conclusion, we recommend the routine administration of a membrane sweep to prevent formal induction in term uncomplicated pregnancies. However, clinicians should be aware of its inherent discomfort and should counsel women about this during delivery planning.
References
- 1.
Martin J, Hamilton B, Ventura S, Osterman M, Kirmeyer S, Mathews T, et al. Births: final data for 2009. National vital statistics reports. 2011.
- 2. Calder AA, Loughney AD, Weir CJ, Barber JW. Induction of labour in nulliparous and multiparous women: a UK, multicentre, open-label study of intravaginal misoprostol in comparison with dinoprostone. BJOG. 2008;115(10):1279–88. pmid:18715414
- 3. Senanayake H, Mariani I, Valente EP, Piccoli M, Armocida B, Businelli C, et al. Outcomes of induction versus spontaneous onset of labour at 40 and 41 GW: findings from a prospective database, Sri Lanka. BMC Pregnancy Childbirth. 2022;22(1):518. pmid:35761191
- 4. Clark SL, Miller DD, Belfort MA, Dildy GA, Frye DK, Meyers JA. Neonatal and maternal outcomes associated with elective term delivery. Am J Obstet Gynecol. 2009;200(2):156.e1–4. pmid:19110225
- 5. Luthy DA, Malmgren JA, Zingheim RW. Cesarean delivery after elective induction in nulliparous women: the physician effect. Am J Obstet Gynecol. 2004;191(5):1511–5. pmid:15547518
- 6. National Institue of Health and Care Excellence. Inducing labour. [Online]. 2021 [cited 2023]. Available from: https://www.nice.org.uk/guidance/ng207/resources/inducing-labour-pdf-66143719773637.
- 7. Kloeck FK, Jung H. In vitro release of prostaglandins from the human myometrium under the influence of stretching. Am J Obstet Gynecol. 1973;115(8):1066–9. pmid:4691466
- 8. Hillier K, Coad N. Synthesis of prostaglandins by the human uterine cervix in vitro during passive mechanical stretch. J Pharm Pharmacol. 1982;34(4):262–3. pmid:6124603
- 9. Keirse M, Turnbull A. The fetal membranes as a possible source of amniotic fluid prostaglandins. Br J Obstet Gynaecol. 1976;83:146.
- 10. MacDonald PC, Porter JC, Schwarz BE, Johnston JM. Initiation of parturition in the human female. Semin Perinatol. 1978;2(3):273–86. pmid:216122
- 11. Keirse MJ, Thiery M, Parewijck W, Mitchell MD. Chronic stimulation of uterine prostaglandin synthesis during cervical ripening before the onset of labor. Prostaglandins. 1983;25(5):671–82. pmid:6611963
- 12. Manabe Y, Manabe A, Takahashi A. F prostaglandin levels in amniotic fluid during balloon-induced cervical softening and labor at term. Prostaglandins. 1982;23:247.
- 13.
Blackburn S. Maternal, Fetal, & Neonatal Physiology ‐ A Clinical Perspective. 3rd ed. Missouri: Saunders Elsevier; 2013.
- 14. Peel MD, Croll DMR, Kessler J, Haugland B, Pennell CE, Dickinson JE, et al. Double-vs single-balloon catheter for induction of labor: systematic review and individual participant data meta-analysis. Acta Obstet Gynecol Scand. 2023;102(11):1440–9. pmid:37417714
- 15. Sekhon M, Cartwright M, Francis JJ. Acceptability of healthcare interventions: an overview of reviews and development of a theoretical framework. BMC Health Serv Res. 2017;17(1):88. pmid:28126032
- 16. Prior ME, Hamzah JC, Francis JJ, Ramsay CR, Castillo MM, Campbell SE, et al. Pre-validation methods for developing a patient reported outcome instrument. BMC Med Res Methodol. 2011;11:112. pmid:21827689
- 17. Johnston M, Dixon D, Hart J, Glidewell L, Schröder C, Pollard B. Discriminant content validity: a quantitative methodology for assessing content of theory-based measures, with illustrative applications. Br J Health Psychol. 2014;19(2):240–57. pmid:24628841
- 18. French DP, Cooke R, McLean N, Williams M, Sutton S. What do people think about when they answer theory of planned behaviour questionnaires? A “think aloud” study. J Health Psychol. 2007;12(4):672–87. pmid:17584818
- 19.
Green C, Gilhooly K. Protocol analysis: practical implementation. In: Handbook of qualitative research methods for psychology and the social sciences. 1996. p. 55–74.
- 20. Madugalle TMSSB, Jayasundara DMCS, Jayawardane IA. Figshare. [Online]. 2025. [cited 2025 Jan 21. ]. Available from: https://figshare.com/articles/dataset/Questionnaire_data_excel_version/28248005?file=51827375
- 21. Madugalle TMSSB, Jayasundara DMCS, Jayawardane IA. Figshare. [Online]. 2025. [cited 2025 Jan 21. ]. Available from: https://figshare.com/articles/dataset/Data_set_multi_xlsx/28243112?file=51810932
- 22. Madugalle TMSSB, Jayasundara DMCS, Jayawardane IA. Figshare. [Online]. 2025. [cited 2025 Jan 21. ]. Available from: https://figshare.com/articles/dataset/Data_set_primi_xlsx/28243115?file=51810941
- 23. Mullin PM, House M, Paul RH, Wing DA. A comparison of vaginally administered misoprostol with extra-amniotic saline solution infusion for cervical ripening and labor induction. Am J Obstet Gynecol. 2002;187(4):847–52. pmid:12388962
- 24. Ghanaei MM, Sharami H, Asgari A. Labor induction in nulliparous women. J Turkish-German Gynecol Assoc. 2009;10:71–5.
- 25. Karjane NW, Brock EL, Walsh SW. Induction of labor using a foley balloon, with and without extra-amniotic saline infusion. Obstet Gynecol. 2006;107(2 Pt 1):234–9. pmid:16449106
- 26. Putnam K, Magann EF, Doherty DA, Poole AT, Magann MI, Warner WB, et al. Randomized clinical trial evaluating the frequency of membrane sweeping with an unfavorable cervix at 39 weeks. Int J Womens Health. 2011;3:287–94. pmid:21892340
- 27. Magann EF, Chauhan SP, McNamara MF, Bass JD, Estes CM, Morrison JC. Membrane sweeping versus dinoprostone vaginal insert in the management of pregnancies beyond 41 weeks with an unfavorable cervix. J Perinatol. 1999;19(2):88–91. pmid:10642965