|Year : 2019 | Volume
| Issue : 1 | Page : 15-21
Effectiveness of sweeping of membranes in reducing the incidence of elective induction of labor for postdate pregnancies
MG Nyamzi1, DA Isah2, RA Offiong1, AY Isah2
1 Department of Obstetrics and Gynaecology, University of Abuja Teaching Hospital, Abuja, Nigeria
2 Department of Obstetrics and Gynaecology, University of Abuja Teaching Hospital; Department of Obstetrics and Gynaecology, College of Health Sciences, University of Abuja, Abuja, Nigeria
|Date of Web Publication||15-Oct-2019|
Dr. D A Isah
Department of Obstetrics and Gynaecology, University of Abuja Teaching Hospital/ College of Health Sciences, University of Abuja, Abuja
Source of Support: None, Conflict of Interest: None
Introduction: Prolonged pregnancy is a high-risk pregnancy that is associated with increased maternal morbidity and increased perinatal morbidity and mortality. Objectives: The objective was to evaluate the effectiveness of sweeping of the fetal membranes to reduce the incidence of elective induction of labor for postdate pregnancy and to compare pregnancy outcome among women who had sweeping of membranes at 40 weeks with those who did not have sweeping of membranes. Subjects and Methods: This was a randomized, controlled study conducted from September 2017 to June 2018. One hundred and ninety-four consenting participants with no contraindication to vaginal delivery were randomized into two groups, those who had membrane sweeping at 40–41 weeks' gestation and a control group who had vaginal examination to assess Bishop score only at recruitment. Participants were followed up to delivery. Results: Sweeping of membranes effectively reduced the incidence of elective induction of labor. The proportion of those that had spontaneous labor in the treatment group was 85 (87.6%) compared to the control group that had 67 (62.9%). This was statistically significant with P < 0.001. The incidence of induction of labor was significantly lower in the membrane sweeping group compared with the control group (12.4% vs. 37.1%; P < 0.001). There was a significant higher mean time interval from recruitment to admission (recruitment admission interval) among the control group (5.76 ± 2.75 days) compared with those that had membrane sweeping (3.35 ± 2.55; P < 0.001). Conclusion: Sweeping of the membranes appears an effective and safe procedure in reducing the incidence of elective induction of labor and duration of pregnancy at term in low-risk population.
Keywords: Elective induction, incidence, outcome, postdate pregnancy
|How to cite this article:|
Nyamzi M G, Isah D A, Offiong R A, Isah A Y. Effectiveness of sweeping of membranes in reducing the incidence of elective induction of labor for postdate pregnancies. Arch Med Surg 2019;4:15-21
|How to cite this URL:|
Nyamzi M G, Isah D A, Offiong R A, Isah A Y. Effectiveness of sweeping of membranes in reducing the incidence of elective induction of labor for postdate pregnancies. Arch Med Surg [serial online] 2019 [cited 2023 Jun 1];4:15-21. Available from: https://www.archms.org/text.asp?2019/4/1/15/269234
| Introduction|| |
Prolonged pregnancy is defined as a pregnancy that continues from 42 weeks (294 days) and above from the day of the last menstrual period (LMP) or 14 days beyond the best obstetric estimate of the date of delivery.
Sweeping of fetal membranes is one of the oldest but least understood methods to prevent postmaturity. Sweeping of the membranes entails the digital separation of the amniochorionic membranes from the lower uterine segment. It causes an increase in prostaglandin metabolites in the maternal circulation as well as local prostaglandin production.,,,
Membrane sweeping is cheap, easy to use, and its safety has been confirmed in almost all studies.,, It has been used either to induce labor or to shorten the length of pregnancy. However, some of these studies were not randomized and had selection bias, and as a result, there is still controversy on the clinical utility of membrane sweeping.
The prevalence of prolonged pregnancy depends on the particular patient population, including such factors as the percentage of primigravid women, the prevalence of obesity, proportion of women with pregnancy complications, the prevalence of ultrasound assessment of gestational age, and the frequency of spontaneous preterm birth. Local practice pattern such as the rates of scheduled cesarean delivery and routine labor induction also will affect the overall prevalence of prolonged pregnancy, particularly as induction of labor before 42 weeks of gestation has increased in recent years. In the United States in 2005, the prevalence of postterm pregnancy was 6%. This was lower than the 10% observed in 1998.
In Wales, the prevalence dropped from 4.6% in 1990 to 2.8% in 1996. The decline in the prevalence of prolonged pregnancy was associated with increasing rates of induction of labor.,
In Nigeria, the incidence of prolonged pregnancy is quoted as 8%–10% of all pregnancies. However, it has been shown that accurate dating in early pregnancy and elective induction of labor at 41 weeks of gestation can reduce the incidence to as low as 1%.,,, The incidence of intraocular lens (IOL) worldwide is 3%–30%., The incidence of IOL in the UK is 19.5%. Hospital-specific rates of IOL from literature reported the following incidences in Nigeria: University of Abuja Teaching Hospital was 13%, Enugu was 16.3%, and Ile-Ife was 15.7%.
In a recent study, it was demonstrated that not only did first-trimester ultrasound dating lead to lower rates of postterm pregnancy and pregnancy beyond 41 weeks of gestation being diagnosed but also better dating reveals a greater difference in the rate of perinatal complications.,
Perinatal mortality at 42 weeks of gestation is twice that at 40 weeks and increases 4-fold at 43 weeks and 5–7-fold at 44 weeks. A number of key morbidities are greater in infants born to postdate pregnancies, including meconium and meconium aspiration, neonatal acidemia, low Apgar scores, macrosomia, and in turn birth injury. Other complications associated with macrosomia include prolonged labor, cephalopelvic disproportion, and shoulder dystocia with resultant risks of orthopedic or neurologic injury. Approximately 20% of prolonged pregnancy fetuses have “fetal dysmaturity (postmaturity) syndrome,” which describes infants with characteristics of chronic intrauterine growth restriction from uteroplacental insufficiency. The pregnancies are at increased risk of umbilical cord compression due to oligohydramnios, nonreassuring fetal antepartum, or intrapartum assessment. They are also at increased risk of short-term neonatal complications such as hypoglycemia, seizures, and respiratory insufficiency. Prolonged pregnancy is also an independent risk factor for neonatal anencephaly  and for death in the 1st year of life.
The maternal risks of prolonged pregnancy are often underappreciated. These include an increase in labor dystocia (9%–12% vs. 2%–7% at term), an increase in severe perineal injury related to macrosomia (3.3% vs. 2.6% at term) and operative vaginal delivery and a doubling in the rate of cesarean delivery (14% vs. 7% at term). The latter is associated with higher risks of complications such as endometritis, hemorrhage, and thromboembolic disease. In addition, the emotional impact (anxiety and frustration) of carrying a pregnancy 1–2 weeks beyond the estimated date of delivery (EDD).,
The justification for this study emanates from the several studies of the effectiveness of membrane sweeping that has produced inconsistent results. A recent Cochrane review reported that the routine use of membrane sweeping from 38 weeks onward does not seem to have clinically important benefits. de Miranda et al. noted that the Cochrane review included studies with relatively small sizes and heterogeneity between the trial results' outcome.
Furthermore, the increased perinatal and maternal morbidity and mortality associated with elective induction of labor for postdate pregnancy for the prevention of prolonged pregnancy is the rationale for this study, and second, such a study was yet to be carried out in this institution. Membrane sweeping is cheap, easy to use, minimally invasive, and also safe.
| Subjects and Methods|| |
This was a randomized controlled trial at the Department of Obstetrics and Gynaecology, University of Abuja Teaching Hospital, Abuja. The hospital is located in Gwagwalada Area Council of Nigeria's federal capital territory, whose geographical coordinates are 8° 56' 29” north and 7° 5' 31” east. The facility provides health-care services to the inhabitants of Abuja and neighboring states of Niger, Kogi, and Nasarawa.
The study was conducted between September 2017 and June 2018 after obtaining the written permission from the hospital's human research and ethical committee and the college.
The study population was all pregnant women at 40–41 weeks plus 0 day of gestation receiving antenatal care, with no contraindication to vaginal delivery and whose pregnancy was adjudged as low-risk pregnancy (singleton fetus, longitudinal lie, and cephalic presentation) were recruited until the sample size was obtained. The minimum sample size in each arm was calculated using the formula n = 2n (Machin and Campbell 1978), where n was the required minimum sample size in each of the study arm from the formula and with attrition rate of 10%; this gave a sample size of 97.
Zα= The level of significance at 5% (0.05) = 1.96
Zβ= Correspond to the statistical power of 90% (0.90)
p0 = Response in the intervention group (from a study done in Ile-Ife) = 0.97
p1 = Expected response in this study = 0.82
Thus, = 87.68
Given an attrition rate of 10%,
Then sample size =
Anticipated response rate = 0.90
Each trial group was be allocated 97 participants.
The minimum sample size altogether (n) = 194
Therefore, a total sample size of 194 was gotten for the study.
All pregnant women with high-risk pregnancy such as multiple gestations, breech presentation, transverse lie, unstable medical conditions in pregnancy, previous uterine scar, placenta previa, contracted pelvis, all pregnant women with indication for elective delivery before 40 weeks, all pregnant women with contraindication to vaginal delivery, all pregnant women with closed cervical Os at 40 weeks to 41 weeks and 0 day, all pregnant women who were unsure of their last normal menstrual period and did not have an ultrasound scan dating before 16 weeks of gestation, and no consenting patients were excluded from the study.
All prospective participants were educated about the study during the routine antenatal health talk. The gestational age was ascertained using a sure/reliable LMP and/or an ultrasound scan dating done before 16 weeks of gestation. Individual counseling was done at 39-week gestation in anticipation, and recruitment was done at 40–41 weeks plus 0 day. An ultrasound scan was then done to estimate the fetal weight and ascertain placenta location.
Eligible consenting participants were randomized into two groups, intervention group (those for Bishop scoring and membrane sweeping) and control group (those for vaginal examination for Bishop scoring without membrane sweeping), after signing an informed consent. Randomization was performed using a computer-generated list by means of sequentially numbered, opaque, sealed envelopes indicating “intervention” or “control.” While the first group had Bishop scoring and membrane sweeping, the second group, that is, control group had Bishop scoring only. Those chosen as control group were pregnant women at 40–41 weeks plus 0 day of gestation receiving antenatal care, with no contraindication to vaginal delivery and whose pregnancy was adjudged as low-risk pregnancy and eligible. Three research assistants, obstetrics, and gynecological were trained to assist in this study. Their duty was to identify and counsel candidates eligible for the study from the antenatal clinic and also to notify the principal investigator for further counseling, signing of informed consent form, and recruitment.
Personal identification numbers were allocated to the participants in addition to documenting their hospital numbers and telephone numbers for easy tracing and appointment.
In the antenatal clinic, under aseptic conditions and with patients in dorsal position, a vaginal examination was carried out on all the individuals by the principal investigator only to eliminate subjective error. The middle and index fingers of the gloved hand were passed into the vagina; the position, consistency, length in centimeters, os dilatation in centimeters of the cervix, and the station of the presenting part were determined [Table 1]; and the Bishop scores were recorded for all patients. However, for the intervention group, after assessment of the Bishop score with the examining digits still in the vagina, the middle finger was passed through the cervical os into the lower portion of the lower uterine segment. Sweeping of membranes was then performed by separating approximately 2–3 cm of chorionic membranes from the lower uterine segment using two circumferential movements of the middle finger. Sweeping of membranes was done once.
The participants were observed for at least 30 min in the antenatal clinic after membrane sweeping, after which they were discharged home with no complications and were advised to come for twice weekly ultrasound scan, cardiotocography/biophysical profile and were also informed about the possibility of passage of “show.” They were instructed to come to the labor ward if they experience decreased fetal movement, rupture of the membranes, excessive vaginal bleeding, or onset of labor. Clinical data for each participant were collected and recorded on a datasheet for the analysis.
The primary outcome was to determine the proportion of pregnancy reaching an estimated gestational age of 41 weeks and 3 days between the treatment and control groups. The secondary outcome was to determine the time interval between sweeping of membranes and onset of labor, whether or not there was an improvement in Bishop score in both groups from recruitment to admission for those women who did not go into labor at 41 weeks and 3 days and to determine pregnancy outcome between the two groups. Intervention in both groups occurred if the study participants did not go into spontaneous labor before 41 weeks and 3 days; elective induction is done.
Data were analyzed using the Statistical Package for Social Sciences (SPSS) package version 22.0, August 2013 (IBM, Armonk, NY, United States of America). The data are presented using simple frequency table. Statistical analysis of categorical data was performed by Chi-square test.
| Results|| |
A total of 194 women were randomized and divided into two groups as follows: treatment and control groups. Ninety-seven women each were randomized into each of the two groups; those that had membrane sweeping at 40–41 weeks' and 0-day gestation and a control group who had vaginal examination to assess Bishop score only. The demographic characteristics and Bishop score at the onset of the study were comparable between the two groups [Table 1].
Sweeping of membranes effectively reduced the incidence of elective induction of labor. The proportion of those that had spontaneous labor in the treatment group was 85 (87.6%) compared to the control group that had 67 (62.9%). This was statistically significant with P <0. 001. The incidence of induction of labor was significantly lower in the membrane sweeping group compared with the control group (12.4% vs. 37.1%; P < 0.001). There was a significant higher mean time interval from recruitment to admission (recruitment admission interval) among the control group (5.76 ± 2.75 days) compared with those that had membrane sweeping (3.35 ± 2.55; P < 0.001) [Table 2].
|Table 2: Demographic characteristics were comparable between the two groups|
Click here to view
The successful rate of vaginal delivery has no significant difference between the two groups [Table 2]. Although cesarean delivery occurred less frequently in the membrane sweeping group, the difference was not statistically significant (P = 0.138).
The Bishop scores at recruitment for those who finally had induction of labor at 41 weeks and 3-day gestation showed no significant difference between the two groups (P = 0.851) [Table 3]. However, the preinduction Bishop scores at admission revealed a statistical significant difference between the two groups (P < 0.001) [Table 3].
|Table 3: Comparing Bishop scores between the two groups among those who had induction of labor|
Click here to view
Overall, both the maternal and fetal complications were similar between the two groups [Table 4] and [Table 5]. Although maternal discomfort during vaginal examinations was slightly more frequent in the membrane sweeping group (32.0% vs. 27.8%; P = 0.815) [Table 4], the discomfort was not severe enough to require medication in any of the women and was acceptable to the patients. There were no cases of inadvertent spontaneous rupture of membrane occurring in any of the group. Prelabor rupture of membrane occurred with equal frequency in both groups (8.2% vs. 8.2%; P = 0.602) [Table 4].
Neonatal outcomes were similar in both groups [Table 5]. Three neonates in the sweeping of membranes group and four in the control group had Apgar score of <7 at 5 min (P = 0.710). There were four special care baby unit (SCBU) admissions in the membrane sweeping group and five in the control group (P = 0.506). There were no neonatal deaths in both study groups.
| Discussion|| |
Sweeping of membranes is one method that has been used to prevent elective induction of labor, although the efficacy of the procedure has mainly been assessed as a method of inducing labor. The procedure is safe, easy to perform, and inexpensive. In this study, membrane sweeping was used to prevent elective induction of labor in low-risk pregnant women.
All pregnant women with closed cervices were excluded from the study because cervical massage as an alternative to membrane sweeping in the presence of a closed cervix seems to be highly subjective, although there have been several studies that adopted cervical massage as an alternative to sweeping of the membranes when the cervix is closed, for example, study by Yildirim et al. and Nasim et al. However, this could still be a subject for further trials.
During the conduct of this study, there were no dropouts of participants, perhaps this may be attributed to the fact that participants were highly motivated more so that their pregnancies were already beyond their EDDs. The individuals were, therefore, curious and readily welcomed the intervention. A dedicated telephone number given to all participants in addition to collecting their telephone numbers for prompt communication might also have contributed to the “no dropout.”
However, this was not the case in similar studies conducted elsewhere. The study done in Ile-Ife, Nigeria, by Dare and Oboro  had nine participants that were lost to follow-up and another study done in Istanbul, Turkey by Yildirim et al. had five “drop-out” of participants; perhaps this was so in these studies because both studies recruited women at term that were yet to reach their EDDs (i.e., at 38-week gestation). This earlier recruitment might have contributed to some of the participants feeling that perhaps there was no danger to their pregnancies and that there was still more time to go and eventually they were lost to follow-up. In another study done in Washington DC by Putnam et al., there were five dropouts; four of the women dropped out because of the desire to be induced before 41 weeks of gestation, which was their endpoint. The fifth woman dropped out due to the discomfort of membrane sweeping, which in their study was done twice weekly. In this study, this was not the case; membrane sweeping was done once at 40 weeks and above gestation.
Sweeping of membranes effectively reduced the incidence of elective induction of labor. The proportion of those that had spontaneous labor in the treatment group was 85 (87.6%) compared to the control group that had 67 (62.9%). This was statistically significant with P < 0.001. The incidence of induction of labor was significantly lower in the membrane sweeping group compared with the control group (12.4% vs. 37.1%; P < 0.001). There was a significant higher mean time interval from recruitment to admission (recruitment admission interval) among the control group (5.76 ± 2.75 days) compared with those that had membrane sweeping (3.35 ± 2.55; P < 0.001) [Table 2]. Several studies have shown that fewer women eventually need induction for pregnancy beyond 41 weeks if membrane sweeping is performed antenatally.,,, All the women who had induction of labor at 41 weeks and 3 days according to our departmental protocol had postdate pregnancy. Likewise, in the Ile-Ife study, one of their primary outcome measures was the proportion of women whose gestation exceeded 41 weeks. Therefore, they carry out induction of labor at 41-week gestation, indication being postdate pregnancy, probably this was the policy in their department. Yildirim et al. in Istanbul, Turkey and Putnam et al. in Washington DC both also carry out induction of labor at 41-week gestation, indication being postdate pregnancy.
There was also a significant reduction in the recruitment admission interval, that is, interval from recruitment to labor onset (3.35 ± 2.55 vs. 5.76 ± 2.75, P < 0.001). Similar observation was made by Dare et al., Yildirim et al., and Putnam et al. These observers found a lower incidence of prolonged (41 weeks or greater) pregnancies in the sweeping group. However, in most of these studies, the absolute proportion of women that ended up with induction of labor were lower in both the membrane sweeping group and the control group compared to the values from this study. The Ile-Ife study showed that 3% in the membrane sweeping group versus 16% in the control group had induction of labor. These lower percentages may be likely due to the fact that recruitment was early (at 38-week gestation), and hence, participants had longer period to go before induction of labor was considered. This study recruited at 40 weeks and above gestation. Furthermore, there may be a possibility that some of their participants could have experienced spontaneous onset of labor on or before their EDD with or without sweeping of the membranes. In other words, there could be a possibility that recruitment at 38 weeks of gestation might not be a true representation of the proportion of women likely to go beyond their EDDs. While, on the other hand, recruitment at 40 weeks and above gestation might be a fairer representation of the proportion of women likely to experience prolonged pregnancy and subsequently induction of labor.
The time from hospital admission to time of delivery was not different in the two groups. However, there was a shorter duration from recruitment to hospital admission and a significantly higher Bishop's score on admission in the membrane sweeping group compared with the control group. Similar findings were observed by most researchers.,,
It was observed that the Bishop's scores at recruitment were slightly different between the two groups with slightly higher scores in the sweeping group compared with the control group, although this was not statistically significant. This slight difference in Bishop's scores at recruitment between the two groups could have been minimized by stratification of the initial Bishop's scores and the parity. Even though the overall Bishop scores at recruitment and at admission showed no significant difference between the two groups, this was not the case when the Bishop scores between the two groups among those who had induction of labor were compared; there was no statistically significant difference between the groups at recruitment (P = 0.851); however, the preinduction Bishop scores assessment at admission revealed a statistically significant difference between the two groups (P < 0.001). Nasim et al. made similar observations.
Ten of the sweeping group and fourteen of the control group had cesarean delivery (10.3% vs. 14.4%, P = 0.441). This difference was statistically not significant, which was also the discovery made by Dare et al. However, Averil et al. observed a significantly decreased cesarean delivery rate with membrane sweeping; due to the limitation of their sample size, they remarked that a larger trial was needed to confirm this finding. Allott and Palmer, however, observed an increased risk of cesarean delivery in the sweeping group, but the difference did not reach a statistical significance. The effect of membrane sweeping on cesarean delivery rate remains inconclusive for now and must await the result of larger and more trials and reviews.
In the present analysis, sweeping of membranes did not significantly alter the mode of delivery (89.7% vs. 82.5%; P = 0.138). Most studies made similar observations., No significant differences were observed in maternal and fetal complications in this study (P = 0.815). The safety of sweepings of membranes is confirmed in almost all studies;,,,,, this was the case in this study where it was observed that neonatal outcome including birth weight, Apgar Scores at 5 min, and admission into SCBU were similar between the two groups. Apgar Score <7 at 5 min was considered birth asphyxia. More so, our SCBU adopts the same. Several studies , also adopted Apgar Score <7 as birth asphyxia. It also observed that participants expressed more satisfaction with birth process despite slightly more initial discomfort after sweeping.
| Conclusion|| |
Sweeping of membranes is an effective and safe procedure in reducing the incidence of elective induction of labor and the duration of term pregnancy. Sweeping of membranes at term seems to improve the preinduction Bishop score. There is no evidence that sweeping of membranes increases the risk of maternal and neonatal adverse outcomes.
Sweeping of membranes may have a role in modern obstetric practice and could be considered a reasonable option in reducing the rate of elective induction of labor and subsequently preventing prolonged pregnancy.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Caughey AB, Snegovskikh VV, Norwitz ER. Postterm pregnancy: How can we improve outcomes? Obstet Gynecol Surv 2008;63:715-24.
Dare FO, Oboro VO. The role of membrane stripping in prevention of post-term pregnancy: A randomised clinical trial in Ile-Lfe, Nigeria. J Obstet Gynaecol 2002;22:283-6.
Mitchell MD, Flint AP, Bibby J, Brunt J, Arnold JM, Anderson AB, et al.
Rapid increases in plasma prostaglandin concentrations after vaginal examination and amniotomy. Br Med J 1977;2:1183-5.
Keirse MJ, Thiery M, Parewijck W, Mitchell MD. Chronic stimulation of uterine prostaglandin synthesis during cervical ripening before the onset of labor. Prostaglandins 1983;25:671-82.
Yildirim G, Gungorduk K, Karadag OI, Aslan H, Turhan E, Ceylan Y. Membrane sweeping to induced labour in low-risk patients at term pregnancy: A randomised controlled trial. J Matern Fetal Neonatal Med 2010;23:681-7.
Royal College of Obstetricians and Gynaecologists. Induction of labour. In: Evidence – Based Clinical Guideline Number 9. London: RCOG Clinical Support Unit; 2008. p. 59-62.
Berghella V, Rogers RA, Lescale K. Stripping of membranes as a safe method to reduce prolonged pregnancies. Obstet Gynecol 1996;87:927-31.
Magann EF, Chauhan SP, Nevils BG, McNamara MF, Kinsella MJ, Morrison JC. Management of pregnancies beyond forty-one weeks' gestation with an unfavorable cervix. Am J Obstet Gynecol 1998;178:1279-87.
Martin JA, Hamilton BE, Sutton PD, Ventura SJ, Menacker F, Kirmeyer S, et al.
Births: Final data for 2005. Natl Vital Stat Rep 2007;56:1-103.
Ventura SJ, Martin JA, Curtin SC, Mathews TJ, Park MM. Births: Final data for 1998. Natl Vital Stat Rep 2000;48:1-100.
Roberts CL, Taylor L, Henderson-Smart D. Trends in births at and beyond term: Evidence of a change? Br J Obstet Gynaecol 1999;106:937-42.
Ekele BA, Oyetunji JA. Induction of labour at Usmanu Danfodiyo university teaching hospital, Sokoto. Trop J Obstet Gynaecol 2002;19:74-7.
Emuveyan EE. Prolonged pregnancy. In: Kwawukume EY, Emuveyan EE, editors. Comprehensive Obstetrics in the Tropics. 1st
ed. Accra, Ghana: Asente and Hittscher 2002. p. 135-9.
Ekele BA, Nnadi DC, Gana MA, Shehu CE, Ahmed Y, Nwobodo EI, et al.
Misoprostol use for cervical ripening and induction of labour in a Nigerian teaching hospital. Niger J Clin Pract 2007;10:234-7.
Goeree R, Hannah M, Hewson S. Cost-effectiveness of induction of labour versus serial antenatal monitoring in the Canadian multicentre postterm pregnancy trial. CMAJ 1995;152:1445-50.
Ande AB, Orhue AA. Induction of labour. In: Clinical Obstetrics. Okpere E, editors. 1st
ed. Benin city: Uniben Press; 2003. p. 266-73.
Orhue AA. Review of induction of labour. Trop J Obstet Gynaecol 1997;14:1-14.
Department of Health. NHS Maternity Statistics, England: 1989-90 to 1994-5, Statistics Bulletin 1997/8. London: Department of Health; 1997. p. 1-44.
Onafowokan O, Kailani S, Offiong RA, Kwaghe GV, Akaba G, Otubu JA. Outcome of labour induced with misoprostol. Trop J Obstet Gynaecol 2006;23:S16.
Chigbo CO, Ezeome IV, Okezie AO, Oyefara B. Induction of labour on request in a resource-poor setting. Int J Obstet Gynaecol 2007;98:208-11.
Loto OM, Ayuba II, Adebara IO, Ikuomola AA, Onwudiegwu U. Randomised clinical trial of misoprostol and oxytocine for induction of labour. Nepal J Obstet Gynaecol 2010;5:44-8.
Caughey AB, Nicholson JM, Washington AE. First versus second trimester ultrasound: The effect on pregnancy dating and perinatal outcomes. Am J Obstet Gynaecol 2008;198:703. e1-5.
Cotzias CS, Paterson-Brown S, Fisk NM. Prospective risk of unexplained stillbirth in singleton pregnancies at term: Population based analysis. BMJ 1999;319:287-8.
Badawi N, Kurinczuk JJ, Keogh JM, Alessandri LM, O'Sullivan F, Burton PR, et al.
Intrapartum risk factors for newborn encephalopathy: The western Australian case-control study. BMJ 1998;317:1554-8.
Rand L, Robinson JN, Economy KE, Norwitz ER. Post-term induction of labor revisited. Obstet Gynecol 2000;96:779-83.
Alexander JM, MCIntire DD, Leveno KJ. Prolonged pregnancy: Induction of labor and cesarean births. Obstet Gynecol 2001;97:911-5.
Boulvain M, Stan C, Irion O. Membrane sweeping for induction of labour. Cochrane Database Syst Rev 2005;(1):CD000451.
de Miranda E, van der Bom JG, Bonsel GJ, Bleker OP, Rosendaal FR. Membrane sweeping and prevention of post-term pregnancy in low-risk pregnancies: A randomised controlled trial. BJOG 2006;113:402-8.
Nasim A, Tahir R, Nusrat U. Is membrane sweeping appropriate in modern obstetrics for induction of labour in post-date pregnancies? Pak J Surg 2011;27:223-8.
Putnam K, Magann EF, Doherty DA, Poole AT, Magann MI, Warner WB. Randomized clinical trial evaluating the frequency of membrane sweeping with an unfavorable cervix at 39 weeks. Int J Womens Health 2011;3:287-94.
Mozurkewich EL, Chilimigras JL, Berman DR, Perni UC, Romero VC, King VJ, et al.
Methods of induction of labour: A systematic review. BMC Pregnancy Childbirth 2011;11:84.
Averill KA, Scardo JA, Chauhan SP. Weekly membrane stripping to decrease the incidence of post-term pregnancy: A randomized clinical trial. Obstet Gynaecol 1999;93:478.
Allott HA, Palmer CR. Sweeping the membranes: A valid procedure in stimulating the onset of labour? Br J Obstet Gynaecol 1993;100:898-903.
Adcock LM, Papile L. Perinatal asphyxia. In: Cloherty JP, Eichenwald EC, Stark AR, editors. Manual of Neonatal Care. 6th ed. Philadelphia: Lippincott Williams and Wilkins; 2008. p. 508-28.
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]