According to the American College of Obstetricians and Gynaecologists (ACOG 2013), Term pregnancy which is defined as pregnancy from 37 completed weeks to 41 weeks + 6 days gestation can be sub-divided into 03 groups: Early term; is pregnancy from 37 completed weeks to 38 weeks + 6 days gestation, Full term; is pregnancy from 39 completed weeks to 40 weeks + 6 days gestation and Late term; is pregnancy from 41 completed weeks to 41 weeks + 6 days gestation. Post-term pregnancy is defined as a pregnancy that continues beyond 42 weeks (294 days) from the day of the last menstrual period (LMP) or 14 days beyond the best obstetric estimate of the date of delivery [1]. Stripping of foetal membranes is one of the oldest but least understood methods to prevent post-maturity [2]. Stripping of the membranes entails the digital separation of the amniotic-chorionic membranes from the lower uterine segment. It causes an increase in prostaglandin metabolites in the maternal circulation as well as local prostaglandin production [3]-[6]. Membrane stripping is cheap, easy to use, and its safety has been confirmed in almost all studies [2][7][8]. It has been used either to induce labour 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 stripping [2].

The prevalence of post-term pregnancy depends on the particular patient population, including factors such 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 affect the overall prevalence of prolonged pregnancy, particularly as induction of labour before 42 weeks of gestation has increased in recent years [1]. In the United States in 2005, the prevalence of post-term pregnancy was 6% [9]. This was lower than the 10% observed in 1998 [10]. In Wales, the prevalence dropped from 4.6% in 1990 to 2.8% in 1996 [11]. The decline in the prevalence of post-term pregnancy was associated with increasing rates of induction of labour [1][12]. In Sub-Saharan Africa, including Cameroon, the prevalence of post-term pregnancy is quoted as 8% - 10% of all pregnancies [13]. However, it has been shown that accurate dating in early pregnancy and elective induction of labour at 41 weeks of gestation can reduce the prevalence to as low as 1% [1][5][14][15]. Our study tries to evaluate the effectiveness and safety of foetal membranes stripping at 40 completed weeks of gestation on the prevalence of late-term pregnancy in the Cameroonian context, with goal to inform clinicians and policy makers.

Stripping of foetal membranes is one method whose efficacy has mainly been assessed as a method of inducing labour. The procedure is safe, easy to perform, and inexpensive. In this study, membrane stripping was used to evaluate its effectiveness in preventing late-term pregnancies, in low‑risk pregnant women.

All pregnant women with closed cervices were excluded from the study firstly because an open cervix is a requirement to conduct membranes stripping, given the fact that you have go through the cervix with the examining gloves to get access to the foetal membranes. Secondly cervical massage which as an alternative to membranes stripping 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 stripping of the membranes [5][16]. However, this could still be a subject for further studies, given the fact that a closed or an open cervix at term is a reflection of the dynamic nature of the physiological changes of pregnancy and labour onset [17]. The implication is that a woman with an open cervix at term will likely benefit from an objective method of preventing post term pregnancy, rather than a subjective method being used on a closed cervix.

During the conduct of this study, there were no dropouts of participants given the short interval from eventual delivery of less than two weeks. This could also be attributed to the fact that participants were highly motivated more so that their pregnancies were already beyond their EDDs. The exposed group women 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” as they were all reminded the night before their hospital visits. However, this was not the case in similar studies conducted elsewhere. The study done in Ile‑Ife, Nigeria [2], had nine participants that were lost to follow‑up and another study done in Istanbul, Türkiye [5] 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 [18], 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 membranes stripping, which in their study was done twice weekly. In our study, this was not the case as membrane stripping was done once at 40 completed weeks of gestation for the exposed group.

Stripping of foetal membranes effectively reduced the incidence of late-term pregnancies. The incidence of delivery at late-term gestation after induction of labour was significantly lower in the membranes stripping group compared with the unexposed group (12% vs. 43%; P < 0.001). The proportion of those that had spontaneous labour in the exposed group was 171 (88%) compared to the unexposed group that had 111 (57%). This was statistically significant with P < 0.001 (Table 5). Several studies have shown that fewer women eventually need induction for pregnancy beyond 41 weeks if membrane stripping is performed during antenatal clinic [2][19]-[21]. All the women who had induction of labour as from 41 completed weeks according to our departmental protocol had late-term pregnancy. Likewise, in the Ile‑Ife study [2], one of their primary outcome measures was the proportion of women whose gestation exceeded 41 weeks. Therefore, they carried out induction of labour at 41‑week gestation with indication being late-term pregnancy. Studies in Saudi Arabia and in Washington DC also carried out induction of labour at 41‑week gestation with indication being late-term pregnancy [18][21].

However, in most of these studies, the absolute proportion of women that ended up with induction of labour for late-term gestation were lower in both the membranes stripping group and the unexposed group compared to the values from our study. The Ile‑Ife study showed that 3% in the membranes stripping group versus 16% in the unexposed group had induction of labour. 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 labour was considered while our study recruited at 40 completed weeks of gestation. Furthermore, there may be a possibility that some of their participants could have experienced spontaneous onset of labour on or before their EDD with or without stripping 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 completed weeks of gestation might be a fairer representation of the proportion of women likely to experience late-term pregnancy and subsequently induction of labour.

There was also a significant reduction in the recruitment to spontaneous labour-onset mean-time interval in our study, (2.51 ± 0.98 in exposed group vs. 4.33 ± 1.18 in unexposed group, P < 0.001). Similar observation was made by studies in Ile-Ife Nigeria [2], Abuja Nigeria [22] and Washington DC [18]. These observers found a significant lower mean-time interval from recruitment to spontaneous labour-onset among the stripping group.

It was observed that the Bishop’s scores at recruitment were slightly different between the two groups with slightly higher scores in the stripping group compared with the unexposed group, although this was not statistically significant (P = 0.032). 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’s scores at recruitment showed no significant difference between the two groups (P = 0.032), this was not the case when the Bishop’s scores between the two groups among those who had induction of labour were compared. The pre-induction Bishop’s scores assessment at admission revealed a statistically significant difference between the two groups (P < 0.001) with significantly higher Bishop’s scores on admission in the membrane stripping group compared with the unexposed group. Similar findings were observed by most researchers [2][8][16][22].

Nineteen women in the membrane stripping group and thirty-six women in the unexposed group had caesarean delivery (9.8% vs. 19%, P = 0.013). This difference was statistically not significant, which was also the discovery made in Abuja Nigeria study [22]. However, a similar study in USA observed a significantly decreased caesarean delivery rate with membrane stripping but due to the limitation of their sample size, they remarked that a larger trial was needed to confirm this finding. Another similar study in England, however, observed an increased risk of caesarean delivery in the stripping group, but the difference did not reach a statistical significance. The effect of membrane stripping on caesarean delivery rate remains inconclusive for now and must await the result of larger trials and more reviews [23][24].

In our study, stripping of membranes did not significantly alter the mode of vaginal delivery (90.2% vs. 81%; P = 0.013). Most studies made similar observations [5][22]. No significant differences were observed in maternal and foetal complications in this study. The safety of stripping of membranes is confirmed in almost all studies [2][5]-[8][19]. This was the case in our study where it was observed that neonatal outcome including birth weight, Apgar Scores at 5 min, and admission into neonatal ICU were similar between the two groups. Apgar Score <7 at 5 min was considered birth asphyxia. Several studies [2][21][22] also adopted Apgar Score <7 as birth asphyxia. It was also observed that participants expressed more satisfaction with birth process despite slightly more initial discomfort after stripping.

Stripping of foetal membranes may appear to effectively reduce the incidence of late-term pregnancies, by lowering the mean-time interval from recruitment to spontaneous labour-onset, and also improve the pre-induction Bishop score. The procedure appears safe as it doesn’t increase the risk of maternal and neonatal adverse outcomes.

This article is issued from the Dissertation submitted in partial fulfillment of the requirements for the award of a specialization diploma (DES) in Obstetrics and Gynaecology of Dr Enow Colbert Bisong, MD. We are grateful to all specialists, general practitioners, house officers and nurses involved in the care of study participants. All of this was done under the supervision of Professor MBU Robinson ENOW.