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May 2005, Volume 55, Issue 5

Original Article

Induction of Labour with Oral Misoprostol for Prelabour Rupture of Membranes at term

Abstract

Objective: To study the efficacy, safety and maternal satisfaction of oral misoprostol for induction of labour in patients with prelabour rupture of membrane at term (PROM).

Methods: Pregnant women with singleton pregnancy at term with cephalic presentation with prelabour rupture of membranes having no other obstetric and maternal contraindications for induction of labour, were included in the study. Patients were given 50ugm of oral misoprostol at six hourly intervals for a total of three doses or until labour was established.

Results: Of the 104 patients included in the study, 28 (26.9%) were primigraivda and 72.1% were multigravida. Induction delivery internal was shorter in multigravida and longer in primigraivda. Patients with Bishop score of less than 5 had a longer induction delivery interval as compared to patients with Bishop score more than 5. Significant side effects included nausea and vomiting in 68 patients (65.3%). Vaginal delivery was achieved in 80.7% with Cesarean section in 19.2% of patients. Neonatal outcome was good with no stillbirths and only two neonatal deaths. A large number, 98 (94.2%) of women were satisfied with induction of labour with oral misoprostol in PROM.

Conclusion: Active management with oral misoprostol resulted in more women going into labour and delivering within 24 hours of PROM with no significant maternal and neonatal complications (JPMA
55:180;2005).

Introduction

Prelabour rupture of membranes at term is a common occurrence with an incidence of 8%. 1 Its management is still a matter of debate, and varies from center to center. Active induction if labour soon after prelabour rupture of membranes has resulted in a lower risk of maternal and fetal sepsis 2-5 as compared to conservative management.

Women with active management had a shorter interval till delivery and active management was preferred by the patients. 6

Misoprostol is a unique prostaglandin E1 analogue, which is rapidly absorbed orally. Tablets marketed for anti-inflammatory drug-induced gastric ulceration, are stable and cheap. Its effect on myometrium is mediated by binding to prostanoid receptors in the myometrium. The drug does not require refrigeration prior to its use. It is available in blister packing. 7 These features make it ideal for use in third world countries.

In most trials vaginal route has been chosen, presumably because this route has been most successful for other prostaglandins and because misoprostol has a far longer half-life when administered vaginally than orally. 8 However the short half-life of oral misoprostol may be an advantage in induction of labour, because of the less risk for hyperstimulation of uterus and less tachysystole.

The advantage of misoprostol orally with particular reference to prelabour rupture of membranes, is avoidance of repeated vaginal examinations resulting in less risk of sepsis for the mother and baby. 10

Dose for oral misoprostol for induction labour varies from 50mgm-100mgm, every four hours. In one study, oral Misoprostol 50ugm four hourly resulted in a longer induction to vaginal delivery interval. 10 A meta analysis of the Cochrane library suggested that oral misoprostol for labour induction in a dose of 100mgm or more, although effective, may prove to be too high, particularly in parous women with ruptured membranes or a favourable cervix. 11

The objective of this study was to assess the effectiveness, safety and maternal satisfaction of an oral dose of 50mgm misoprostol every four hours in women with PROM at term. The outcome measures studied included induction to delivery interval, operative delivery rates, and the neonatal and maternal outcomes.

Subjects and Methods

The study was carried out in the department of Obstetrics and Gynecology, Civil Hospital, Karachi between January 2001- December 2003. The inclusion criteria were a gestation period of >37 weeks, singleton pregnancy, rupture of membranes detected by seeing a pool of amniotic fluid in speculum examination and a reactive caridotocographics trace. The exclusion criteria were active labour, signs and symptoms suggestive of chorioamnionitis, signs of fetal distress including meconium or/and a non-reassuring caridotocographics trace and presence of other maternal and fetal factors contraindicating induction of labour. Eligible women were counselled regarding the study.

Patients were initially seen in the labour ward when presenting with a history of leaking amniotic fluid. After obtaining the history which included age, parity, gestational age, duration of leakage of amniotic fluid, presence of other associated maternal diseases, examination was performed A fixed presenting part was confirmed by abdominal examination. A cardiotocographic trace confirmed fetal well being and a high vaginal swab was taken for direct microscopy, gram staining and culture.

Once all the inclusion criteria for the study were fulfilled, vaginal examination was performed under sterile conditions to assess the Bishop score.

Patients were then give 50mgm of oral misoprostol, which was prepared by dividing a 200ugm tablet into four quarters. The dose of 50ugm was repeated after four hours if there was no uterine activity or if the uterine contractions were mild (less than two contractions in 10 minutes). A maximum of three doses were given. Once uterine contractions were established, patients were shifted to labour room where augmentation with oxytocin infusion was started according to cervical dilatation. If at the end of three doses of misoprostol labour had not set in, oxytocin was given for induction. Non-responders were subjected to caesarean section as patients with failed induction.

The variables studied included age, parity, induction to delivery interval, mode of delivery and maternal side effects including uterine hyperstimulation, tachysytole six or more contractions in 10 min or sustained contractions over two minutes, nausea, vomiting, pyrexia, maternal temperature of 380C. Fetal outcomes in terms of apgar score at 5 minutes and NICU admissions were noted.

Results

During the study period, 104 patients were eligible for inclusion, of whom 86 (82.7%) were between 20-30 years of age. Only 2 (1.9%) were less than 20 years. Thirteen (12.5%) were between 30-35 years and 3 (2.9%) were more than 35 years of age. There were 28 (26.9%) primigravida, 60 (57.7%) had given birth to one to three babies, 14 (13.5%) were para 4-5 and only 2 (1.9%) were grand multipara.

Table 1 shows the induction delivery interval in hours with relationship to parity. The induction delivery interval was longer in primigravida with only 4 (14.3%) patients delivering within 12 hours, as compared to multigravida with 55 (72.4%) achieving a vaginal delivery within 12 hours of induction. There were more failed inductions in primigravida 4 (14.3%) patients, as compared to multigravida 2 (2.6%) patients.

Regarding the Bishop's score at admission (Table 1), the induction delivery interval was shorter when Bishop score was more than 5 and longer when Bishop score was less than 5.

Table 2 shows the maternal side effects associated with oral misoprostol. Ten (9.6%) patients had tachysystole, 2 had uterine hyper stimulation (1.9%), 68 (65.3%) nausea and vomiting and 9.6% (10 patients) had pyrexia with temperature of >38°C. Fifteen (14.4%)

Table 1. Induction delivery interval (n = 104).
Hours Parity Bishop's score
Primigravide > 1 <5 >5 Total
(n=28) (n=76) (n=104)
No. % No. % No. % No. % No. %
Vaginal delivery within 12 hours 4 14.3 55 72.4 10 9.6 49 47.1 59 56.7
Vaginal Delivery within 24 hours 20 71.4 19 25 12 11.5 27 26 39 37.5
Failed inductions 4 14.3 2 2.6 6 5.8 0 - 6 5.8

 
Table 2. Maternal side effect (n=104)
No. %
Tachysystole 10 9.6
Uterine Hyperstimulation 2 1.9
Nausea And Vomiting 68 65.3
Pyexia > 38 o C 10 9.6
Postpartum Hemorrhage 15 14.4
Uterine Rupture 1 0.96

 
Table 3. Neonatal outcome (n=104).
No. %
Apgar score at 5 minutes
< 5 30 24.9
> 5 74 71.1
NICU Admission 10 9.6
Still Births - -
Neonatal Deaths 2 1.9

Discussion

The study provides the effects of oral misoprostol in patients with prelabour rupture of membranes at term. The trial includes active management of labour in PROM using misoprostol as a drug for inducing labour. Induction has advantages over expectant management as it decreases the risk of maternal and neonatal infections and increases maternal satisfaction 12,13 as is also evident from our study.

Using oral misoprostol for labour induction reduces the frequency of vaginal examinations and use of intravenous line only later in labour and therefore the patients may not have felt as restricted in early stage of labour. This may partly explain the increased satisfaction in this group.

The large randomized controlled trail by Hannah et al. 14 on the management of prelabour rupture of membranes at term showed that although active induction of labour with oxytocin or PGE2 vaginal gel resulting in shorter prelabour rupture of membranes to delivery interval, it does not result in the decrease in the rate of neonatal infections or operative delivery rates as compared with expectant management (upto four days). However, tials do show that infection rates in active induction of labour with oxytocin infusion are lower than both the vaginal prostaglandin and the expectant management group and this was mainly due to more vaginal examinations in these groups. Using oral misoprostol for labour induction thus reduces vaginal examinations during labour and repeating the dose of oral misoprostol on uterine contraction assessment will be appropriate.

Regarding the induction delivery interval, both Bishop score and parity appears to be important predicators 15 as is also evident in our study. A favourable Bishop score is associated with the shorter induction to delivery interval as compared to multigravidae.

The most significant side effects recorded with the oral misoprostol were nausea and vomiting followed by pyrexia and uterine hyper stimulation. Post partum hemorrhage mainly occurred in multigravidae and in those primigravida who had longer induction to delivery intervals. Only one multigravida had uterine hyperstimulation with incomplete uterine rupture necessitating an immediate caesarean section. Caesarean section were mainly performed because of fetal distress, and failed inductions.

Monitoring during labour is important when using misoprostol for labour induction, to detect uterine hyperstimulation and fetal distress and early intervention if any such condition arise in order to achieve a good maternal and fetal outcome.

Our study suggests that women with PROM at term were satisfied with active induction of labour and delivery with oral misoprostol resulting in shorter induction to delivery intervals and good fetal outcome. Oral misoprostol can be used safely as an alternative to oxytocin infusion or prostaglandin vaginal pessaries/gel for labour induction in women with PROM at term.

Reference

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15. Wing DA, Trans S, Paul RH. Factors affecting the likelihood of successful induction after intravaginal misoprostol applications for cervical ripening and labour induction. Am J Obstet Gynecol 2002;186:1337-43.

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