Predictors Of Successful Induction Of Labour In Post-term Pregnancies At Kenyatta National Hospital

Abstract

Background: A post-term or prolonged pregnancy according to World Health Organization (WHO) is one that has exceeded 294 days from the last normal menstrual period. A prolonged pregnancy can lead to post-maturity of the fetus posing a great threat to its further survival in-utero and multiple complications including neonatal mortality post delivery. World-wide 5-10% of all pregnancies are prolonged with 20% of post-term fetuses having dysmaturity syndrome. The incidence of induction is on the rise, half of which are due to post-dates. At Kenyatta National Hospital the rate of induction of labour due to prolonged pregnancies stands at 50 % of all inductions. The failure of induction world-wide has been increasing and it is therefore important to determine some of the predictors of successful induction. Several studies have been done world-wide to predict factors influencing failed induction but there has been none specifically for predictors of successful induction in post-dates. Objectives: To determine the predictors of successful induction of labour in post-term pregnancies at Kenyatta National Hospital. Study design: Descriptive cross-sectional study among post-term pregnant women delivering at Kenyatta National Hospital (KNH). Study setting: The labour ward and post-natal wards at Kenyatta National Hospital Study participants: 188 post-term pregnant women, with a live fetus undergoing induction of labour with no alternate indication for induction. Methodology: This was a descriptive cross-sectional study on post-term pregnant women admitted for labour induction at Kenyatta National Hospital between January and April 2013. 188 patients with gestational age of ≥ 41 weeks undergoing induction of labour during the study xii period were consecutively recruited into the study until the sample size was reached. A questionnaire was used to obtain data about the socio-demographics, gestational age and parity. The pre-induction Bishop Score, the birth weight of the infant, methods of induction and the outcome of the induction process was availed from the patients file. Results: A total of 188 women were induced due to post-term pregnancies. Most of the participants (76%) were aged between 20 and 29 years. Majority of the women were primi-gravidae (58%), and the mean gestational age was 41.14 weeks (range 41-42 weeks). The success rate of induction among study participants was 68 %. Prostaglandins in combination with artificial rupture of membranes and Oxytocin infusion was the most common method used for inducing labour. Multiparity and a favourable Bishop score were significant predictors of successful induction in post-term pregnancies. Bishop scores ≥6 were associated with higher success rates for labour induction (85.2%) versus 60.4% in those with lower Bishop scores. Infants less than 4000grams had higher rates of vaginal deliveries (72.8%) compared to those with more than 4kgs (6.7%). Age of the patient and the modality of induction were not determining factors in induction of post-term pregnant women in this study. Conclusions and recommendations: In conclusion Bishop score of ≥ 6, multi-parous patients and mothers with infants having a birth weight of < 4000grams had a higher rate of successful induction. A pre-induction estimated fetal weight should be a routine practice to select the right patients for the induction process. Mothers with estimated fetuses over 4000grams should be offered an elective caesarean as an option.