Association Between body Mass Index in Early Pregnancy and the Outcomes of Induction of Labour at Kenyatta National Hospital

Abstract

Introduction: Body mass index (BMI) has many medical implications. High BMI has been shown to increase the risk of certain obstetric complications. Induction of labour (IOL) is a common obstetric intervention and the various outcomes of IOL have been well documented. Failed induction is a possible outcome of IOL and various physiologic and anatomic factors including BMI have been cited as possible risks. Local studies are lacking on how BMI may affect the process of IOL and that was the purpose of this study. Objective: To determine the association between body mass index in early pregnancy and the outcomes of induction of labour at Kenyatta National Hospital. Study setting: The study was conducted in the Kenyatta National Hospital labour ward. Study design: A comparative cross sectional study. Study population: The study included pregnant women planned for induction of labour with misoprostol. A total of 204 women were included with 103 women having normal BMIand 101 women with BMI of 25or above. Study methodology: Between the months of June and October 2018, eligible women were recruited consecutively into the study once a decision to induce labour was made. Baseline data was obtained and they were then allowed to continue with IOL as per the Kenyatta National Hospital protocol until delivery of the baby. Outcomes of interest were recorded after the mother had delivered. These outcomes included failed induction of labour, the mode of delivery, the neonatal APGAR score at five minutes, the need for augmentation of labour and any fatal maternal or neonatal outcomes. Results: Most of the women in the study were in their second decade of life, married, self employed or unemployed. The women with high BMI were more likely to have had a prior delivery and they gave birth to heavier babies. The indications for IOL included postdatism, reduced foetal movements at term, rhesus negative blood type and elective induction at term. The overall rate of failed IOL was 11.8%, Caesarean section rate was 28.4% and 60.2% of all the women who achieved labour required augmentation with oxytocin. The most common indication for Caesarean section was failed induction in the high BMI group and prolonged labour in the normal BMI group. The Caesarean section rate did not significantly differ between the two groups. The rate of failed IOL was higher in the high BMI group (OR 3.5; CI 1.3, 9.2; p 0.008) as compared to the normal weight women. A high BMI change during pregnancy was however not associated with higher odds of the outcomes.

Conclusion: High early pregnancy maternal BMI is associated with a higher likelihood of failed IOL. After induction of labour at term with misoprostol, women with above normal BMI are more likely to go for Caesarean section due to failed IOL as compared to normal BMI women. Recommendations: Women should be counselled about achieving appropriate weight preconceptionally. Those with high BMI and undergoing IOL should also be informed about possible outcomes of induction of labour, including a higher risk of induction failure. Further to this, various ways of achieving labour in overweight and obese women should be explored.