Influence of maternal obesity on Bishop Score and failed induction of labour: A retrospective cohort study in a regional tertiary centre

Abstract

Maternal obesity is a growing health concern that has previously been associated with increased need for induction of labour (IOL) and caesarean section (CS) rates. Currently, limited evidence explores the influence of maternal body mass index (BMI) on Bishop Score (BS) and outcome of IOL. This study hypothesises that maternal obesity will lead to a lower BS at presentation, higher rates of failed IOL, and increased CS rates. To explore the influence of maternal obesity on BS and likelihood of failed IOL. A retrospective cohort analysis was conducted of all live, term, singleton, cephalic deliveries initiated with IOL across normal BMI (18.00-24.99), overweight BMI (25.00-29.99), and obese BMI (>30.00) at the Townsville Hospital and Health Service (THHS) between July 2011 to June 2016. Student's t-test, χ2 test, and binary logistic regression were used for statistical analysis. BS and failed IOL, defined as CS with cervical dilatation <3 cm, were the primary outcome measures. Delivery mode was the secondary outcome measure. A total of 1543 women were included, 678 with normal BMI, 370 with overweight BMI, and 495 with obese BMI. Obese women are more likely to have a low BS (<5) at presentation (unadjusted odds ratio (OR) 1.5 (1.1-2.0), P < 0.05), an increased rate of failed IOL (adjusted OR (aOR) 1.6 (1.0-2.5), P < 0.05) and increased CS rate (aOR 1.1 (1.0-1.9), P < 0.05), compared to normal weight women. Maternal obesity is associated with a lower BS, more difficult IOL process, and increased risk of failed IOL and CS.