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

Background 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. Aims To explore the influence of maternal obesity on BS and likelihood of failed IOL . Methods 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, χ 2 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. Results 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. Conclusions Maternal obesity is associated with a lower BS , more difficult IOL process, and increased risk of failed IOL and CS.