The impact of body mass index on labour management and mode of delivery: A retrospective matched cohort study

Aim: This study aims to examine the association between body mass index (BMI) and mode of delivery, progression of labour, and intrapartum interventions. Methods: This was a retrospective matched cohort study including Class III obese (BMI ≥40 kg/m2) and normal BMI (BMI <25 kg/m2) women planning a vaginal birth who had a live, singleton delivery from January 2015 to December 2018. Patients were matched (1:1) based on age, gestational age, parity, onset of labour and birth weight. The primary outcome was caesarean delivery (CD). Secondary outcomes were delivery outcomes, intrapartum management and interventions. Rates of each outcome were compared with matched analysis, and duration of labour with time-to-event analysis. Results: We studied two groups of 300 pregnant women. The CD rate was significantly higher for obese women than the normal BMI cohort (19.3% vs 13.3%; risk ratio (RR) 1.43, 95% CI 1.02–1.98, P = 0.035). Cervical dilation prior to CD for failure to progress was slower in obese than normal BMI (0.04 vs 0.16 cm/h). The obese cohort had a longer duration of labour in those who underwent induction (13.70 vs 11.48 h, P = 0.024). Intrapartum intervention rates were higher for obese women, with significant differences in rates of fetal scalp electrodes (72.7% vs 22.7%, RR 3.20, 95% CI 2.58–3.99, P < 0.001), intrauterine pressure catheters (18.3% vs 0%, P < 0.001), epidural analgesia (44.0% vs 37.0%, RR 1.20, 95% CI 1.01–1.44, P = 0.040) and fetal scalp lactate sampling (8.0% vs 3.0%, RR = 2.67, 95% CI 1.33–5.33, P = 0.004). Conclusion: Class III obesity is associated with an increased risk of CD and intrapartum interventions.