398 The impact of BMI on management of labour: A retrospective matched cohort analysis

Abstract

Maternal obesity is a major challenge to safe obstetric practice with higher rates of intrapartum complications, failed induction of labour (IOL) and emergency caesarean delivery (CD). We investigated the impact of obesity on labour outcomes and interventions. Class III obese (BMI >40 Kg/m2) and normal BMI (<25 Kg/m2) patients who delivered from 2015-2018 were matched (1:1) based on age, gestational age, parity, onset of labour, and birth weight. Patients with previous CD, IOL < 37 weeks, maternal age <18 years or stillbirth were excluded. The primary outcome was CD. Secondary outcomes were instrumental delivery, cervical dilation at decision for CD, dilation rate prior to decision for CD for labour progress, oxytocin augmentation, and intrapartum interventions (epidural analgesia, fetal scalp electrode (FSE), intrauterine pressure catheter (IUPC), fetal scalp lactate, terbutaline use). Of 600 matched patients, 50% were primigravidae (PG). Half of both PG and multigravidae groups underwent IOL. CD rate was higher for obese (oBMI) patients (19.3%) than the normal BMI (nBMI) cohort (13.3%, RR 1.45, CI 1.00-2.09, p = 0.049). Instrumental deliveries occurred less in oBMI (16.7%) than with nBMI (24.0%, RR 0.89, CI 0.50-0.96, p = 0.027). Median cervical dilation at CD was lower for oBMI (4 cm) than nBMI (6 cm), even when comparing only CD for poor progress (5 cm vs 7 cm). Rate of dilation prior to CD for poor progress was lower in oBMI (0.04cm/hr) than nBMI (0.16cm/hr). In CD patients, oxytocin was used less often for oBMI (75.8% vs 85.0%, RR 0.89, CI 0.73-1.08, p = 0.253) but with a higher mean total dose (12.3 IU vs 11.9 IU). Rates of intrapartum intervention were higher for oBMI, particularly FSE (72.7% vs 22.7%, RR 3.21, CI 2.52-3.99, p < 0.001) and IUPC (55% vs 0%, p < 0.001). Obesity increased the risk of CD, and CD for poor progress occurred at a lower cervical dilation in the obese cohort, with a slower rate of dilation prior to CD. Intrapartum interventions occurred more in the obese cohort.