Labour Progression in Obese Women: Are Women With Increased Body Mass Index Having Unnecessary Cesarean Sections?

Objective: This study sought to determine whether obese pregnant women undergo cesarean sections without an adequate trial of labour. This may affect future birth and pregnancy outcomes. Methods: A retrospective analysis was done on 526 parturients at Victoria Hospital in London, Ontario. Women were categorized according to parity and pre-pregnancy body mass index (BMI; normal weight, BMI 18.5-24.9 kg/m(2); obese class II, BMI 35.0-39.9 kg/m(2); obese class III, BMI >= 40 kg/m(2)). Patient charts and partograms were reviewed for labour progression (time at cervical dilation), demographics, and infant outcomes (Canadian Task Force Classification II-2). Results: Obese class II and III primiparous women required an additional 1.62 and 2.67 hours (P = 0.012), respectively, to reach a dilation of 10 cm compared with their normal weight counterparts; obese class II and III multiparous women required an additional 1.25 and 2.05 hours (P = 0.003), respectively. A higher BMI was associated with increased oxytocin use and infant birth weight in primiparous women. Obese women had less gestational weight gain and required more cervical examinations. Cesarean section rates were low for obese parturients (primiparous, 19%; multiparous, 0.8%) and not significantly different among BMI categories. Conclusion: This study confirmed published results that labour progresses more slowly as maternal BMI increases. The study was performed in a centre with a specialized BMI pregnancy clinic; thus weight gain adherence, awareness of labour differences, and patient counselling may have contributed to low cesarean section rates. Obstetric care providers should consider differences in maternal BMI in labour progression before undertaking a potentially premature cesarean birth, especially in primiparous women.