Maternal body mass index as a predictor for delivery method

High maternal body mass index (BMI) is associated with complications during pregnancy and delivery such as gestational diabetes, hypertensive disorders, perineal injuries and macrosomia. The aim of this study was to assess the association between maternal BMI and delivery method in non-breech, singleton deliveries, after 36 weeks of gestation, in women with no more than one previous cesarean section, in Oslo University Hospital, Ullevål.

This retrospective register study used data from the hospital obstetrical database in 2011-2012, forming a cohort of 8821 women. Women were categorized into five different BMI classes and stratified into subgroups according to parity and previous cesarean delivery. Mode of delivery was categorized to spontaneous delivery, instrumental vaginal delivery, planned cesarean section and emergency cesarean section.

Incidence of emergency cesarean delivery increased with increasing maternal BMI. Among primiparous women with overweight or obesity, the caesarean delivery rate was doubled (23.2 and 29.1%, respectively), compared with women with underweight or normal weight (12.5 and 13.7%). Also among parous women, maternal BMI ≥30 doubled the risk for cesarean delivery. The strongest risk factor for planned or emergency cesarean delivery was previous cesarean section [adjusted odds ratio 16.41 (confidence interval 12.19-22.08) and 8.72 (6.33-12.02), respectively]. Maternal BMI ≥30 increased the risk of planned cesarean delivery by 77%, and doubled the risk of emergency cesarean delivery.

Prepregnancy BMI ≥30 was an independent risk factor for delivery by emergency cesarean section for both primiparous and parous women.