Influence of class III obesity on mode of delivery and perinatal complications in nulliparous women: A matched case-control study

Objective: Obesity class III, defined as a body mass index (BMI, calculated as weight in kilograms divided by the square of height in meters) exceeding 40, is associated with significant maternal and perinatal morbidity. The primary objective of this study was to evaluate the independent effect of class III obesity on mode of delivery and perinatal outcome. Methods: A matched case-control study was conducted, involving pairing a cohort of 69 nulliparous patients with a BMI ≥ 40 to two control groups of pregnancies (70 with maternal BMI 30-39 and 70 with BMI < 30). Subjects were matched for gestational diabetes mellitus (GDM) status and maternal age. Exclusion criteria were multiparity, multiple gestation, pregnancy loss < 24 weeks' gestation and pre-pregnancy diabetes. Patterns across the BMI groups were tested using the Cochrane-Armitage trend test and the Mann-Kendall trend test. A P value less than 0.05 was considered statistically significant. Results: While the planned cesarean delivery (CD) rate was similar across BMI categories, class III obesity was independently associated with a statistically significant increase in the requirement for intrapartum CD (n = 32/60 [53%, excluding elective prelabor CD]) compared with BMI 30-39 (n = 24/61 [39%, excluding elective prelabor CD]) and BMI < 30 (n = 16/62 [26%]) (P = 0.006). This increase was observed both in spontaneous and induced labor. The decision to induce labor was significantly higher in the class III obesity group (n = 49/69 [82%]) compared with BMI 30-39 (n = 44/70 [79%]) and BMI < 30 (n = 30/70 [49%]) (P < 0.001). The most prevalent complication was cesarean wound infection requiring re-hospitalization, occurring in 20% of the class III group. Conclusion: Almost 60% of nulliparous pregnancies complicated by class III obesity require CD, the majority being intrapartum. Adjusting for the potential influence of maternal age and GDM status on perinatal decision making provides valuable insight into the independent effect of class III obesity on delivery outcome. When safely feasible, efforts should be directed toward awaiting spontaneous labor to optimize the prospect of achieving vaginal birth