Objective: To evaluate whether adverse neonatal outcome, defined as birth injuries or severe illnesses in the newborn, was associated with maternal body mass index (BMI) in singleton pregnancies overall and depending on mode of delivery.
Methods: This was a cohort study including 1,024,471 women. Data were collected from the Swedish Medical Birth Registry. Women were categorized into six classes of BMI. Obese women were compared with normal weight women regarding adverse neonatal outcome after suitable adjustments. Four modes of delivery were evaluated: vaginal delivery; instrumental vaginal delivery; elective cesarean delivery; and emergency cesarean delivery.
Results: Compared with neonates born to women of normal weight, neonates born to women with BMIs of 40 or more (morbidly obese) were at increased risk of birth injury to the peripheral nervous system (odds ratio [OR] 3.80, 95% confidence interval [CI] 2.83-5.12; 0.2% compared with 0.6%), birth injury to the skeleton (OR 2.59, 95% CI 2.10-3.21; 0.5% compared with 1.1%), respiratory distress syndrome (OR 2.08, 95% CI 1.88-2.30; 2.9 compared with 5.8%), bacterial sepsis (OR 2.90, 95% CI 2.43-3.46; 0.6% compared with 1.7%), convulsions (OR 3.43, 95% CI 2.63-4.47; 0.2% compared with 0.8%), and hypoglycemia (OR 3.48, 95% CI 3.20-3.78; 2.4% compared with 7.9%). For morbidly obese women, elective cesarean delivery and vaginal delivery were associated with twice the increased risk of adverse neonatal outcomes when compared with women of normal weight.
Conclusion: Neonates born to morbidly obese women are at markedly increased risk of adverse neonatal outcome regardless of mode of delivery. Obstetricians should not disregard the neonatal problems associated with elective cesarean delivery for morbidly obese women.
Level of evidence: II.