Adverse maternal and neonatal outcomes among low-risk women with obesity at 37-41 weeks gestation

Objective: To evaluate adverse neonatal and maternal outcomes among women with obesity and no additional comorbidities at 37-41 weeks.

Methods: This was a population based retrospective cohort study performed using US vital statistics data from 2014-2017. We included women with body mass index ≥ 30.0 kg/m² and a singleton, cephalic, non-anomalous pregnancy who attempted labor and delivered between 37 0/7-41 6/7 weeks. Women with chronic hypertension, gestational diabetes, or pregestational diabetes were excluded. The co-primary outcomes were composite neonatal morbidity (Apgar score < 5 at 5 min, assisted ventilation > 6 h, neonatal seizures, or neonatal death within 27 days) and composite maternal morbidity (admission to the intensive care unit, blood transfusion, uterine rupture, or unplanned hysterectomy) with completed weeks of gestation as the primary exposure variable. All outcomes were examined using multivariate Poisson regression and were reported as adjusted risk ratios (aRR) with 95 % confidence intervals (95 % CI).

Results: There were 15.8 million live births between 2014-2017, of whom 5.1 million (32.1 %) met the inclusion criteria. Composite neonatal morbidity was significantly increased in women delivering at 37 weeks (aRR 1.84; 95 % CI 1.78-1.90), 38 weeks (aRR 1.14; 95 % CI 1.10-1.17), 40 weeks (aRR 1.19; 95 % CI 1.16-1.22), and 41 weeks (aRR 1.49; 95 % CI 1.44-1.53) compared to 39 weeks. Composite maternal morbidity was similarly increased at 37 weeks (aRR 1.26; 95 % CI 1.19-1.34), 38 weeks (aRR 1.07; 95 % CI 1.02-1.13), 40 weeks (aRR 1.16; 95 % CI 1.11-1.20), and 41 weeks (aRR 1.42; 95 % CI 1.34-1.49).

Conclusion: Composite neonatal and maternal morbidity among women with obesity and no additional comorbidities is increased with delivery at 37, 38, 40, or 41 weeks compared with 39 weeks.