Maternal Obesity and Nonstress Testing

We evaluated the impact of maternal obesity on the characteristics and results of nonstress tests (NST). This prospective 1-year cohort study included 2026 NSTs performed on 575 consecutively chosen women with singleton gestations >= 32 weeks and no known fetal anomalies. Body mass index (BMI) class was determined at the first prenatal visit. The primary outcome was the duration of fetal heart rate monitoring before a reactive result. Obese women were not more likely to have nonreactive NST results. The mean duration before obtaining a reactive result was unaffected by obesity after controlling for diabetes and gestational age. The overall number of NSTs per patient was higher in obese than in nonobese women (3.9 versus 3.1, p < 0.01). More tests per patient are performed among obese subjects, yet the ability to perform an NST and the duration before obtaining a final result were unaffected by obesity.