BACKGROUND

Maternal obesity is associated with increased systemic inflammation and an increased risk of preterm premature rupture of membranes. There is an established association between an inflammatory intrauterine environment and adverse neonatal outcomes that is independent of gestational age and mediated by the fetal inflammatory response. It is unknown whether the maternal systemic inflammation that is present in obese women influences the intrauterine environment and predisposes the fetus to adverse neonatal outcomes after preterm premature rupture of membranes.

OBJECTIVE

The purpose of this study was to determine whether maternal obesity is associated with adverse neonatal outcomes in pregnancies that are complicated by preterm premature rupture of membranes.

STUDY DESIGN

This was a secondary analysis of the Maternal-Fetal Medicine Units Network Randomized Clinical Trial on the Beneficial Effects of Antenatal Magnesium Sulfate. Women with singleton pregnancies that were affected by preterm premature rupture of membranes who delivered live-born infants between 24 + 0 and 33 + 6 weeks of gestation were included. An adverse neonatal outcome was defined as a composite outcome of neonatal death, severe necrotizing enterocolitis, respiratory distress syndrome, sepsis, or severe intraventricular hemorrhage. The rates of the composite outcome were compared between obese (body mass index, ≥30 kg/m(2)) and nonobese women. Multivariable logistic regression was used to evaluate the independent effect of obesity on neonatal outcomes. Magnesium sulfate administration, steroid administration, maternal diabetes mellitus, gestational age at delivery, indomethacin exposure, birthweight, and chorioamnionitis were all considered as possible covariates in the multivariable regression models.

RESULTS

Three hundred twenty-five of the 1288 women (25.2%) who were included were obese, and 202 of these women (62.2%) had neonates with adverse outcomes. In univariable analysis, maternal prepregnancy obesity was associated with increased odds of an adverse neonatal outcome (odds ratio, 0.30, 95% confidence interval, 1.00-1.68). However, in our multivariable logistic regression model, gestational age at delivery (odds ratio, 0.93, 95% confidence interval, 0.92-0.94 per day), but not maternal obesity (odds ratio, 1.02, 95% confidence interval, 0.75-1.38), was associated with adverse neonatal outcomes. Obese African American women experienced preterm premature rupture of membranes (189 vs 196 days; p < .001) and delivery (199 vs 205 days; p < .001) earlier than nonobese African American women. This difference was not seen in non-African American women.

CONCLUSIONS

Maternal obesity was not associated independently with adverse neonatal outcomes in pregnancies that were affected by preterm premature rupture of membranes after adjustment for gestational age at birth. However, obese African American women rupture and deliver earlier than other women, which causes increased neonatal morbidity.