Maternal obesity and neuroprotective magnesium sulfate.

OBJECTIVE: Given the association between risk of cerebral palsy and children born to obese women, the study aim was to estimate whether maternal obesity is associated with reduced effectiveness of conventional antenatal magnesium sulfate dosing for the prevention of cerebral palsy and death.

STUDY DESIGN: This is a secondary cohort analysis of a multicenter randomized clinical trial completed by the Maternal-Fetal Medicine Units Network. Women were included in the original trial if deemed high risk for preterm delivery in the subsequent 24 hours. The present study included singleton, nonanomalous fetuses that were randomized to and received magnesium sulfate with complete data available. Outcomes between obese (body mass index ≥30 kg/m(2)) and nonobese women were compared. A secondary analysis of outcomes between morbidly obese (body mass index ≥40 kg/m(2)) and nonmorbidly obese women was performed. The primary outcome was a composite of cerebral palsy or perinatal death before 15 months corrected age. Secondary outcomes included moderate to severe cerebral palsy or death, any cerebral palsy, moderate to severe cerebral palsy, and death. A logistic regression analysis was used to estimate the odds ratio of each outcome. Based on sample size, exposure rate (obesity) and an outcome rate of 10%, assuming an 80% power and a 0.05 alpha error, this study had sufficient power to detect a 2-fold increase in the primary outcome.

RESULTS: Of 1188 women randomized to receive magnesium sulfate, 806 were included in this analysis. After adjusting for gestational age at delivery, maternal obesity was not associated with an increased risk of cerebral palsy or death in children born to women who received magnesium sulfate. Women with morbid obesity had higher rates of the primary outcome and cerebral palsy in an unadjusted analysis but did not have increased risks after adjusting for gestational age at delivery. In analyses stratified on gestational age, morbidly obese women who delivered after 28 weeks had increased risks of children with cerebral palsy or death and cerebral palsy, although case numbers were small.

CONCLUSION: Among women receiving antenatal neuroprotective magnesium sulfate, maternal obesity is not associated with an increased risk of having a child with cerebral palsy or death.