Obesity and extreme obesity: New insights into the black-white disparity in neonatal mortality

OBJECTIVE: To estimate whether the preponderance of obesity among black women could explain the black-white disparity in neonatal mortality. METHODS: This is a population-based study using longitudinally collected data among pregnant women from the state of Missouri spanning almost two decades (19781997). Obesity is defined in this study as body mass index (BMI) of at least 30 and further categorized into the typically reported three subclasses: class I (BMI 30.0-34.9), class 11 (BMI 35.0-39.9), and extreme/morbid obesity (BMI at least 40). The main outcome measures were neonatal mortality, early neonatal mortality, and late neonatal mortality. RESULTS: Overall, neonatal mortality and early neonatal mortality but not late neonatal mortality increased with higher obesity subclass, with the greatest risk registered among morbidly obese mothers (hazards ratio for neonatal mortality 1.3; 95% confidence interval [CI] 1.1-1.5; hazards ratio for early neonatal mortality 1.3; 95% CI 1.1-1.5). Among blacks, the risk for neonatal, early, and late neonatal mortality increased significantly with rising BMI (50-100% increments). However, offspring of obese white mothers had no elevated risks for any of the three indices of mortality regardless of maternal obesity subclass. CONCLUSION: Neonates of obese black mothers have an elevated risk of mortality throughout the neonatal period, whereas those of obese white mothers do not. Obesity among black mothers may contribute to the persistent black-white disparity in infant survival in the United States and could provide an avenue for narrowing the black-white gap in infant mortality.