Maternal Obesity and the Risk of Infant Death in the United States

Background: Maternal obesity (defined as prepregnancy body mass index [BMI] >= 30 kg/m(2)) is associated with increased risk of neonatal death. Its association with infant death, postneonatal death, and cause-specific infant death is less well-characterized. Methods: We studied the association between maternal obesity and the risk of infant death by using 1988 US National Maternal and Infant Health Survey data. A case-control analysis of 4265 infant deaths and 7293 controls was conducted using SUDAAN software. Self-reported prepregnancy BMI and weight gain were used in the primary analysis, whereas weight variables in medical records were used in a subset of 4308 women. Results: Compared with normal weight women (prepregnancy BMI 18.5-24.9 kg/m(2)) who gained 0.30 to 0.44 kg/wk during pregnancy, obese women had increased risk of neonatal death and overall infant death. For obese women who had weight gain during pregnancy of <0.15, 0.15 to 0.29, 0.30 to 0.44, and >= 0.45 kg/wk, the adjusted odds ratios of infant death were 1.75 (95% confidence interval = 1.28-2.39), 1.42 (1.07-1.89), 1.59 (1.00-2.51), and 2.87 (1.98-4.16), respectively. Nonobese women with very low weight gain during pregnancy also had a higher risk of infant death. The subset with weight information from medical records had similar results for recorded prepregnancy BMI and weight gain. Maternal obesity was associated with neonatal death from pregnancy complications or disorders relating to short gestation and unspecified low birth weight. Conclusions: Maternal obesity is associated with increased overall risk of infant death, mainly neonatal death.