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Maternal Obesity Increases Risk for Birth Defects
Maternal obesity and overweight increased risk for many birth defects, but obesity decreased risk for gastroschisis.
Prepregnancy obesity has been associated with birth defects, particularly spina bifida, but data are limited. To further examine this association, researchers analyzed data from the National Birth Defects Prevention Study, an ongoing multisite case-control study. Sixteen categories of birth defects were analyzed, and self-reported height and prepregnancy weight were used to calculate body-mass index.
In analysis adjusted for potential confounders including maternal age, parity, smoking, and folic acid supplement intake, maternal obesity (BMI 
30 kg/m2) was associated with significantly increased risks among infants for spina bifida, heart defects, anorectal atresia, hypospadias, limb reduction defects, diaphragmatic hernia, and omphalocele (adjusted odds ratios ranging from 1.33 to 2.10). Excluding mothers with gestational diabetes decreased the associations slightly between each of the seven birth defects and maternal obesity. Maternal obesity was associated with significantly decreased risk for gastroschisis (AOR, 0.19). Maternal overweight (BMI 25 and <30) posed a similarly increased risk for heart defects, hypospadias, and omphalocele.
Comment: Maternal obesity is a significant risk factor for many types of birth defects. In this study, the positive associations were not strong, unlike the protective effect of maternal obesity on gastroschisis. Although the reasons for the associations have not been determined, the authors believe that undiagnosed gestational diabetes or insulin resistance may be involved.
— Robert A. Dershewitz, MD, MSc
Published in Journal Watch General Medicine August 28, 2007
Citation(s):
Waller DK et al. Prepregnancy obesity as a risk factor for structural birth defects. Arch Pediatr Adolesc Med 2007 Aug; 161:745-50.
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