Maternal obesity is associated with a significantly increased risk of fetal structural anomalies, including neural tube defects and cardiac malformations, according to a meta-analysis.
The risk for some of these anomalies also was elevated among women who were overweight but not obese. Future studies should investigate whether there is a dose-response relationship between maternal weight and risk of structural abnormalities, said Katherine J. Stothard, Ph.D., and her associates at Newcastle University, Newcastle upon Tyne, England (JAMA 2009;301:636–50).
The researchers reviewed 39 relevant articles in the English literature and performed a meta-analysis of 18 that were the most scientifically sound, excluding studies with fewer than 150 cases of a particular congenital anomaly and studies of abnormalities that were chromosomal or syndromic in origin. They included cases in which pregnancies were terminated when congenital anomalies were discovered.
Compared with mothers at recommended body weights, obese mothers were nearly twice as likely to have a pregnancy affected by neural tube defects, including spina bifida and anencephaly. Their risk ranged from 1.2 to 1.7 times to have a fetus with a heart anomaly, a facial anomaly such as cleft palate or cleft lip, or other anomalies including anorectal atresia, hydrocephaly, and limb reduction.
Some anomalies could not be examined in this meta-analysis because studies of those defects were not sufficiently powered to detect significant effects. However, the review showed that the association with maternal obesity approached significance for omphalocele, craniosynostosis, and simultaneous multiple anomalies.
Both neural tube defects and cardiac anomalies also were more likely to occur in mothers who were overweight but not frankly obese. Future studies should assess structural congenital anomalies across “the complete range of [body mass index],” Dr. Stothard and her associates said.
“Many of the congenital anomalies implicated in this review have similar developmental timing and responsiveness to folic acid, suggesting a common underlying etiology,” they added.
Dr. Stothard received funding from BDF Newlife.