Obesity and the risk and detection of fetal malformations

The incidence of obesity in pregnancy has increased over the past 2 decades, with nearly 50% of U.S. women aged 15-49 years classified as overweight or obese. Obesity (independent of diabetes) among gravidae poses unique risks that extend toward the fetus, with several large population-based analyses demonstrating independent increased risks for fetal malformations including neural tube defects, cardiac anomalies, and orofacial clefts, as well as stillbirth and macrosomia. Unfortunately, several lines of evidence also suggest that the quality of the prenatal fetal anatomic survey and certain aspects of prenatal diagnostic screening programs are significantly limited. The net effect is that among obese gravidae, the increased risk of fetal anomalies is further offset by a concomitant diminished ability to sonographically detect such malformations in the prenatal interval. The purpose of this summary review is to systematically examine the evidence suggesting an increased risk of fetal malformations in obese gravidae, the contributing role of diabetes, and the limitations of prenatal diagnostic and sonographic screening among this at-risk population.