Accuracy of clinically estimated fetal weight in pregnancies complicated by diabetes mellitus and obesity

Objective To determine the accuracy of clinically estimated fetal weight (CEFW) in patients with gestational diabetes (GDM), pregestational diabetes (DM), and obesity. Study Design This is a retrospective analysis of Consortium of Safe Labor data. Subjects were classified into six groups: DM, DM and obese, GDM, GDM and obese, nondiabetic obese, and controls. The mean difference between birth weight (BW) and CEFW, the percent of accurate CEFW (defined as < 10% difference), and the sensitivity for identifying BW > 4,000 g and > 4,500 g were calculated for each group. Results The accuracy of CEFW in our population was 54.3 to 64.4% and was significantly lower in patients with DM and obesity and patients with obesity but not diabetes. When CEFW was analyzed in the >4,000-g and > 4,500-g groups, its accuracy was 20 to 51% and 14 to 40%, respectively. CEFW overestimated BW more commonly in GDM, obese GDM, and obese groups. The sensitivity of CEFW for diagnosing BW > 4,000 g or > 4,500 g was 19.6% and 9.6%, respectively, and it improved in pregnancies complicated by diabetes. Conclusion CEFW is a poor predictor of macrosomia in pregnancies complicated by obesity and diabetes.