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.