Objectives: This study was undertaken to evaluate the accuracy of a single sonographic estimated fetal weight at 29-34 weeks' gestation with respect to birthweight determination in diabetic pregnancies.
Study design: A retrospective cohort study of 423 diabetic pregnancies with detailed fetal measurements at 29-34 weeks' gestation. Multivariate regression analysis was used to predict the birthweight. The percentiles of the estimated fetal weight and the calculated birthweight were compared with the actual birthweight percentile.
Results: The mean birthweight percentile at term was significantly higher than the estimated fetal weight percentile at 29-34 weeks' gestation in the women with poor glycemic control, but not the women with good control. On multivariate analysis, the estimated fetal weight, interval from ultrasound to delivery, hemoglobin A1C level, gestational age at ultrasound, and classification of glycemic control were independently associated with the birthweight. Both the estimated fetal weight and the calculated birthweight had a low sensitivity and a low positive predictive value for predicting large-for-gestational-age infants.
Conclusion: Accelerated fetal growth is evident primarily in diabetic women with poor glycemic control. These fetuses cannot be identified by a single ultrasound examination at 29-34 weeks' gestation.