Intrapartum detection of a macrosomic fetus: clinical versus 8 sonographic models.

The purpose of this study was to determine whether clinical or sonographic models have 1) the highest accuracy in differentiating newborns with birth-weights > or = 4,000 g (macrosomia) versus < or = 3,999 g, and 2) among macrosomics which method of predicting birth-weight has the lowest percentage error. Prospectively, 602 consecutive parturients at term had a clinical estimate of birth-weight followed by sonographic measurement of fetal parts. The sonographic prediction of birth-weight was derived using 8 different models that utilize either 1 measurement or a combination of 2 to 4 parameters. The incidence of macrosomia was 11.1% (67 of 602). Analysis of ROC curves indicated that clinical predictions (w = 0.85) were significantly better than 4 of the 8 sonographic models. The mean standardized absolute error among macrosomic newborns is significantly lower when predictions are derived clinically (99 +/- 70 g/kg) than using 1 or 2 fetal parts. Sonographic assessment of birth-weight is not significantly more accurate in the detection of a macrosomic fetus than clinical predictions.