Ultrasound diagnosis of fetal macrosomia.

Macrosomic infants and their mothers are at increased risk for intrapartum injury and perinatal morbidity and mortality. This study investigates the effectiveness of individual ultrasound fetal measurements, ponderal indices and estimated fetal weight in the identification of macrosomia in 732 pregnant patients who underwent ultrasound examination within 7 days of delivery. All the indices evaluated were compared for accuracy in predicting birth weight. Statistical comparison revealed that estimated fetal weight predicted macrosomia better than single ultrasound parameters and ponderal indices. The formulae tested yielded an accuracy of 94% and a positive predictive value of 90%. Abdominal diameter and abdominal circumference values above the 90th centile correctly predicted macrosomia in 82% and 72% of cases, respectively. Fetal length showed a sensitivity of 61% with a predictive positive test of 41%. Femur length-to-abdominal circumference ratio detected macrosomia with a sensitivity of 80% and an accuracy of 82%. The other single ultrasound parameters and ponderal indices were significantly less indicative of macrosomia. The combined use of four indices (growth profile) did not improve the effectiveness of ultrasound in detecting fetal macrosomia. We conclude that the optimal prediction of fetal macrosomia is obtained from mathematical formulae for fetal weight estimation, based on several fetal measurement parameters and adjusted for different gestational periods.