Prediction of fetal macrosomia using sonographically measured abdominal subcutaneous tissue thickness

Purpose. We assessed the usefulness of sonographic measurement of abdominal subcutaneous tissue thickness in predicting fetal macrosomia (weight > 4,000 g). Methods. Abdominal subcutaneous tissue thickness was measured sonographically in 133 term fetuses. All studied fetuses were delivered within 72 hours after the measurements were taken. Results. One hundred thirteen fetuses were normal size, and 20 were macrosomic. The fetal abdominal subcutaneous tissue thickness ranged between 3 and 18 mm in all fetuses, with a mean measurement of 8.4 ± 2.7 mm (standard deviation). The mean tissue thickness differed significantly between normal and macrosomic fetuses (7.0 mm versus 12.4 mm, respectively; p < 0.0001). There was a significant positive correlation between the abdominal subcutaneous tissue thickness and the birth weight (r = 0.67, p < 0.0001). The negative predictive value for a range of cut-off points between 8 and 13 mm varied between 84.3% and 100% (for prevalence rates of macrosomia of 5-25%). However, the positive predictive value was less than 50% for cut-off values below 11 mm. Conclusions. Sonographic measurement of the subcutaneous tissue thickness of the fetal abdomen is useful for ruling out macrosomia.