The purpose of this study was to evaluate growth velocities of various neonatal tissues in women with diabetes mellitus. We hypothesize that in large for gestational age (LGA) infants, insulin-sensitive tissue will demonstrate the greatest accelerated growth. Thirty-eight singleton pregnancies had prospective longitudinal ultrasound measurements of the fetal biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), femur length (FL), transcerebellar diameter (TCD), liver length, renal length, abdominal fat, and thigh fat in late pregnancy. At birth, neonatal body composition was estimated and anthropometric measurements were obtained. Twenty-four neonates were not large for gestational age (non-LGA) and 14 LGA based on birth weight percentile > or = 90 percentile. The fetal AC (P = 0.0006), liver length (P = 0.01), thigh fat (P = 0.02), and abdominal wall fat (P = 0.001) demonstrated accelerated growth velocity in LGA fetuses. At birth LGA infants had a 17% (P = 0.0001) increase in lean body mass, but a 99% (P = 0.0001) increase in fat mass compared with non-LGA infants. Using stepwise regression, abdominal wall fat accounted for 63% (P = 0.0001) of the variance in AC compared with 3% (P = 0.13) for liver length. In conclusion, ultrasound estimates of adiposity may potentially be a sensitive indicator of growth abnormalities in infants of diabetic women in late gestation.