Serial ultrasonography to assess evolving fetal macrosomia. Studies in 23 pregnant diabetic women.

Serial ultrasound estimates of fetal biparietal diameter and abdominal circumference were used as differential indices of intrauterine growth of insulin-insensitive and insulin-sensitive structures, respectively, in 23 White's classes A to C diabetic women. Biparietal diameter in all fetuses conformed to growth patterns for fetuses of nondiabetic mothers. However, two patterns were noted for abdominal circumference. Normal increases occurred in 13 fetuses; in the remaining ten, growth of abdominal circumference exceeded upper normal limits from weeks 28 to 32 of gestation onward. This latter group with putative "accelerated somatic growth" in utero had more immunoreactive insulin in amniotic fluid, weighed more at birth, and had more subcutaneous fat. Serial differential ultrasonography may be useful for detecting evolving macrosomia in diabetic pregnancies, and fetal insulin or insulin-like principles may contribute to the macrosomia.