Prediction of birth weight by ultrasound measurements of the fetus.

Fetal biparietal diameter, transverse thoracic diameter abdominal circumference and area were measured by ultrasound in 50 pregnant women at term not more than 48 hours before delivery. Multiple regressions correlating birth weight with all these parameters were obtained and estimated birth weight (calculated from the regressions) was compared with the actual birth weight. The error in prediction was under 200 g in 56%, under 300 g in 66% and under 400 g in 84% of patients when all fetal measurements were used. It was under 200 g in 48%, under 300 g in 66% and under 400 g in 74% when only the abdominal area was used; and it was under 200 g in 46%, under 300 g in 56% and under 400 g in 82% when the abdominal circumference alone was used. Biparietal diameter and transverse thoracic diameter alone were not useful in predicting birth weight.