Estimation of Fetal Birth Weight Using Ultra Sonographic Parameters

Abstract

One hundred antenatal patients were studied at term pregnancy at Gauhati Medical College, Guwahati, and
fetal birth weight estimation was done in utero Ultrasono-graphically. The parameters measured were
Abdominal Circumference (AC), Biparietal diameter (BPD) and Femur Length (FL), Fetal weight
prediction was done with Shepards formula using AC and BPD as well as Hadlocks formula using FL and
AC. The scan delivery interval was maintained at 72 hours or less. Results of both formulae were compared
with the actual fetal birthweight taken within 15 minutes of delivery. With Shepards formula, the predicted
fetal weight was within 100 gm of the actual fetal weight in 71% cases, within 150gm in 86% cases, within
200 gms in 93% cases and within 250 gms in 98%. With Hadlocks formula, the predicted birthweight was
within 100 gms of the actual fetal weight in 72% cases, within 150 gms in 83%, within 200 gms in 92%
cases and within 300 gms in 98%. The mean percent error calculated as Error % = Predicted weight - actual
weight divided by actual weight x 100 was 2.9% with Shepards formula and 3% with Hadlocks. These data
thus support a significant correlation between ultrasonographic estimation and actual fetal birth weight.
Key Words: Fetal birth weight, AC, BPD, FL