MEASUREMENT OF LIMB CIRCUMFERENCES WITH 3-DIMENSIONAL ULTRASOUND FOR FETAL WEIGHT ESTIMATION

A large number of formulae have been published for fetal weight estima tion. This study examines the possibility of using three-dimensional u ltrasound to measure the limb circumference. This technology provides us with the opportunity to visualize two simultaneous, orthogonal plan es, allowing the exact determination of the transverse plane at the mi d-point of the limb. A total of 157 patients were scanned in the week prior to delivery. The following variables were measured in 154 fetuse s: biparietal diameter, head circumference, transverse abdominal diame ter, abdominal circumference, femur length, thigh circumference and ar m circumference. The whole population was split into three subgroups a ccording to the abdominal circumference centile (< 10th centile, 10-90 th centile, and > 90th centile), because this single variable has the strongest correlation with neonatal weight (R = 0.901). With forward s tepwise multiple regression analysis, four models were elaborated, one for the whole population and one for each subgroup. The small-for-dat es fetuses need a targeted formula including only two variables, thigh circumference and femur length. Our data suggest that the thigh circu mference measurement improves the estimation for growth-retarded fetus es and that the arm circumference improves the weight prediction for t he others. The measurement of the two variables, made possible with th ree-dimensional ultrasound, has improved our results in fetal weight e stimation.