Ultrasonic measurement of fetal body size. A randomized controlled trial.

A total of 745 Caucacian women were allocated at random between two groups, A and B, at the first antenatal visit. At the completion of the study, 341 patients in group A underwent a single ultrasonic measurement of fetal chest area between 32 and 36 weeks of gestation. The medical staff was not informed of these results. Three hundred and sixty-four patients in group B acted as controls. The percentage of clinically detected small-for-dates (S.F.D.'s) was low in both groups, A (36 per cent) and B (42 per cent). The ultrasonic detection rate of the clinically missed S.F.D.'s (group A) was 77 per cent. The clinical detection rate of large-for-dates (L.F.D.'s) was only 12 per cent in group A and 13 per cent in group B. The ultrasonic detection rate of the clinically unrecognized L.F.D.'s (group A) wa 60 per cent.