Fetal malformations commonly detectable on obstetric ultrasound.

A review of 364 fetuses with a total of 570 malformations discovered on ultrasound throughout the Emanuel Hospital referral pattern from 1978 to 1987 was compared to a previous multicenter study of 50,282 children from 1959 to 1965 that found minor or major congenital malformations in 6.5% of children, for a rate of 8.8 malformations per 100 children. The comparison was made to determine which of the malformations reported in the earlier study were commonly detectable on obstetric ultrasound as performed throughout the referral area and to determine what the combined prevalence of those malformations was within the general population. For the comparison, the number of patients undergoing obstetric ultrasound throughout our referral area was estimated from the number of anencephalic fetuses found. The relative prevalences of all malformations in the two groups were then determined by extrapolation. The malformations commonly detectable on ultrasound according to that comparison were then assigned the prevalences obtained from the earlier clinical study. According to this analysis, 0.7-0.8% of fetuses have major malformations commonly detectable on ultrasound, for a rate of 1.2 malformations per 100 fetuses. That represents about 13% of all malformations and about 27% of major malformations. If cardiovascular abnormalities, cleft lip and clubfoot were usually detected, the rate of malformations considered commonly detectable would increase to 2.7 per 100 fetuses. That would represent about 31% of all malformations and about 63% of major ones.