Fetal mortality in oral cleft families (V): Studies of sporadic vs familial and pure vs syndromic clefts.

The frequencies of fetal deaths in sibships of oral cleft probands are analysed in relation to sporadic or familial clefts, and pure or syndromic clefts. In a study of 1823 pregnancies in 630 sibships of probands with CL(P), the frequency of fetal deaths was found to be increased, but not significantly, in the sporadic group as compared to the familial group of sibships from Indiana. However, such an increase was found to be significant in the Montreal data. The pooled data from both these centers also show a significant increase in the sporadic group. For CP, no such differences were found. Similar comparisons of fetal mortality in relation to pure and syndromic clefts indicated that the frequencies of fetal deaths were consistently elevated in sibships of probands with syndromic clefts with one exception, which is the Indiana CP group where the lowest frequency of fetal deaths was observed in the sibships. This group mostly consisted of sibships with solitary pregnancies. This may have been a result of early zygotic mortality in this group. Further data will be obtained to confirm this observation.