Fetal mortality in oral cleft families: data from Indiana and Montreal.

Analysis of 418 sibships of oral cleft probands from Indiana, and 288 sibships from Montreal indicate that the incidence of fetal mortality is significantly greater in sibships of probands with cleft lip and cleft palate (CLP) as compared to that in sibships of probands with cleft lip (CL) alone. These findings support a multifactorial-two-threshold concept, according to which a lower level of liability results in clefting whereas a higher level of liability causes fetal deaths. They add confirmatory evidence in support of the authors' earlier work, utilizing data from two different sources.