Twins With Clefts

Abstract

The concurrence of two experiments of nature, twins and congenital birth defects, provides a unique population for the elucidation of nature-nurture questions. Although the concurrence of twins with clefts is not common, their frequency in the aggregate of international reporting is sufficient to allow for meaningful studies.In a recent conference on the genetics of cleft lip and palate, Fraser (1968) summarized the state of knowledge regarding etiology. The following quotation from his report is pertinent to the present paper:1) In the majority of cases, cleft lip or cleft lip and palate [CL(P)] represents a quasi-continuous variant, or threshold character of multifactorial etiology. For cleft palate [CP] there is less convincing information;2) Observations on arch form, face shape, body asymmetries and developmental variables suggest that such variants may underly the predisposition to clefts;3) Twin studies may be useful in identifying the physiognomic factors predisposing to facial clefts.With these concepts in mind, we initiated an analysis of 19 twin pairs selected from the continuing longitudinal growth study which began at our Center in 1949 (Pruzansky and Lis, 1958).