RESUMO
Cleft lip is a congenital failure of union of embryogenic parts of the lip. It may be complete or incomplete, unilateral or bilateral, and may be accompanied by a cleft of the palate. There is a cleft of lip or palate in approximately one in every thousand births. The precise cause of cleft lip has not been definitely established; we simply know that it is a manifestation of incomplete embryonic development. It is interesting to note that cleft lip has occurred in one of a pair of identical twins, the other child is being entirely normal. Alcoholism, syphilis, poor heredity, malnutrition, etc., are often advacend as causative factors but their correlation with the defect has never been proved. Hereditary factor is in nineteen per cent of this series of cases. In our own series, we have been able to verify a hereditary tendency in only five per cent of the cases