The current understanding of cleft lip malformations.

Cleft lip with or without cleft palate is one of the most common congenital malformations. Epidemiology differentiates between cleft malformations connected with syndromes and the more common nonsyndromic forms not associated with other deformities. Although many syndromes with cleft lip with or without cleft palate are known, the majority of orofacial clefts are of the nonsyndromic form. These are known to be of multifactorial origin, with both environmental and genetic factors in their etiology, most of which remain to be fully investigated. Recent literature reveals that wide ethnical and racial variations in the occurrence of cleft lip and/or palate exist. The purpose of this overview is to show the current standing of research in this field. Genetics, environmental factors, and morphogenesis of the primary and secondary palate in normal development and cleft malformations are especially emphasized.