Embryology and epidemiology of cleft lip and palate.

Craniofacial anomalies, in particular cleft lip and palate, are major human birth defects with a worldwide frequency of 1 in 700 and substantial clinical impact. This article reviews the embryology of the face, lip, and palate to enhance the understanding of the pathogenesis of these lesions, with particular attention to the period of susceptibility during gestation, complexity, and the factors that may influence their development. It includes an overview of the prevalence and environmental and genetic causes of cleft lip-with or without cleft palate- and cleft palate.