Malformations and anomalies

Cleft lip and cleft palate are among the most common congenital abnormalities. They can occur separately but frequently are combined. Genetic as well as environmental factors are thought to play a role in their occurrence.
Cleft lip and cleft palate are classified according to their position with respect to the incisive fossa. There are three groups: (1) Cleft lip and clefts of the primary palate are anterior to the incisive fossa (anterior clefts); (2) Clefts of the secondary palate are behind  the incisive fossa (posterior clefts); (3) Anterior and posterior clefts are combined.