Craniofacial conditions, including cleft lip and palate, are congenital structural anomalies caused by atypical embryological development. Craniofacial differences are a result of interruption in embryologic growth between the 4th and 10th week of the developing embryo or fetus.

Clefts are described based on the structures involved (lip, alveolus, hard palate, soft palate), laterality (unilateral left, unilateral right, or bilateral), and severity (width and extent of structures involved). Clefts can be isolated (cleft lip only or cleft palate only), or they can occur in combination. They can be unilateral or bilateral, and they can be complete or incomplete.