A cleft lip is a separation in the upper lip. A cleft palate is an opening in the roof of the mouth, which divides the mouth and nose. Clefts result from incomplete development of the lip and/or palate in the early weeks of pregnancy. It is during this time that the face is being formed. The lip and primary palate develop at 4 to 6 weeks of gestation, while the secondary palate develops at approximately nine weeks.

A cleft lip or cleft palate can be either unilateral (one-side only) or bilateral (both sides). A cleft can be either complete or incomplete. A complete palatal cleft involves both the primary and secondary palate, while an incomplete cleft involves the secondary palate only. A child may be born with either a cleft lip or cleft palate or both.

Genetics and environmental factors are both considered instrumental in causing clefts. Cleft parents are known to be predisposed having cleft children. But the main cause is attributed to the deficiency of Folic Acid during pregnancy. The other causes are radiation, pollution, nutritional deficiency etc.