Anatomy
“Cleft” is used to describe any of the most common congenital oral-facial deformities. It is popularly referred to as “hare lip” or “hair lip”.
Oral-facial clefts appear around the lip or palate during the first four to eight weeks of pregnancy. During this time two lip and palate tissues normally fuse together from both sides of the tongue to form the upper lip and the hard and soft palate. If these tissues do not join properly, the result is a cleft, the type of which can vary. The most common types are cleft lip and palate (70%) and unilateral cleft lip (only 30%).