One in every 700 births results in a cleft lip and/or palate. Many of these congenital deformities occur in families that have no history of clefts. While it is known how cleft deformities occur, it is seldom known why.
A cleft lip is a separation of the two sides of the lip. The separation often includes the bones of the upper jaw and/or upper gum. A cleft palate is an opening in the roof of the mouth in which the two sides of the palate did not fuse, or join together, as the unborn baby was developing. Cleft lip and cleft palate can occur on one side (unilateral cleft lip and/or palate), or on both sides (bilateral cleft lip and/or palate). Because the lip and the palate develop separately, it is possible for the child to have a cleft lip, a cleft palate, or both cleft lip and cleft palate.
Errors in articulation are common in cleft palate patients, especially those involving affricates and fricatives. Other errors include stop, glides, and nasal semivowels. Velopharyngeal incompetence is associated with an audible escape of air from the nose during production of pressure sounds and is termed nasal emission or snort. It is estimated that 75% of patients have velopharyngeal competence following primary cleft palate surgery, and this can be increased to 90-95% with directed secondary procedures.