Cleft lip and cleft palate are both birth defects of the mouth. The combination of cleft lip and cleft palate is one of the most common birth defects. Although research continues on specific causes of cleft lip and cleft palate, they may result from sporadic or inherited genetic mutations or from certain maternal environmental exposures (for example, from smoking) during pregnancy.
Both of these birth defects form early in fetal development and can occur independently of each other (isolated) or in combination.
Cleft lip is one or more splits (clefts) in the upper lip. Cleft lip can range from a small indentation in the lip to a split in the lip that may extend up into one or both nostrils. Cleft lip develops in about the sixth to eighth week of gestation, when structures in the upper jaw do not fuse properly and the upper lip does not completely merge. Sometimes the nasal cavity, palate, and upper teeth are also affected.
Cleft palate is an opening in the roof of the mouth that develops when the bones and tissues do not completely join during fetal growth, sometime between the seventh and twelfth weeks of gestation. The severity and type of cleft palate vary according to where the cleft occurs on the palate and whether all the layers of the palate are affected. A mild form of cleft palate may not be visible because tissue covers the cleft. A complete cleft palate involves all layers of tissue of the soft palate, extends to and includes the hard palate, and may continue to the lip and nose. Sometimes problems linked with cleft palate also include deformities of the nasal cavities and/or the partition separating them (septum).
Cleft lip, whether isolated or occurring with cleft palate, is more common in males; isolated cleft palate occurs more often in females. Cleft palate-with or without cleft lip-is sometimes linked with other health conditions, such as fetal alcohol syndrome or chromosomal syndromes like trisomy 13 and 18.