- Lip, cleft
- The presence of one or two vertical fissures (clefts) in the upper lip — cleft lip can be on one side only (unilateral) or on both sides (bilateral) — resulting from failure of the normal process of fusion of the lip to come to completion during embryonic life. Cleft lip is one of the most common physical birth defects. On the average, one baby per 1,000 is born with a cleft lip. The lip should normally fuse by 35 days of uterine age. Since failure of lip fusion can impair the subsequent closure of the palatal shelves, cleft lip often occurs in association with cleft palate. The cleft lip in this situation is the direct cause of the cleft palate. In dysmorphology (the study of birth defects), this disorder is called "cleft lip +/- (plus or minus) cleft palate." It is distinct from "cleft palate only." Cleft lip is corrected today by plastic surgery. The repair should be cosmetically good. The repair of a cleft palate can be more difficult. Cleft lip can be isolated or be part of a syndrome. By isolated is meant that the child is otherwise normal. Cleft lip is a part of many syndromes, for example, the trisomy 13 syndrome. If normal parents have an otherwise normal child with a cleft lip +/- cleft palate, there is an increased risk (4-5%) for their other children to be affected with this disorder. And if a second child has cleft lip, the risk for each subsequent sibling jumps to 9%.
Medical dictionary. 2011.