A Cleft lip is a congenital split or separation of the two sides of the upper lip. It usually appears as a small opening or gap in the skin in that area. Contrary to what the term would suggest, a cleft lip can extend up to the base of the nose and may even involve the bones of the upper jaw and even the upper gum. Less severe cleft lips may be only a small notch on one side of the lip, and more severe ones may involve a complete opening into the floor of the nasal cavity.
For some reason, cleft lips are more common on the left, but may also be bilateral. Cleft lips can even involve the alveolar margin, which is one of the two jaw ridges either on the roof of the mouth just above the upper teeth, or on the bottom of the mouth behind the lower teeth.
These areas contain the sockets for the teeth.
The occurrence of cleft lip is slightly more common than cleft palate. Also, when there is a cleft lip, there may also be a cleft palate as well. In a small percentage of cases, oral clefts are accompanied by cardiac abnormalities.
Many scientists and physicians who have studied Zofran (ondansetron) and birth defects have come to the conclusion that taking Zofran during early pregnancy significantly increases the risk of cleft lip, cleft palate, and cardiac defects.