MODEL RELEASED. Cleft lip. Image 2 of 2. Baby's face after surgery to repair a cleft, or hare, lip. This is a birth defect caused by a failure of the face to fuse together correctly during the embryonic stage of development. It affects about one in every 900 babies. Cleft lip is usually repaired by surgery when the baby is around three months old. There are generally no complications, although dental management and speech therapy may be necessary in some cases. See M350/283 for an image of the same baby before surgery to repair the cleft lip.