Cleft lip is a birth defect that occurs when the tissues of the upper jaw and nose do not join as expected during fetal development, resulting in a split (cleft) in the lip. An incomplete cleft lip can range from a slight indentation to a notch in the upper lip on one or both sides. A complete cleft lip is a deep split in the lip that extends into one or both sides of the nose. Cleft lip can be corrected with one or more surgeries.