A Harelip is a
cleft (split) through the upper lip. It is called harelip because it looks like the hare's lip, which is split. Doctors do not know what causes harelip. Something prevents this section of the lip from growing together before the baby is born. Harelip may be single; that is, only one side of a lip may be cleft. Or both sides of a lip may be open.
Cleft palate, an opening in the roof of the mouth, often occurs with harelip. Sometimes a deformity of the nose also occurs. Doctors can successfully close these openings by means of surgical operations.