As a baby develops during pregnancy, the cells on each side of the head grow to the centre and join up. This process defines the lips, nose and mouth.
A cleft lip occurs when the tissue doesn't completely meet in the centre. This creates in an opening in the upper lip, usually on one side only. Sometimes this is a small slit or a larger hole connecting into the nose. Children with a cleft lip also can have a cleft palate.
The roof of the mouth is called the palate. A cleft palate occurs when the tissue that makes up the roof of the mouth fails to grow together properly during pregnancy. This could affect the front and the back of the palate or only part of the palate.
Children with a cleft lip with or without a cleft palate or a cleft palate alone often have problems with feeding and speaking clearly and can have ear infections. They also might have hearing problems and problems with their teeth.
Cleft lip and some cleft palates can be detected during pregnancy by routine ultrasound, though some cleft palates are detected as the child grows.