Cleft Lip and palate is the most common developmental problem that affects the maxillofacial area. Most of the time, it is due to factors that affects the environment of the developing fetus, causing non-fusion of various facial segment, resulting in a visible cleft. It can present with an isolated cleft lip, cleft lip and alveolus, isolated cleft palate, or a combined cleft lip and palate.

Hereditary cause of cleft lip and palate are rare. Most of the cases are probably due to environmental factors including maternal infection such as rubella, maternal consumption of drugs such as anticancer therapy, antiepileptic drugs, steroids, or duet to hazards of X-ray radiation, etc. It can also be due to malnutrition of the mother during pregnancy in some underdeveloped regions.

In Asia, it is recorded that one in every 600 to 700 babies is born with a cleft lip or palate. Most of the cases are found in poor or developing areas, with the proportion from Hong Kong being relatively very small.