Cleft lip and palate is the prime facial disfigurement in children worldwide, with a quarter of a million born each year. It's a correctable birth defect that causes incomplete development of the structure of the mouth.

A cleft lip is a separation in the upper lip, and a cleft palate is an opening in the roof of the mouth. Clefts can occur on one side of the mouth (unilateral) or both sides, (bilateral) and can be in lip or palate or both.

The condition occurs between the fourth and sixth weeks of pregnancy as the facial structure of the foetus develops. Ireland has one of the highest incidences proportionally worldwide, with about 100 such babies born here each year.

The condition is genetic but not hereditary and probable causes include what plastic surgeon Doctor Michael Earley calls "a Celtic gene", or drawing from a small gene pool through intermarriage practised in some developing world communities, and poor nutrition. These days the defect is treated routinely in the western world.