Cleft lip and cleft palate is relatively common, occuring roughly once in 600 live births. The majority of these abnormalities are isolated occurrences, however there may be a positive family history. Some cases have been linked to maternal corticosteroid therapy.
The distribution of occurences of different types of cleft lip and/or cleft palate is approximately:
- cleft lip - a third
- cleft palate - a quarter
- cleft lip and palate - nearly half