Cleft lip with or without cleft palate (CL/P), and isolated cleft palate (CP), are among the most common birth defects, with a prevalence at birth that ranges between 1 in 500 and 1 in 1000. These estimates, however, vary widely according to gender and ethnicity. Native American Indians have the highest prevalence at birth, with 3.6 cases with CL/P per 1,000 births. Asians have the second highest prevalence with 2.1 per 1,000 Japanese and 1.7 per 1,000 Chinese infants being born with oral clefts. Gender seems to play a role in the etiology of oral clefts as well, since males predominate by a 2:1 ratio for CL/P and females predominate by a 3:2 ratio for CP.

The lip and palate openings are normally present in early fetal development. The lip usually closes by 5 to 6 weeks after conception, and the palate by 10 weeks. Failure to close these tissues results in a cleft...