A cleft lip (CL) is a separation in the upper lip. A cleft palate (CP) is an opening in the roof of the mouth.
Clefts result from incomplete development of the lip and/or palate in the early weeks of pregnancy. During this time the face is being formed – the top and the two sides develop at the same time and grow towards each other, finally fusing in the middle. The lip and primary palate develop at 4 to 6 weeks of gestation, while the secondary palate develops at approximately nine weeks. Clefts affect approximately 1 in every 700 babies in Ireland.
In the instance of a cleft forming, the final closing does not fuse properly and an opening remains. The cause or causes for this failure to close are as yet not clearly understood, although research continues. Genetics and environmental factors are both considered instrumental in causing clefts.