Cleft

I believe that would be referring to a cleft palate, which is a deformity of the roof of the mouth / upper lip.

Here is the definition I found through Wikipedia:

Linky

I personally don't know how common it is, but I do know it's treatable with surgery, which is usually done soon after baby is born.

There is also a difference in how bad it is... but that link explains it better than I could !

My son has a cleft. There are a lot of variences such as single cleft double cleft and also lip and or palate which means either the lip is effected or both lip and palate. Its not to common, sometimes it runs in the family and other times like with us its just luck of the draw really. The plastic surgery these days is fantastic, people cant even tell Kobe has had one and my friends wee girl has just had her palate repaired last week and lip done a couple of months ago and you wouldnt even tell with her either. There are a few on going problems with it but certainly nothing major. if its just a general concern i woudnt worry because its not that common