What is a cleft

During the normal development of a fetus there is always first a double lip, caw and palate fissure. Between week six and week nine of the pregnancy the different parts of the lip and the upper jaw grow towards each other and merge. Between week nine and week twelve of the pregnancy the palate is closing. If this does not happen, or not totally, there remains a gap, this is a cleft
(Riordan, Wambach. 2010).

The cleft may be involve only the lip, or may extent into the hard/soft palate.  The cleft may be unilateral (a fissure in the middle of the face, a bit on the right or left side) or bilateral (a fissure as well on the left as the right side of the middle) (Schisisteam Friesland, n.d.).