We all start out life with a cleft lip and palate. During normal fetal development, between the sixth and eleventh week of pregnancy, the clefts in the lip and palate fuse together.
In babies born with cleft lip or cleft palate, one or both of these splits failed to fuse. Oral clefts are one of the most common birth defects.
Clefts in the lip can range from a tiny notch in the upper lip to a split that extends into the nose. A cleft palate can range from a small malformation which results in minimal problems to a large separation of the palate that interferes with eating, speaking, and even breathing.
Clefts are often referred to as unilateral, a split on one side, or bilateral, one split on each side.