Cleft lip and palate may occur as part of an underlying syndrome or be an isolated birth defect. A cleft lip is the result of the lip not “fusing” together during the first few months of foetal development. This often includes the separation of the upper gum line. A cleft palate, which also occurs during the first few months of foetal development, is a separation in the roof of the mouth caused by the sides of the palate not completely fusing one another. The severity of cleft lip and cleft palate can vary. A baby can be born with just a cleft lip, just a cleft palate, or both a cleft lip and palate. The clefts are classified as unilateral or bilateral. A unilateral cleft lip or palate affects just one side of the mouth. A bilateral cleft lip or palate affects both sides of the mouth.