What is a Cleft?

There is a fairly thorough explanation about the nature of cleft lips and palates on Wikipedia. Anna also gives a great explanation on her blog, "Cleft Notes," here. Essentially, a cleft is an opening that is left in the lip and/or the palate (roof of the mouth) when they fail to fuse normally during gestation. It occurs in about 1 in 500 to 750 births, but that number is closer to 1 in 450 in Utah. It is the most common birth defect. The exact cause is unknown, though the condition can be hereditary. It is generally said that some combination of genetics and environmental factors likely cause clefts.