According to folklore, if a pregnant woman sees a hare, her child may be born with a harelip. This is nonsense, of course. While scientists still don't know the exact causes of cleft lip palate, they are getting closer to answers. Studies show that a combination of environmental and genetic (inherited) factors likely contribute to clefting. Current research indicates that primary causes of cleft lip and palate may include:
Genetics -- The risk of a cleft palate or cleft lip appears to be higher for babies whose siblings or parents have a cleft. A family history of clefting is viewed as one of the primary causes of cleft palate. Either parent can pass on the genetic material which leads to the development of a cleft. In some instances, babies will inherit a gene that makes them susceptible to clefting and then subsequent exposure to an environment factor will trigger the development of a cleft palate and/or cleft lip
Environment -- Exposure during early pregnancy to cigarette smoke, alcohol, some medications, illicit drugs, certain viruses and radiation from medical X-rays have been linked to clefting.
Nutrition -- Some researchers believe nutritional deficiencies in the mother, particularly a lack of folic acid, contribute to the development of cleft palates and cleft lips.
Race -- Clefting is most commonly seen in children of Asian, Latino and Native American descent. As a group, African-American children have the lowest incidence of cleft palate and lip.
Sex -- Boys are twice as likely to be born with a cleft lip, while girls are twice as likely to have a cleft palate.
Socio-economic Factors - Socio-economic factors are a promising area of study related to the causes of cleft palate. According to an article published by the American Dental Association, there appears to be a higher incidence of clefting related to teenage pregnancies and pregnancies in women older than 35.