A cleft palate is a birth defect that occurs when the roof of the mouth (palate) does not join together completely during pregnancy. The exact cause of cleft palate is unknown, but researchers believe that it is caused by a combination of genetic and environmental factors. Some children have a cleft palate because of changes in their genes, while others may develop it due to things the mother comes in contact with in her environment, or what the mother eats or drinks during pregnancy. Certain medications taken during pregnancy, such as antiseizure medications, acne treatment medications containing Accutane®, or methotrexate, a drug commonly used for treating cancer, arthritis, and psoriasis, may also increase the risk of cleft palate. Smoking cigarettes, using drugs, and/or drinking alcohol during pregnancy may also increase the risk of cleft palate.