The causes of cleft lip and palate are not well understood, but are associated with changes in the baby’s genes. A tendency to the deformity may be inherited; the potential for the condition increases when it has occurred to members of the same family. Other factors that could affect genes leading to a cleft are viruses, some medications, the mother’s diet and environmental toxins. Recent studies have identified smoking and drinking alcohol during pregnancy as risk factors for a cleft lip and palate as well as other birth defects. In addition, diabetes has been shown to increase the chance of giving birth to a child with a cleft lip, with or without a cleft palate.