Upper cleft lip is a congenital malformation. The exact causes and pathogenesis of developmental and fusion disorders caused by this disease are not completely clear at present. According to a large number of experimental research and epidemiological investigation results, it may be caused by many factors rather than a single factor. Generally speaking, it can be divided into genetic factors and environmental factors, which are related to nutrition, heredity, infection, endocrine and other factors. The above are suggestions about what causes cleft lip. I hope it helps you, and I wish you health!