Generally speaking, the causes of harelip in children include the following. Firstly, it is caused by family genetic factors. If the child’s immediate family members, such as parents, have harelip, the child will often develop harelip under the effect of genetic genes. Secondly, it is caused by the mother of the child suffering from adverse factors in early pregnancy, for example, if the mother of the child suffers from rubella or measles or is exposed to radiation, as well as taking anti-tumor or antibiotic drugs during the first three months of pregnancy, it will often cause the child to develop deformities, resulting in harelip or even congenital heart disease.