The fetal harelip may form around the third month of gestation, but the exact time of formation depends on the etiology. Fetal harelip is a polygenic genetic lesion, and the incidence of the disease is related to the proximity of the bloodline. The fetus may develop cleft lip and palate during the third month of pregnancy due to viral infections or exposure to irritating chemicals, and the fetus may be triggered by smoking and alcohol abuse during pregnancy. In addition, the above mentioned factors can affect the differentiation of the fetal organ systems during the first 12 weeks of pregnancy. It is recommended that mothers within 3 months of pregnancy should eat foods rich in high quality protein, such as eggs, milk, fish, lean meat, etc., avoid exposure to harmful and radioactive substances, and have regular maternity checks.