Infant polydactyly is a congenital malformation of the hand, congenital malformation of the hand is produced for a number of reasons, specifically the following: 1, an extra finger is usually emanated, that is, the family may not have this hereditary disease, only in late pregnancy, produce genetic mutations or other reasons, produce polydactyly. According to research and literature, the cause of polydactyly is exposure to radiation during 4-8 weeks of pregnancy, taking amoxicillin during 4-8 weeks, smoking, staying up late, which is the cause of emanation; 2, hereditary, familial causes, such as parents have, or siblings have, or may even have non-immediate relatives. So probably the two causes, congenital hereditary and disseminated, are most likely to occur in small children with congenital polydactyly during the 4-8 weeks of pregnancy.