Auricular hypoplasia in one ear of newborns usually belongs to congenital auricular malformation, which can be mainly caused by genetic factors, drug damage and viral infection. 1. Genetic factor: genetic factor is the main factor of auricular hypoplasia, if the father or (and) mother of the newborn is the carrier of the gene of auricular malformation, there is a great possibility that the gene of auricular malformation will be passed on to the newborn, resulting in auricular hypoplasia of one ear of the newborn. 2. Drug damage: the mother has taken certain stimulating drugs during the fetal period, which leads to poor fetal growth and development, causing auricular malformation. 3. Viral infection: The newborn is infected by a virus during the embryonic formation process, which causes the fetal ear tissue to be underdeveloped, thus leading to the deformation of the auricle of one ear of the newborn. There may be other causes of auricular hypoplasia in one ear of newborns, so we suggest that you go to the hospital in time, complete the examination to clarify the cause of the disease, and then give targeted treatment or therapy under the guidance of the doctor.