The baby grows two teeth below and one tooth above may be a physiological phenomenon, or it may be caused by congenital missing milk teeth, lack of vitamin D and other reasons. 1. Babies start teething at 6 months of age and have all 20 milk teeth by the age of 2.5 years. The order of teething is related to many factors (e.g. genetics and nutritional status). It is very common for babies to have two teeth at the bottom and one at the top. As long as all the teeth come out within the normal period of eruption and are of good quality, there is no need for treatment. 2. Congenital loss of milk teeth can also cause babies to have two teeth at the bottom and one at the top. It is generally recommended to wear a denture as early as possible in childhood. 3. Vitamin D deficiency can also affect the normal development of the teeth, delaying teething and leading to malformations such as chicken breasts and square skulls. There may be other reasons for the baby to have two teeth below and one above, it is recommended to go to the hospital in time, complete the examination to clarify the cause of the disease, and then give targeted treatment or treatment under the guidance of the doctor.