If your eight-month-old baby is not teething, it may be caused by heredity or lack of calcium or missing milk teeth embryo. 1. Genetic factors: Although most babies will start teething around 4 to 6 months after birth, some babies are affected by genetic factors and may delay teething. 2. Calcium deficiency: eight-month-old babies who are not yet teething may be caused by calcium deficiency. At this time, you need to pay attention to observe whether the baby has a restless sleep, often unexplained crying and other manifestations. 3. missing milk teeth embryo: eight months baby because of congenital milk teeth embryo is missing can also lead to not be able to teeth. If your baby has not grown teeth in eight months, it is best to take your baby to the hospital to find out why.