A sunken fontanelle can be caused by a lack of water in the body, or it can be caused by malnutrition due to improper feeding, which can also result in a sunken fontanelle, or it can be caused by infection with other disorders in the mother’s fetus. When the body loses more water, the cerebrospinal fluid in the skull and the body’s blood tissue exchange will be imbalanced, and the cerebrospinal fluid will also decrease, thus lowering the pressure, and the fontanelle will become sunken. If rehydration is not done in time, it may be dangerous. In addition, malnutrition caused by improper feeding may also cause fontanelle depression, so it is important to strengthen children’s nutrition in daily life.