Sunken fontanels in newborns may be related to physiologic development, trauma, calcium deficiency or dehydration. 1. Physiological development: newborns are born with skull tissue not yet fully developed, there may be inter-bone gaps at the fontanel, which is the formation of physiological depression. 2. Trauma: the newborn’s fontanel has been impacted, due to the fragility of the skull and caused by the skull depression fracture. 3. Calcium deficiency: Long-term calcium deficiency in newborns can cause malnutritional cranial invagination, which is manifested as sunken fontanel, and is accompanied by slow reaction and developmental delay. 4. Dehydration: If the newborn has acute or chronic diarrhea, the long-term lack of water in the body, resulting in head depression, can be accompanied by poor skin elasticity, tear performance. Newborn fontanel depression, there may also be other reasons, it is recommended to go to the hospital in time to improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.