Calcium deficiency in newborns is mainly caused by the following reasons: First, it is caused by insufficient milk intake, because milk is the best source of calcium and the degree of absorption is better, and if the child has an adequate milk supply, he or she will not be deficient in calcium in general. Secondly, it is caused by vitamin D deficiency, because vitamin D can promote the absorption of calcium in the intestine, and if the child has vitamin D deficiency in the body, even if sufficient calcium is supplemented, it will lead to vitamin D deficiency rickets. Therefore, if a child has calcium deficiency, it can be judged from the following aspects: after calcium deficiency, the child will have more head sweating, easy to wake up and cry at night, and some children will have occipital baldness. If the calcium deficiency is severe, it will lead to convulsions, mainly with slight shaking of the arms and legs.