Vitamin D deficiency in pregnant women may be caused by the increased demand of pregnant women and fetuses, and the failure of the mother to replenish in a timely manner, along with the manifestation of calcium deficiency. It is recommended that pregnant women have regular pregnancy tests and undergo treatment under the guidance of a doctor according to the test results. The main role of vitamin D is to promote the absorption of calcium and phosphorus by the mucous membrane cells of the small intestine, and it also has the role of promoting skin growth and regulating immune function. Vitamin D deficiency may cause symptoms such as leg cramps, back pain, loose teeth and easy sweating. In addition, vitamin D deficiency in pregnant women may also affect the bone development of the fetus, which is prone to late teething, cranial softening and even rickets after birth. Vitamin D can be supplemented through the following aspects: 1, medication: vitamin AD drops can be used as prescribed by the doctor, and oral calcium gluconate solution can be applied at the same time; 2, diet: eat more food containing vitamin D, such as sea fish, animal liver, eggs, milk, etc., usually pay attention to a reasonable mix of meat and vegetables in the diet, long time partial food or picky food can easily lead to vitamin or trace element deficiency, which is detrimental to the healthy growth of the fetus; 3, appropriate diet. 3, appropriate activities: it is recommended that pregnant women participate in outdoor aerobic exercise, through ultraviolet radiation, can also promote the transformation of vitamin D in the body, so as to prevent vitamin D deficiency.