Calcium supplementation usually starts at 4 months of pregnancy. Starting from the 4th month of pregnancy, the fetus begins to accelerate its development and enlargement, the demand for calcium and other nutrients increases, and pregnant women need to start strengthening calcium supplementation. It is recommended that pregnant women drink 500ml of milk per day, with yogurt, cheese and other dairy products, and also need to take calcium supplements 400-800mg per day to meet the calcium needs of pregnant women and fetal development. According to the Dietary Guidelines for Chinese Residents, the daily calcium intake in early pregnancy is 800mg, 1000mg per day in mid-pregnancy, and 1200mg per day in late pregnancy, and according to the daily dietary habits of the Chinese people, the daily intake of calcium from food is about 400-700mg. Therefore, in the early stages of pregnancy can be to strengthen the calcium-rich diet, increase the intake of dairy products, increase outdoor activities, and to the middle and late stages of pregnancy, the amount of food intake can not meet the demand, you need to supplement calcium to avoid insufficient calcium intake.