Calcium supplementation starts in the middle of pregnancy, around 16 weeks. At this time, the fetal bones begin to develop, and the calcium demand of pregnant women increases, requiring 1000-1200mg of calcium per day. The amount of calcium taken from the diet cannot meet the growth demand of the fetus, so additional supplementation is needed. Pregnant women can drink 500ml of milk a day, you can also eat the content of 500mg of calcium tablets, at the same time eat more calcium-rich foods, such as tofu, kelp, carp, soybeans, etc., but also pay attention to more sunshine, to promote the absorption of calcium. However, calcium supplementation should be in moderation, excessive intake is likely to cause calcification of the placenta, affecting the function of the placenta, if the function of the placenta is prematurely aging, which is detrimental to the fetus, the pregnancy must be terminated early.