The best time for pregnant women to take calcium supplements is from the 16th week of pregnancy to after delivery. In the early stage of pregnancy, many pregnant women will have early pregnancy reaction, nausea, vomiting and other physical discomfort, serious cases will lead to pregnant women can not eat. Taking calcium tablets during this period will aggravate gastrointestinal discomfort, and it is difficult to be absorbed effectively. Therefore, it is best to start calcium supplementation only after the early pregnancy reaction disappears and the appetite increases. Generally speaking, at 16 weeks of pregnancy, most pregnant women’s early pregnancy reaction has disappeared or reduced. And at this time with the gradual development and growth of the fetus, the calcium demand of pregnant women is also increasing, so it is better to start supplementing calcium at this time, and continue to supplement until after delivery. At about 16 weeks of pregnancy, in addition to calcium supplementation, you should also pay attention to the usual reasonable diet, increase calcium-rich foods in the diet, such as dairy products and animal foods. If you want to take calcium preparations for calcium supplementation, it is recommended to do so under the guidance of a doctor to avoid adverse effects on the fetus.