Generally, you need to take calcium tablets for 4 months of pregnancy. When you are 4 months pregnant, the fetus in your belly begins to calcify bones and teeth. In the eighth month of pregnancy, calcification accelerated until full term, and all deciduous teeth were formed, so extra calcium was needed in the fourth month of pregnancy. Pregnant mothers get calcium from food, which may not meet the needs of fetal bones and teeth growth and development, so the remaining calcium needs to be taken from calcium-containing foods and high-quality calcium tablets. After four months of pregnancy, pregnant women's daily demand for calcium has increased to 1000mg- 1200mg, so when they are four months pregnant, they can eat more calcium-containing foods and calcium tablets in moderation to get some calcium from them.