During pregnancy, women routinely need to start calcium supplementation as soon as 4 months after pregnancy due to the needs of fetal growth and development. There is no best time to take calcium supplements after delivery because the mother needs to nurse her baby. Mothers who breastfeed after childbirth must ensure adequate calcium intake, and mothers who exclusively breastfeed excrete a certain amount of calcium from their milk every day. If the calcium intake is not sufficient, the calcium in the mother’s own bones must be used to meet the calcium in her milk. Therefore, it is recommended to continue to supplement calcium from the fourth month of pregnancy to meet the needs of the fetus and oneself, and to continue to supplement calcium after delivery to prevent the growth and development of the baby from being affected by calcium deficiency. It is recommended to take calcium supplements from the 4th trimester onwards to meet the needs of the fetus and the baby.