Generally, it is recommended that pregnant women start taking calcium supplements from mid-pregnancy, i.e. around 14-19 weeks of pregnancy, but the details will depend on individual circumstances. In the early stages of pregnancy, there is usually no need for special calcium supplementation because the fetus is small and has a low calcium demand. With the onset of mid-pregnancy, the fetus grows faster and the pregnant woman is prone to calcium deficiency, which may manifest as twitching of both lower extremities, especially at night with painful twitching of both lower extremity gastrocnemius muscles. Calcium supplementation is recommended at this time, not only to prevent osteoporosis during pregnancy and postpartum lactation, but also to prevent hypertension during pregnancy. Usually, pregnant women should take a total of 1000-1200mg of calcium per day, with about 600mg available from the diet, and the rest needing additional supplementation. Pregnant women are advised to consume foods with high calcium content, such as milk, shrimp, meat, eggs, etc. It is also recommended to get more sunlight and choose calcium complex preparations containing vitamin D.