The main causes of muscle cramps in pregnant women include calcium deficiency, cold stimulation, overweight, and poor posture. 1. calcium deficiency: because human leg muscle contraction and cell division require a large amount of calcium, and when pregnant women have insufficient daily calcium intake, it is easier to stimulate the leg nerve muscle excitability, resulting in muscle cramps in the lower limbs, i.e. muscle spasms; 2. cold stimulation: because pregnant women wear thin clothing or cold climate, it can cause muscle cramps in the distal limbs. 3. The cold climate and other circumstances, can cause the distal extremities of cold, which leads to muscle spasm pain; 3, overweight: some pregnant women in pregnancy weight growth is too fast, resulting in the lower limbs and waist and back muscle load increased. In the long run, this can cause muscle spasm due to overworked muscles in the above areas; 4, poor posture: pregnant women walking too much or standing for too long during pregnancy can increase the burden on the calf muscles, resulting in the accumulation of acidic metabolites in the local muscles, which can cause muscle spasm. In addition, pregnant women in the sleep period if a long time supine or prone, forcing the calf muscles in absolute relaxation for a long time, which is more likely to cause leg spasms. Therefore, pregnant women should take appropriate calcium supplements or dairy products during pregnancy, and pay attention to keeping warm, controlling diet and exercise. In addition, pregnant women can supplement their body with vitamin D through moderate sunlight, which will promote the absorption of calcium.