If a pregnant woman sleeps on her left side during pregnancy, it may be due to the long time compression of the left leg, calcium deficiency, lower extremity venous thrombosis, etc. It is recommended to improve the symptoms by sleeping in a different direction, taking calcium supplement or anticoagulation therapy. 1. The left leg is compressed for a long time: if pregnant women sleep on the left side for a long time, it will have pressure on the left leg, in this case, it is recommended not to keep a sleeping position, you can change the direction of sleep, in order to improve the symptom of leg soreness. 2. Calcium deficiency: Calcium deficiency in pregnant women can easily cause sore legs and leg cramps, in this case, it is recommended that pregnant women take calcium supplements under the guidance of the doctor. 3. Lower extremity venous thrombosis: During pregnancy, the blood of pregnant women is in a state of high coagulation, and if they do not exercise for a long time or press on a certain area for a long time, it may lead to poor blood circulation, thus forming blood clots. Once this happens, it is recommended to consult a doctor in time for proper anticoagulation treatment under the doctor’s guidance. Sleeping on the left side of the leg during pregnancy may also be caused by other reasons, it is recommended to go to the regular hospital in time to avoid adverse consequences. Pregnant women during pregnancy should be appropriate exercise, regular maternity checkups, found abnormalities should be timely medical attention.