Pain on both sides of the hip bone when sleeping in late pregnancy may be caused by the following reasons: 1. It may be caused by overworking the muscles around the hip joint. In late pregnancy, due to the heavy weight of the fetus and amniotic fluid, the patient has a heavier load on the front of the body. In order to maintain the balance of the body, some muscles on the back side of the body and the muscles of the hip will remain tense for a long time, which may lead to muscle fatigue here and cause pain. The pain is more pronounced when the patient sleeps, as the muscles have relaxed. 2. This condition may be caused by osteoporosis. This type of disease is often due to too rapid fetal growth, or inadequate maternal feeding and malnutrition, which in turn leads to calcium deficiency. When osteoporosis occurs, there may also be pain in these two areas.3. This condition may be caused by prolonged pressure. In the course of pregnancy, as the patient needs to stay on her side while sleeping or resting, then long-term pressure on both sides of the hip joint alternately may cause soft tissue inflammation here, which in turn causes pain.