The bone pain in the lower body during late pregnancy may be caused by several reasons: 1. It may be caused by prolonged pressure. In the late stages of pregnancy, the amount of both fetal and amniotic fluid reaches its maximum. At this time, the patient may put a very heavy load on the pelvis and the bones of the lower body when standing upright, which may cause some joints around the pelvis, such as the pubic symphysis, to become mildly separated. In addition, it may cause very severe pressure on the bones of the pelvis, which then leads to pain. 2. It may be caused by insufficient exercise. Often seen in pregnant women, relatively poor physical condition before pregnancy and infrequent exercise can lead to insufficient strength of the muscles and ligaments around the pelvis. This is the case when the load is very heavy, it is easy to appear more loose, which leads to pain. 3, there may be due to osteoporosis caused by. In the late stages of pregnancy, as the fetus grows, there may be a calcium deficiency within the mother’s body, which then causes osteoporosis, which may cause bony pain here.