According to Parents Magazine, pelvic bone pain during pregnancy can result from the growing baby and uterus. The body is quickly adapting to carrying a baby and must stretch to create adequate space in the pelvic region.
Some women experience pelvic bone pain due to ovarian cysts. Cysts commonly grow larger during pregnancy and are known to be painful, explains Parents Magazine. Round ligament pain typically begins after the second trimester and continues throughout the entire pregnancy. Parents Magazine describes round ligament pain as the uterus tilting and stretching; pain is especially noticeable while walking or getting up from a laying or sitting position.
During the third trimester, pain can be caused by the weight of the baby or Braxton Hicks contractions. Braxton Hicks contractions are intermittent and are not as painful as typical contractions. They are often caused by dehydration and can go away by lying down and drinking fluids. In other instances, pelvic bone pain can be caused by miscarriage, constipation, relaxed pelvic joints and urinary tract infections, states Parents Magazine. WebMD states that pelvic pain is often relieved by sleeping with a pillow between one's knees, resting as much as possible until the pain subsides and using a pregnancy girdle or pregnancy belt that helps lift the belly.