背痛
Biomechanical factors of pregnancy shown to be associated with back pain include increased curvature of the lower back, or lumbar lordosis, to support the added weight on the abdomen. Also, a hormone called relaxin is released during pregnancy that softens the structural tissues in the pelvis and lower back to prepare for vaginal delivery. This softening and increased flexibility of the ligaments and joints in the lower back can result in pain. Back pain in pregnancy is often accompanied by radicular symptoms, suggested to be caused by the fetus pressing on the sacral plexus and lumbar plexus in the pelvis.