Level 1: Causes of low back pain in pregnant women Low back pain in pregnant women is a problem that many expectant mothers often encounter during pregnancy. There are many reasons, mainly including the following aspects: 1. Physiological changes: As the fetus grows and gradually becomes larger, it will put pressure on the surrounding organs and ligaments, causing waist discomfort. 2. Improper body posture: After pregnancy, due to factors such as the increase in weight and the forward shift of the center of gravity, it is easy to cause improper body posture.