Published on August 22, 2012
Anatomical and physiological changes during pregnancy change the biomechanical and musculoskeletal system which can cause low back pain. The most obvious is weight gain. Increased weight in pregnancy can significantly increase compressive forces to lumbar spinal joints, hips and knees. Each pound can cause approximately 5 pounds more pressure to these joints.
Because most of the weight gained is located in the lower abdomen, pregnant women typically develop an accentuated lumbar lordosis (curvature in the lower back), which contributes to the very high prevalence of low back pain. Balance may be affected by changes in posture, predisposing pregnant women to loss of balance and increased risk of falling.
Another important musculoskeletal change during pregnancy (particularly the third trimester) is an increase in ligament laxity, leading to increased risk of joint instability. This increased laxity is caused by elevated hormonal levels, specifically estrogen and relaxin. The effects of these hormones is particularly prevalent in the pelvic region – the area of the body which must adapt the most to successfully deliver a baby – contributing to incidence of low back and pelvic pain. Overall, this change in joint laxity can
predispose pregnant women to increased incidence of strains and sprains.