What spinal change occurring with pregnancy alters mobility?

The correct answer is 'Lordosis.' During pregnancy, the enlarging uterus places increased weight on the spine, causing an exaggerated inward curvature known as lordosis. This change alters mobility by shifting the center of gravity forward, leading to a compensatory change in posture. Scoliosis (choice A) is a sideways curvature of the spine, not typically associated with pregnancy. Kyphosis (choice B) is an exaggerated outward curvature of the spine, while ankylosing spondylitis (choice D) is a chronic inflammatory condition affecting the spine, neither of which are directly related to the spinal changes seen in pregnancy.