Final answer:
Pregnant women often experience back strain due to the expansion of the uterus and weight gain of the fetus, which shifts the center of gravity and alters posture, in addition to the release of the hormone relaxin that loosens ligaments supporting the spine.
Step-by-step explanation:
Why Pregnant Women Often Suffer from Back Strain Late in Their Pregnancy
Pregnant women frequently experience back strain during the later stages of pregnancy due to several physiological changes. One of the primary reasons is the expansion of the uterus and the increasing weight of the fetus. As the uterus grows, it takes up more space in the abdomen, thereby shifting the woman's center of gravity and altering her posture to maintain balance. This adjustment places additional strain on the back muscles as they work harder to support the new posture and weight distribution.
Furthermore, during the third trimester, the release of the hormone relaxin increases, which helps the pelvis to widen in preparation for childbirth. While this is an essential process, relaxin also causes the ligaments that support the spine to loosen, resulting in less stable joints and increased susceptibility to strain and pain.
The combined effects of a larger belly, weight gain, and loosened ligaments lead to the discomfort of back strain that many pregnant women experience. This discomfort can be exacerbated by factors such as pregnancy-induced swelling and increased pressure on the bladder, which lead to changes in walking style and posture.