Final answer:
The two major causes of changes in spinal alignment during pregnancy are increased shear forces due to the increased spinal curvature and the anterior pelvic tilt caused by weight distribution in the abdominal region.
Step-by-step explanation:
Causes of Changes in Spinal Alignment During Pregnancy
The two major causes of changes in spinal alignment during pregnancy are the increased curvature of the spinal column and an anterior shift in the line of gravity due to weight gain in the abdominal area.
The spinal column, which consists of 26 vertebral segments separated by discs and has a normal curvature for stability, can experience increased curvature during pregnancy.
This increase in curvature amplifies shearing forces on the lower vertebrae, which the discs are less capable of withstanding compared to compressional forces. Consequently, this results in an increased risk of back injury through ruptured discs, particularly the lumbosacral disc. The second cause, the shift in the line of gravity, leads to an anterior tilt of the pelvis and an enhanced lumbar curve, more commonly referred to as lordosis or swayback, which is highly associated with pregnancy in the later stages.