Association of Biomechanical Changes and Weight Gain Throughout Pregnancy

Low back and posterior pelvic pain are common in pregnant females. Previous studies have
demonstrated disability and it is estimated that all women experience some degree of
musculoskeletal discomfort during pregnancy. Borg-Stein et. al. found 25% of pregnant
females have temporarily disabling symptoms.

There is demonstrated controversy over the mechanism of low back pain in pregnancy. The
biomechanical theory implies that the enlarging uterus causes the maternal center of gravity
to move anteriorly causing stress on the low back. Jensen et. al. demonstrated that weight
gain correlated with biomechanical changes. The changes were measured by weight gain in
segmental regions of the body and in principal moments of inertia from the sit to stand
movement. Literature does not demonstrate a specific correlation between weight gain and
the biomechanical changes of sway rate, lumbosacral angle and center of gravity. These
three measurements may have a correlating effect on the underlying cause of low back pain in
pregnant women.

This study aims to determine the correlation between weight gain of pregnant females and the
biomechanical changes of sway rate, lumbosacral angle and center of gravity. The change in
weight over the last two trimesters will be correlated with the sway rate, lumbosacral angle
and center of gravity. The degree of symptomatic low back pain as measured by the Oswestry
Low Back Pain Scale will also be correlated with the sway rate, lumbosacral angle and center
of gravity.