Comparison of the Thickness of Lateral Abdominal Muscles Between Pregnant Women With and Without Low Back Pain

OBJECTIVES: To compare the thickness of the external oblique, internal oblique, and transversus abdominis muscles in pregnant subjects with and without low back pain (LBP) by the use of ultrasound to measure thickness. DESIGN: A case-control study. SETTING: An academic and tertiary care referral spine and sports medicine center. PARTICIPANTS: Fifty pregnant women with LBP during pregnancy and 54 pregnant control subjects. METHODS: Case and control subjects were matched for body mass index, gestational age, and number of previous pregnancies. A multiple linear regression model with adjustment for the gestational age of the subjects, as the potential confounder of the primary outcomes, was used to evaluate the association between LBP appearance and abdominal muscles thickness of the subjects. MAIN OUTCOME MEASURES: The thickness of lateral abdominal muscles was measured by ultrasound with the subject in a hook-lying position on the examination table. RESULTS: We found that there was no significant difference between pregnant subjects with and without LBP in terms of the thickness of external oblique, internal oblique, and transversus abdominis muscles. CONCLUSION: These findings suggest that other factors rather than the thickness of core stabilizing muscles are influential in the etiology of LBP during pregnancy. We hypothesize that enlargement of uterus during pregnancy might influence the thickness of the lateral abdominal muscles.