Generalized joint hypermobility and risk of pelvic girdle pain in pregnancy: does body mass index matter?

Background: Women with generalized joint hypermobility may be at increased risk of pregnancy-related pelvic girdle pain, but evidence is inconclusive. Objectives: In this prospective cohort study of 283 pregnant women in Norway, we aimed to study the association of generalized joint mobility with pelvic girdle pain, and to evaluate if pre-pregnancy body mass index was a modifier of the association. Methods: Generalized joint hypermobility was defined as a score of ≥5/9 positive tests on the Beighton score measured in early pregnancy. Primary outcome was evening pain intensity in gestation week 30, measured by a 100 mm visual analogue scale. We applied linear regression analyses to estimate age-adjusted unstandardized beta coefficients. Results: Evening pain intensity was similar among women with Beighton score ≥ 5/9 and women with Beighton score < 5/9 (age-adjusted mean difference 2.8 mm; 95% CI: -9.2 to 14.9 mm). Women with Beighton score ≥ 5/9 and pre-pregnancy body mass index ≥ 25 kg/m2, reported higher evening pain than women with Beighton score < 5/9 and pre-pregnancy body mass index <25 kg/m2 (age-adjusted mean difference 28.7 mm; 95% CI: 14.3-43.1 mm). Conclusions: Overall, evening pain intensity was similar among pregnant women with and without generalized joint hypermobility. However, women with a combination of generalized joint hypermobility and body mass index ≥25 kg/m2 reported higher evening pain compared to women with normal joint mobility and body mass index <25 kg/m2, suggesting that body mass index may modify the association. The estimates could be imprecise due to the small study sample, and our findings should be interpreted with caution.