Circulating levels of relaxin are normal in pregnant women with pelvic pain.

OBJECTIVE: The hormone relaxin induces loosening of the pelvic ligaments and joints in several species. Previous studies have suggested a similar role for relaxin during human pregnancy. Furthermore, a correlation has been noted between high circulating levels of this hormone and severe pelvic pain in pregnant women. The present study was designed to evaluate whether serum relaxin concentrations were elevated in pregnant women with clear subjective and objective evidence of pain attributable to relaxation of the pelvic ligaments. STUDY DESIGN: Serum relaxin was measured at week 33 of gestation in 455 pregnant women with clearly defined pain in their pelvic joints and 455 normal pregnant controls matched for age and parity. All participants underwent an examination consisting of a structured questionnaire and fifteen specific tests for pelvic joint pain. The group with pain was further subdivided into four subgroups with different levels of disability and prognosis. Relaxin concentrations were measured using enzyme-linked immunoassay. RESULTS: There was no difference in serum relaxin concentration between the control and study group, nor between the subgroups of women with pelvic pain. CONCLUSION: We failed to confirm an earlier claim that circulating relaxin levels are related to pelvic girdle pain in pregnant women.