Mid-trimester serum relaxin concentrations and post-partum pelvic floor dysfunction

Objectives. To compare mid-trimester serum relaxin concentration (SRC) in primiparous women with or without pelvic floor dysfunction (PFD - stress urinary incontinence (SUI), genital prolapse). Design. Nested observational cohort study. Setting. Urogynecology clinic of affiliated University hospital. Population. Primiparous women one to four years post-partum, who had, at time of index pregnancy, participated in a prospective observational study looking at mid-trimester serum relaxin and preterm delivery. Methods. Relaxin had been obtained during the index pregnancy at 24 and 28 weeks. Primiparous women who had not given birth to a subsequent child were contacted and asked to return for a single visit assessing pelvic floor function. Main outcome measures. Pelvic Organ Prolapse Quantification system (POPQ) and Urogenital Distress Inventory (UDI-6). Results. Fifty women participated, of whom 40 delivered vaginally. Seventeen (34%) women had prolapse and 23 (46%) had stress incontinence. Relaxin was slightly higher (not significantly) in women with PFD than in those without. Relaxin concentration declined significantly more rapidly from 24 to 28 weeks in incontinent women, after adjusting for baseline and obstetrical factors. Conclusions. In contrast to previous reports, mid-gestation relaxin tended to be higher and fall significantly faster in women with PFD. Acknowledging relaxin's effects on collagen turnover, our findings explore the association between childbirth and PFD.