Abstract
OBJECTIVE: The objective was to estimate the effect of vaginal childbirth and other obstetric exposures on pelvic muscle strength 6-11 years after delivery and to investigate the relationship between pelvic muscle strength and pelvic floor disorders. METHODS: Among 666 parous women, pelvic muscle strength was measured with a perineometer 6-11 years after delivery. Obstetric exposures were classified by review of hospital records. Pelvic floor outcomes, including stress incontinence, overactive bladder, anal incontinence, and prolapse symptoms, were assessed with a validated questionnaire. Pelvic organ support was assessed using the Pelvic Organ Prolapse Quantification system. Kruskal-Wallis tests were used to estimate the univariable associations of obstetric exposures and pelvic floor outcomes with peak muscle strength. Stepwise multivariable linear regression models were used to estimate the association between obstetric exposures and muscle strength. RESULTS: In comparison with women who delivered all of their children by cesarean, peak muscle strength and duration of contraction were reduced among women with a history of vaginal delivery (39 compared with 29 cm H2O, P<.001). Pelvic muscle strength was further reduced after history of forceps delivery (17 cm H2O, P<.001). After vaginal delivery, reduced pelvic muscle strength was associated with symptoms of anal incontinence (P=.028) and pelvic organ prolapse on examination (P=.025); these associations were not observed among those who had delivered exclusively by cesarean. CONCLUSION: Pelvic muscle strength almost a decade after childbirth is affected by vaginal delivery and by forceps delivery. Although statistically significant, some of the differences observed were small in magnitude. LEVEL OF EVIDENCE: II.