Parity: a risk factor for decreased pelvic floor muscle strength and endurance in middle-aged women

The incidence of pelvic floor muscle (PFM) dysfunction increases rapidly with menopause and aging. Despite the raised magnitude and prevalence of pelvic floor disorders in middle-aged women, the risk factors underlying PFM dysfunction still remain to be identified. PFM function can be clinically measured as the maximum strength and endurance using manometry. The aim of this study was to evaluate PFM function in terms of strength and endurance by perineometer and to assess the risk factors that decrease PFM strength and endurance in middle-aged women.

This was a cross-sectional study. Overall, 125 parous women (age 40-60 years) completed the study. A questionnaire was used to collect information on several demographic and obstetric variables. The Peritron perineometer measured PFM strength and endurance. Multiple linear regression analysis was used to evaluate the effects of sociodemographic variables on PFM function.

Both average strength of PFMs and maximum muscle strength significantly reduced as the number of parity increased. Average and maximum strength of PFMs showed a significant difference between women with parities of two and one (β = -0.435, p < .001; β = -0.441, p < 0.001, respectively). Both were even more influenced in women with parity of three (β = -0.503, p < .001; β = -0.500, p < .001). However, PFM endurance did not decrease with increasing parity number until the parity of two; however, it decreased in women with parity of three (β = -0.302, p < 0.05).

Parity appeared to have a dominant influence on weakness of PFM, and strength was more significantly associated with parity than endurance in middle-aged women.