Some have suggested that women who are regular exercisers have a tighter pelvic floor and thereby have more difficulty during childbirth than non-exercising women. This study investigated whether women exercising before and during pregnancy have a narrower levator hiatus (LH) area than their sedentary counterparts. We also studied whether regular exercise at gestational week 37 influences delivery outcome. A cohort study of 274 nulliparous pregnant women assessed at mid-pregnancy and gestational week 37 by three-dimensional/four-dimensional transperineal ultrasonography of the LH area was conducted. Exercisers were defined as those exercising ≥30 min three times per week and non-exercisers as not exercising. Exercise data were collected via electronic questionnaire at mean gestational weeks 21 and 37. Labour and delivery outcomes were collected from the women’s electronic medical birth records. Differences between exercisers and non-exercisers were analysed using independent sample t test or χ(2) test. p Value was set to ≤0.05. At gestational week 37, exercisers had a significantly larger LH area than non-exercisers at rest and during PFM contraction (mean difference -1.6 cm(2) (95% CI -3.0 to -0.3), p=0.02 and -1.1 cm(2) (95% CI -2.0 to -0.1), p=0.04, respectively). No significant differences were observed between exercisers and non-exercisers at week 37 in any labour or delivery outcomes.
The results of this study did not support the hypothesis that women exercising regularly prior to or during pregnancy have a narrower LH area or more complicated childbirths than non-exercising women.