The results are from a study conducted in Norway

Regular exercisers at midpregnancy have stronger pelvic floor muscles than their sedentary counterpartsq a Norwegian study claims.

The results of the study conducted by a team at Akershus University Hospital (Oslo, Norway)q show that regular exercisers had statistically significant stronger (mean 6.4 cm H2O [95% confidence interval, 1.7–11.2]) and more enduring (mean 39.9 cm H2Osec [95% confidence interval, 42.2–75.7]) pelvic floor muscles. 

Only pelvic floor muscle strength remained statistically significant, when adjusting for possible confounders. Pelvic floor muscle strength and not regular general exercise was associated with urinary continence (adjusted B, –6.4 [95% confidence interval, –11.5 to –1.4]).

This is a cross-sectional study of 300 nulliparous pregnant women assessed at mean gestational week 20.9 (±1.4). The time period for inclusion was from January 2010 until April 2011.5
Inclusion criteria were being in their first ongoing singleton pregnancy and being able to understand Scandinavian languages. Exclusion criteria were multiple pregnancy or a previous miscarriage after gestational week 16. 

Regular exercisers were defined as women participating in general regular exercise training ≥30 minutes × 3 or more times per week. Women reporting that they never performed exercise were defined as nonexercisers.

The results were published in American Journal of Obstetrics and Gynecology. 

However, pelvic floor muscle strength and not regular general exercise was associated with urinary incontinence. There is a need for additional studies in elite athletes and women performing more strenuous exercise regimens, research team recommends.