Signs of damage in pelvic floor muscles at the end of pregnancy in rabbits.

INTRODUCTION AND HYPOTHESIS: Temporary effects to pelvic floor muscles are linked to impairments in micturition, particularly stress urinary incontinence (SUI), during pregnancy. We hypothesize that bulbospongiosus (Bsm) and pubococcygeus (Pcm) are differently damaged in primigravid and primiparous rabbits.

METHODS: Twenty-four rabbits allocated evenly (n = 6) into nulliparous, pregnant, and primiparous groups on postpartum days 3 (P3) and 20 (P20) were used to evaluate the myofiber cross-sectional area (CSA), β-glucuronidase activity, and anti-3-nitrotyrosine (anti-3-NTyr) immunoreactivity in Bsm and Pcm muscles. Appropriate statistical tests were done to determine significant differences among groups (P ≤ 0.05).

RESULTS: The average CSA of Bsm was not significantly different, albeit a high percentage of myofibers was enlarged in late-pregnant and primiparous rabbits on P3; β-glucuronidase activity and indirect parameter of muscle damage was also higher. These variables did not change in the Pcm muscle during the different reproductive stages. In contrast, the 3-NTyr immunoreactivity, an indicator of oxidative damage, was increased on P3 for Pcm myofibers and P20 for myofibers of both muscles.

CONCLUSIONS: Our findings demonstrate reliable signs of damage to Bsm and Pcm muscles in young female rabbits passing different reproductive stages. Damage to the Bsm muscles as detected at the end of pregnancy persisted after delivery. This was not the case for Pcm muscles, in which damage seems to appear after delivery.