Background: A difficult vaginal birth is known to be one of the causes of damage to the pelvic floor muscles. Prolonged second stage of labour is thought to be one of the implicating factors in this damage. If the muscles of the pelvic floor were hypertrophied in response to repetitive high impact training, then the 'suspected phenomenon' of a more difficult childbirth for very athletic women might be related to these muscles reducing pelvic floor compliance.
Aim: To document the muscle morphology of the pelvic floor using magnetic resonance imaging (MRI) in a group of nulliparous female athletes and to compare this to the findings in a similar group of age-matched nulliparous nonathletic women.
Methods: Static Magnetic Resonance (MR) imaging of the pelvic floor was performed with particular reference to the muscle morphology of levator ani and puborectalis. The cross-sectional area of the urogenital hiatus and the diameter of the bony pelvic outlet were also assessed.
Results: Significant differences in the cross-sectional area and width of the pelvic floor muscles, measured in the line of the anal canal, were found between the athletic group and the controls. There were no differences found between the two groups in the cross-sectional area of the urogenital hiatus, and the adequacy of the pelvic outlet was established with reference to normative data.
Conclusions: The differences shown in the pelvic floor muscles in the athletes and nonathletes provide a focus for further research into this area. This change might influence the function of the pelvic floor muscles in this subgroup of women.