The effect of a first vaginal delivery on the integrity of the pelvic floor musculature

Objective: To assess the specific effect of delivery of the first child on the integrity of the pelvic floor musculature. Design: A prospective study of two groups of females with no symptoms of urinary incontinence. Setting: Physiotherapy Department, Rotunda Lying In Hospital, Dublin. Subjects: Two groups of healthy female physiotherapists (age range 20-28 years) were recruited for the study: group I consisted of nulliparous; females (n = 10) and group 2 consisted of primiparous females who were 9-10 months post delivery (n = 10). Intervention and main outcome measures: Assessment of the pelvic floor musculature was performed by digital assessment, electromyography and perineometry. Results: For all data, the nulliparous group showed evidence of greater pelvic floor strength and endurance. Analysis of anterior and posterior electromyography data showed significantly stronger contractions in the nulliparous group (p = 0.0001 and 0.044). During a maximum contraction of the pelvic floor muscles, the anterior resting EMG activity increased by 9 +/- 6 muV (mean +/- SD) in the primiparous group compared with an increment of 22.3 +/- 4.74 muV in the nulliparous group. Posterior EMG resting activity increased by 19.7 +/- 7.65 muV (mean +/- SD) in the nulliparous group compared with 13.8 +/- 8.19 muV in the primiparous group. There were significant differences between the two groups for the four types of digital muscle assessment (p < 0.0013). In addition, there was a greater increase in perineometry readings in the nulliparous group (increment = 5.6 +/- 2.5, mean +/- SD) compared with the primiparous group (increment = 3.1 +/- 0.9; mean +/- SD). Conclusions: This study suggests that irrespective of lack of symptoms of urinary incontinence, it would appear advisable that all women should undertake a prescribed programme of pelvic floor rehabilitation exercises after childbirth.