Pelvic floor symptoms 1 year postpartum following forceps and vacuum deliveries: impact of levator ani muscle avulsion.

Abstract

Pelvic floor symptoms, such as vaginal bulge and stress urinary incontinence, are closely linked to vaginal delivery, especially assisted vaginal delivery. In addition, levator ani muscle avulsion, which may occur during vaginal delivery, increases the risk of pelvic floor dysfunction. However, the isolated effect of forceps or vacuum delivery in women with and without avulsion remains unclear. This study aimed to determine whether the presence of vaginal bulge symptoms and urinary incontinence 1 year after delivery differed between different vaginal delivery modes, accounting for levator ani muscle avulsion. In addition, this study aimed to assess the overall presence and bother of pelvic floor dysfunction across different delivery modes. This was a cross-sectional analysis of the Bergen Birth Study, a prospective observational cohort study comparing maternal and neonatal outcomes after forceps, vacuum, and spontaneous vaginal deliveries. Primiparous women with a singleton vaginal delivery at term between June 2021 and April 2023 were eligible. Exposure was defined as the delivery mode (spontaneous vaginal, vacuum, or forceps delivery). The women later underwent a transperineal ultrasound examination to assess levator ani muscle avulsion and answered the Pelvic Floor Distress Inventory-20 for grading of pelvic floor symptoms 9 to 12 months after delivery. The primary outcomes were the presence of vaginal bulge symptoms, stress urinary incontinence, and urge urinary incontinence on the Pelvic Floor Distress Inventory-20 questionnaire, with the degree of bother graded as "somewhat" or higher. Multiple logistic regression analysis was performed to compare the odds of vaginal bulge symptoms, stress urinary incontinence, and urge urinary incontinence between different modes of delivery. Age, body mass index, and self-reported prepregnancy urinary dysfunction were adjusted for as potential confounders. Nonparametric tests were used to compare the Pelvic Floor Distress Inventory-20 sum score between different delivery modes. In this study, 699 women were available for analysis, 238 had forceps delivery, 238 had vacuum delivery, and 223 had spontaneous vaginal delivery. Moreover, 142 of 699 women (20.3%) had levator ani muscle avulsion. Vaginal bulge symptoms were present in 10 (4.5%), 19 (8.0%), and 37 (15.6%) women after spontaneous, vacuum-assisted, and forceps-assisted deliveries, respectively. Women who underwent forceps delivery had an adjusted odds ratio of 3.21 (95% confidence interval, 1.56-7.14) of reporting bulge symptoms 1 year after delivery compared with those who underwent spontaneous delivery and an adjusted odds ratio of 1.87 (95% confidence interval, 1.02-3.49) compared with those who underwent vacuum delivery. In contrast, vacuum delivery was not associated with bulge symptoms compared with spontaneous delivery (adjusted odds ratio, 1.74 [95% confidence interval, 0.80-4.02]). In the subgroup analysis of women with intact levator ani muscle, the difference between forceps delivery and vacuum delivery was not significant (adjusted odds ratio, 1.59 [95% confidence interval, 0.74-3.47]). No association was found between mode of delivery and stress or urge urinary incontinence. Levator ani muscle avulsion was associated with more bulge symptoms (adjusted odds ratio, 3.58 [95% confidence interval, 2.06-6.18]) and urge urinary incontinence (adjusted odds ratio, 2.00 [95% confidence interval, 1.11-3.51]). The median Pelvic Floor Distress Inventory-20 score was statistically higher in the forceps delivery group than in the vacuum delivery and spontaneous vaginal delivery groups (25.0 in the forceps delivery group vs 18.2 in the vacuum delivery group [P=.03] and 25.0 in the forceps delivery group vs 16.7 in the spontaneous vaginal delivery group [P=.02]). Forceps delivery increased the odds of vaginal bulge symptoms 1 year after delivery compared with both vacuum and spontaneous vaginal deliveries. In women with no levator ani muscle avulsion, no difference was observed between the instruments. A higher Pelvic Floor Distress Inventory-20 score indicates greater symptom burden after forceps delivery, which seems to be mediated by the presence of levator ani muscle avulsion.