The effect of the first vaginal birth on pelvic floor anatomy and dysfunction

Introduction and hypothesis First vaginal delivery severely interferes with pelvic floor anatomy and function. This study determines maternal and pregnancy-related risk factors for pelvic floor dysfunction (PFD), including urinary incontinence (UI), urgency, anal incontinence (AI), pelvic organ prolapse (POP) and levator ani muscle (LAM) avulsion. Methods This is a single-centre prospective observational cohort study on healthy women in their first singleton pregnancy. All underwent clinical and 3D transperineal ultrasound examination at 6 weeks and 12 months postpartum. Objective outcomes were POP-Q and presence or absence of LAM trauma. Functional outcomes were measured by the ICIQ-SF and PISQ 12. Multivariate regression was performed to determine birth and maternal habitus-related risk factors for UI, urgency, AI, dyspareunia, LAM avulsion and ballooning. Results Nine hundred eighty-seven women were included. Risk factors for UI were maternal age per year of age (OR: 1.09; 95% CI: 1.04-1.13; p = 0.0001) and BMI before pregnancy (OR: 1.08; 95% CI: 1.04-1.13; p = 0.001); for POP stage II+ maternal age (OR: 1.08; 95% CI: 1.08-1.14; p = 0.005). Avulsion was more likely after forceps (OR: 3.22; 95% CI:1.54-8.22; p = 0.015) but less likely after epidural analgesia (OR: 0.58; 95% CI: 0.37-0.90; p = 0.015) and grade I perineal rupture (OR: 0.50; 95% CI: 0.29-0.85; p = 0.012). Ballooning was more likely at increased maternal age (OR: 1.08; 95% CI: 1.02-1.13; p = 0.005), epidural (OR: 1.64; 95% CI: 1.06-2.55; p = 0.027) and grade I perineal rupture (OR: 1.79; 95% CI: 1.10-2.90; p = 0.018). Conclusion Though maternal characteristics at birth such as age or BMI increase the risk of PFD, labour and birth factors play a similarly important role. The most critical risk factor for MLA avulsion was forceps delivery, while an epidural had a protective effect.