Study design, materials and methods
The Swedish National Pregnancy Register covers 99.9% of deliveries and collects data from pregnancy to postpartum follow-up, including a digital survey since December 2020 (1).
Singleton primiparas ≥37 weeks with self-reported sPOP and UI at one year postpartum were identified. Women n= (29,434) completing validated POP and UI questions in the survey (2022–2024) were included; 23,759 had vaginal birth. sPOP and UI were defined as vaginal bulge symptoms and involuntary urine loss, respectively, occurring 1–3 times per month, 1–3 per week, or daily.
Statistical analyses were performed using SPSS v29. Prevalence of sPOP and UI, including isolated and concomitant conditions, was presented as n (%). Two outcomes were defined: (1) sPOP irrespective of UI; (2) concomitant sPOP and UI. In analyses of concomitant conditions, women with isolated sPOP or UI were excluded, and the outcome was both conditions versus neither.
Logistic regression was used to estimate associations between outcomes and risk factors. Model 1 included mode of delivery (vaginal vs cesarean section (CS)), maternal age (≥35 years), obesity (BMI ≥30 kg/m²), birth weight (≥4000 g), and head circumference (≥35 cm). Model 2, restricted to vaginal births, included vacuum extraction (VE), fetal presentation, length of active second stage (0–30, 31–59, ≥60 min), episiotomy, and perineal tears, adjusted for maternal and fetal characteristics. Odds ratios (OR) with 95% confidence intervals (CI) were calculated; p<0.05 was considered significant.
Results
The overall prevalence of sPOP was 11.6% (3,422/29,434), and 4.5% reported both sPOP and UI (1,325/29,434). sPOP was more common after vaginal birth than after CS (13.5% vs 3.8%; crude OR 3.92, 95% CI 3.41–4.51). A similar pattern was observed for both isolated and concomitant conditions (Fig 1).
In multivariable analyses, vaginal birth was associated with fourfold higher odds of sPOP compared with CS (adjusted OR 4.10, 95% CI 3.55–4.73), with stronger association for concomitant sPOP and UI (adjusted OR 5.30, 95% CI 4.22–6.66). Older maternal age, higher birth weight, and larger head circumference were associated with increased odds of both outcomes, with larger effect sizes for concomitant conditions (Fig 2).
In analyses restricted to vaginal births, longer active second stage, episiotomy, older maternal age, higher birth weight, and larger head circumference were associated with both outcomes, whereas obesity and fetal malpresentation were associated only with concomitant sPOP and UI. Effect sizes were consistently larger for concomitant sPOP and UI. VE and perineal tears were not associated with either outcome (Fig 2).
Interpretation of results
Our results show that sPOP and concomitant sPOP with UI are common one year postpartum, with sPOP affecting more than one in ten women, contrasting with the assumption that sPOP typically occur decades after childbirth (2).
Vaginal birth was the strongest risk factor, with no difference between VE and spontaneous vaginal delivery, consistent with previous findings (3); however, in contrast to (3), longer active second stage was associated with gradually increased odds of both outcomes.
Larger fetal size and older maternal age were associated with higher odds of both sPOP and sPOP with concomitant UI. Given that the mean age at first birth in our nationwide cohort exceeds 30 years, reflecting the global increase in maternal age, healthcare may need to adapt to this trend. The absence of forceps in Sweden suggests that these associations may be even stronger in jurisdictions where forceps are still used.