Association between parity and the risk for urinary incontinence in women: A meta-analysis of case–control and cohort studies

Urinary incontinence (UI) is a common complaint for adult female. Cross-sectional studies suggested parity may link with UI, but the association between them was not well-established. We conducted a meta-analysis to investigate the association between parity and UI. Medline and Embase were searched for eligible case–control and cohort studies about parity and UI. Two authors screened the literature and extracted the data independently. Odds ratio (OR) was used as the measure of the effect of parity on UI. We pooled the ORs of different number of parity by a random-effect model. Subgroup analysis was conducted by a subtype of UI. Sensitivity analysis was conducted to see whether the results were stable. Thirteen studies (8 cohorts and 5 case–controls) were included in our meta-analysis, with a total of 74,883 adult females. Our meta-analysis showed that compared with nulliparity, ORs of women with 1, 2, and ≥3 parity were 1.43 [95% confidence interval (95% CI): 0.90–2.28; I(2) = 81.4%; n = 4], 1.50 (95% CI: 1.02–2.20; I(2) = 82.5%; n = 4), and 1.58 (95% CI: 1.22–2.03; I(2) = 70.1%; n = 7) compared with nulliparity. The OR for any multiparity to nulliparity was 1.68 (95% CI: 1.39–2.03; I(2) = 0%; n = 4). Subgroup analysis showed that parity was associated with an increased risk of stress UI (OR = 2.32, 95% CI: 1.41–3.81; I(2) = 0%; n = 2; 1 compared with null parity) but not urgent UI; However, the definition of parity varies across studies and studies defined parity as delivery times showed higher pooled OR than those not. Sensitivity analysis showed our results were stable. Current evidence suggested that parity was associated with an increased risk of overall and stress UI but not urgency UI, though the definition of parity may differ. Higher parity may have a more significant effect on overall UI. Standardized definition of parity is needed.