Urinary incontinence (UI) is common in the postpartum period; however, most studies focus on the early postpartum period and assess prevalence at only one or two time-points, with significant variation in the literature regarding estimates of UI prevalence in the later postpartum period [1]. The aim of this study was to estimate prevalence of UI across the 24 months after delivery in a nationally representative, contemporary population of postpartum individuals. We hypothesized that UI would be highly prevalent when women were asked explicitly regarding symptoms. Our secondary aim was to identify risk factors for UI in the first 24 months postpartum.

The National Health and Nutrition Examination Survey (NHANES; 2011-2018), a program of the National Center for Health Statistics, was used to assemble a cross-sectional, population-based sample for this study. This sample was limited to parous individuals who reported a vaginal or cesarean delivery within the prior 24 months, and who were not currently pregnant. Bivariable analysis of the population by incontinence status was performed to evaluate differences in baseline characteristics between postpartum women with and without incontinence. A bivariable linear regression was performed to assess for a relationship between months since delivery and presence of UI symptoms. Multivariable logistic regression was used to estimate adjusted odds (aOR) of UI associated with exposures of interest.

560 parous women at 24 months or fewer postpartum were included in the sample. Given the NHANES survey design and weighting procedures, this can be extrapolated to represent 6,556,142 women in the U.S. population [2]. 229 individuals (43.5%, weighted prevalence) reported any UI. Stress UI was most common (37.8%), and most women (82.8%) experienced mild symptoms. There was no significant change in prevalence of UI across the 24 months following delivery (R2=0.004, p=0.20). Individuals with postpartum UI tended to be older (30.3 ±0.5 versus 28.8 ±0.5 years, p=0.04) and had higher BMI (31.1 ±0.6 versus 28.9 ±0.6, p=0.009). In multivariable analysis, odds of postpartum UI were higher for women who had a prior vaginal delivery (aOR 2.0, 95% CI: 1.3-3.3), prior delivery of a baby weighing 9lbs or more (aOR 2.5, 95% CI: 1.3-4.8), or who reported current smoking (aOR 1.5, 95% CI: 1.0-2.3).

In this nationally representative American cohort of 560 women at 24 months or fewer postpartum, UI is prevalent with similar rates of UI reported by women across this postpartum period. Individuals with postpartum UI tended to be older and had higher BMI, while prior vaginal delivery, delivery of an infant weighing 9lbs or more, and current smoking were independently associated with increased odds of UI in a multivariable model. These results are consistent with risk factors for postpartum UI identified in prior studies. However, the persistently high prevalence of UI demonstrated in women across the first 24 months postpartum contrasts with reports that UI symptoms typically resolve over the months following delivery [3]. 
Limitations of this study include its observational design, without access to specialized instruments for assessment of UI type and severity, or objective measures of incontinence. Additionally, due to the nature of NHANES, we were unable to assess some established risk factors for postpartum UI, including incontinence before and during pregnancy. Strengths of this study include the use of the NHANES survey, which provides a nationally representative sample of community dwelling individuals, reducing sampling bias, while the combination of interviews and physical examinations may also reduce reporting bias regarding important factors such as BMI. Other strengths of this study include our assessment of UI across the first 24 months after delivery, and our use of a multivariable logistic regression model to estimate the association between proposed risk factors and incontinence.

Urinary incontinence is prevalent during the first two years postpartum, with relatively stable prevalence over this period. This high and enduring prevalence highlights the importance of screening for incontinence longitudinally during the postpartum period and beyond to promote patient education, support, and treatment.

Thom D, Rortveit G. Prevalence of postpartum urinary incontinence: a systematic review. Acta Obstet Gynecol. 2010;89:1511-1522.
Centers for Disease Control and Prevention (CDC). National Center for Health Statistics (NCHS). National Health and Nutrition Examination Survey Data. Hyattsville, MD: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, 2011-2018. https://wwwn.cdc.gov/nchs/nhanes/. Accessed 12 July 2022.
Milsom I, Gyhagen M. The prevalence of urinary incontinence. Climacteric. 2019;22(3):217-222.