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Introduction
Urinary incontinence (UI) is defined as the involuntary leakage of urine [1]. During pregnancy, the growing uterus exerts increased pressure on the pelvic floor muscles (PFM), while hormonal changes can weaken their strength. These factors can lead to changes in the bladder neck and urethra, impairing urethral sphincter function [2].
Consequently, stress UI (SUI), characterized by urine leakage during physical exertion (e.g., exercise, sneezing, or coughing), is prevalent among pregnant women. SUI significantly impacts quality of life (QoL) in areas such as physical activity, travel, social interactions, and emotional well-being, affecting 54.3% of pregnant women [3]. Compared to those without SUI, pregnant women with the condition experience a lower QoL [4].
As pregnancy progresses, QoL tends to decline, particularly in women with UI. Moreover, frequent SUI is linked to decreased health-related QoL in both daily life and mental health, including postpartum depression [5].
Data from the Korean National Health Insurance Service-National Sample Cohort (2004–2013) reveals an association between UI and postpartum depression. Among 83,066 postpartum women, 5,393 (6.49%) experienced UI, and 691 (0.83%) developed postpartum depression. The latter was more common among women with UI, especially those aged 15–19, ≥40 years, with low income, or who had a cesarean section [6].
Despite the link between UI and reduced QoL, including depression, limited research exists on the prevalence and risk factors of UI in pregnant Korean women. This study aims to evaluate the prevalence of UI and its associated risk factors among this population.
Materials and methods
This study was approved by the Ethics Committee and conducted in accordance with the Declaration of Helsinki principles. Written informed consent was obtained from all participants, who were fully anonymized. Based on a 54.3% prevalence of SUI [3], a 95% confidence interval (z=1.96), a desired precision of 0.05, and an anticipated 20% non-response rate, the estimated sample size was over 457 participants.
This cross-sectional study was conducted between April and December 2023, involving consenting singleton pregnant women from three South Korean hospitals: Inje University Ilsan Paik Hospital, Daejeon Miz Women’s Hospital, and Ulsan Moms Women’s Hospital.
A two-part questionnaire was administered. The first section collected demographic data including age, occupation, education, gravidity, parity, delivery method, weight, height, pregnancy weight gain, alcohol and smoking consumption, and constipation status. The second section used the Korean version of the International Consultation on Incontinence Questionnaire-UI short form to assess UI. Participants were asked if they had experienced urine leakage to identify UI [7].
Pregnant women participated in the survey once per trimester (trimester 1: <14 weeks; trimester 2: 14–28 weeks, trimester 3: ≥28 weeks), with no requirement to complete all three surveys.
All participants were included except those meeting the exclusion criteria. These criteria included multiple pregnancies, incomplete surveys, childhood enuresis, pelvic surgery, pelvic organ prolapse, nocturnal enuresis, persistent UI, mental or psychiatric disorders, and uncontrolled diabetes.
Categorical variables were analyzed using the chi-square test. Univariate analysis identified potential risk factors for UI in pregnant women, followed by logistic regression analysis to assess their significance. Statistical significance was set at P<0.05.
Results
A total of 824 eligible pregnant women from three study centers participated, with a 40.2% (331/824) overall prenatal UI prevalence. SUI was most common (77.1%), followed by mixed UI (MUI) (16.9%) and urgency UI (UUI) (6.0%). UI episodes occurred at least once daily in 8.8% of participants, with more than a small leakage amount in 18.7% (Table 1).
Univariate analysis identified age, body mass index (BMI), gravidity, parity, previous delivery mode, gestational trimester, and pre-pregnancy drinking as potential predictors of prenatal UI (Table 2).
Multivariate regression analysis revealed vaginal delivery (adjusted odds ratio [aOR], 5.61; 95% confidence interval [CI], 1.40–22.50; P=0.015) and combined vaginal and cesarean delivery (aOR, 23.14; 95% CI, 1.77–302.74; P=0.017) as risk factors for UI. Additionally, the second (aOR, 1.99; 95% CI, 1.19–3.32; P=0.009) and third (aOR, 4.44; 95% CI, 2.65–7.40; P<0.001) trimesters were associated with increased UI risk. Conversely, pre-pregnancy drinking was a protective factor (aOR, 0.72; 95% CI, 0.53–0.99; P=0.046) (Table 3).
Discussion
UI was defined as any involuntary urine leakage [1]. Pregnant women are at a higher risk of UI, primarily due to temporary disruption to the pelvic floor caused by the growing fetus exerting pressure on the bladder [8]. Mechanical and hormonal changes during pregnancy can also weaken the PFM. Changes in relaxin levels during pregnancy may significantly influence SUI development. While relaxin is crucial for maintaining urinary continence during pregnancy, lower relaxin concentrations in late pregnancy have been correlated with a higher prevalence of SUI in the second and third trimesters [9].
UI often resolves postpartum; however, this condition can persist and become chronic in some women [10]. Women with a history of urinary leakage before or during pregnancy are at increased risk of developing postnatal UI [11]. Moreover, the risk of developing UI was significantly higher at 3 and 6 months postpartum among women who experienced UI as early as 20 weeks of gestation but received no treatment [12]. This underscores the importance of addressing and managing UI during pregnancy to prevent persistent postpartum incontinence.
This study’s 40.2% UI prevalence is similar to previous reports ranging from approximately 35% to 60.4% [13,14]. UI rates vary among different ethnic groups: 26% in Africa, 36% in the Middle East, 40% in East Asia, 43% in South Asia, and 45% in Europe/North America. A study in Karachi also reported a 45% UI prevalence [15].
SUI was the most common UI type in this study (77.1%), followed by MUI (16.9%), and UUI (6.0%). A recent report on Korean women found that 57.4% experienced lower urinary tract symptoms, with UI as the predominant symptom (45.8%), including SUI (33.6%), and UUI (12.2%) [16]. While SUI is the most prevalent UI type in pregnant women [4,17], Daly et al. [18] reported a higher MUI rate (58.8%) than SUI (37.2%) during pregnancy.
Univariate analysis identified age, BMI, gravidity, parity, previous delivery mode, gestational trimester, and pre-pregnancy drinking as factors significantly associated with UI during pregnancy. Multivariate regression analysis confirmed prior delivery mode as a primary risk factor, with vaginal delivery (aOR, 5.61; 95% CI, 1.40–22.50) and combined vaginal and cesarean delivery (aOR, 23.14; 95% CI, 1.77–302.74) significantly increasing UI risk. Additionally, the second (aOR, 1.99; 95% CI, 1.19–3.32) and third (aOR, 4.44; 95% CI, 2.65–7.40) trimesters were associated with higher UI risk. Pre-pregnancy drinking was identified as a protective factor (aOR, 0.72; 95% CI, 0.53–0.99) (Table 3).
Dinç [19] reported previous urinary tract infection, constipation, and gestational age as UI risk factors during pregnancy. UI rates varied by delivery mode: cesarean (19.7%), vaginal (54.9%), and vacuum (87.5%) [19]. UI prevalence was 4.4% and 23.7% in the first and third trimesters, respectively, and higher occurrence and severity was observed in older, overweight/obese, and unemployed women. Cesarean section reduced UI risk, while spontaneous tears, episiotomy, and high birth weight increased it. PFM training offered protection [20]. Post-vaginal delivery, PFM strength was associated with the cumulative incidence of pelvic organ prolapse and SUI [21].
Consistent with other studies, our findings highlight previous delivery mode as a primary UI risk factor during pregnancy. Vaginal delivery, with associated PFM stretching and potential injury, increases UI risk compared to cesarean section [22]. Advanced gestational age is another key risk factor, likely due to increased uterine pressure, fetal weight, and hormonal changes (e.g., increased progesterone, decreased relaxin, and decreased collagen levels) impacting PFM strength and function [23].
In our study, alcohol consumption before pregnancy was identified as a protective factor against prenatal UI (aOR, 0.72; 95% CI, 0.53–0.99; P=0.046). However, the relationship between overall alcohol consumption and UI was not significant [24,25].
A more in-depth investigation is needed to explore the potential protective effect of alcohol consumption before pregnancy, considering factors such as the amount consumed, drinking patterns, and type of alcohol. Such information was not available in the current study. A highly significant negative association was found between baseline beer intake and subsequent overactive bladder onset (P=0.001), with reduced risk across all levels of beer consumption compared to non- or infrequent beer drinkers. However, this association was attenuated after adjusting for total alcohol intake (g/day) (P=0.02) [26].
To the best of our knowledge, this is the first study reporting UI prevalence during pregnancy in South Korea. The results could be generalized through a larger, multicenter study. The higher UI rate in women with previous vaginal deliveries should be considered when pregnant women make delivery decisions. This study aimed for an adequate sample size and utilized a validated questionnaire across three centers, employing inferential statistics to identify UI risk factors.
Limitations include the study population being restricted to three antenatal clinics, potentially limiting generalizability to all Korean pregnant women. Additionally, UI diagnosis relied solely on questionnaire data, which may have reduced diagnostic accuracy. The study lacked detailed information on vaginal delivery (e.g., vacuum, labor duration, fetal, and newborn weight) and postpartum UI outcomes. As a cross-sectional study, causal relationships could not be established.
Despite limitations, this study provides valuable insights into UI prevalence and risk factors among pregnant Korean women, highlighting the need for prevention and management strategies. Further research is warranted to explore the association between UI and depression during pregnancy, as well as to investigate the impact of UI on postpartum and long-term outcomes. Psychological support for pregnant women with UI is crucial for improving QoL and pregnancy outcomes.
In conclusion, approximately 40% of Korean pregnant women experienced prenatal UI. Prior delivery mode and advanced gestational age were identified as significant risk factors. Further studies should include detailed information on delivery, labor, newborn weight, postpartum period, and long-term follow-up.
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