Urinary incontinence (UI) has an effect on quality of life during the postpartum period.1,2 Fear of UI is one of the most common reasons for maternal demand for cesarean delivery.3,4 The muscle strength of the pelvic floor returns to the antepartum value 6–10 weeks postpartum in most women.5,6 However, UI symptoms after delivery do not resolve in the long term in some women.7,8 Studies have variously concluded that the prevalence of UI changed9 or did not change within 6 months or 1 year postpartum.10,11 A higher prevalence or incidence of UI has been observed in women who had a vaginal delivery than in women who underwent cesarean delivery.10–18 In contrast, a recent study found that vaginal delivery was not associated with postpartum UI.19 The long-term protective effect of cesarean delivery has not been determined.20 Validated and reliable questionnaires to evaluate UI, including severity and quality of life, are needed for postpartum evaluation.21 However, comparisons of UI severity and the effect on daily life between women who have had vaginal and cesarean deliveries are scarce.22
The long-term associations of delivery mode with UI and changes in UI over a continuous period are unclear or remain controversial, perhaps as a result of different methodologies, including variations in the definition of UI, measuring instruments used, measuring time points, and research design such as whether within-subject comparisons were used. The aims of this study were to examine self-reported UI including prevalence of UI type, UI severity, and effect of UI on daily life for three groups (all participants, vaginal delivery, and cesarean delivery); compare the data on UI between vaginal delivery and cesarean delivery groups; and evaluate the change in UI for the three groups from 3–5 days to 12 months, from 3–5 days to 3 months, and from 3 to 12 months after delivery.
MATERIALS AND METHODS
We used a prospective, five-time-point longitudinal design over the 1-year postpartum period. This study was one part of a follow-up study on women's health after childbirth that was reviewed and approved by the Research Ethics Committee of the National Taiwan University Hospital. The participants were recruited consecutively when they gave birth in a maternity unit at a large medical center in Taiwan between 2010 and 2011. The inclusion criteria were at least 18 year old and the ability to read traditional Chinese. The protocol was explained to each participant. Voluntary participation was emphasized, and privacy was assured. The participants were informed that they could terminate the follow-up at any time.
Urinary incontinence was measured by the Taiwanese version of the International Consultation on Incontinence Questionnaire–UI Short Form, which was translated from English and is a reliable and valid instrument for evaluating UI postpartum.23 The International Consultation on Incontinence Questionnaire–UI Short Form provides a sum score and was developed by the International Consultation on Incontinence Modular Questionnaire study group.24 Correlations between the International Consultation on Incontinence Questionnaire–UI Short Form score and urodynamic findings,25 between the International Consultation on Incontinence Questionnaire–UI Short Form and the 24-hour pad test,26 and between the International Consultation on Incontinence Questionnaire–UI Short Form and the 1-hour pad test have been verified.27 The International Consultation on Incontinence Questionnaire–UI Short Form comprises three scored items and one nonscored item and is easy to administer to assess the prevalence, severity, interference in daily life, and type of UI.24,28 The three International Consultation on Incontinence Questionnaire–UI Short Form scored items are: 1) How often do you leak urine? 2) How much urine do you usually leak? 3) Overall, how much does leaking urine interfere with your everyday life? The answers for the three items are summed with a minimum score of 0 and a maximum score of 21. Cutoff scores were set to 0=“no incontinence” and 1 or greater=“urinary incontinence.”29 Urinary incontinence severity for the summed scores of the three International Consultation on Incontinence Questionnaire–UI Short Form items was rated as (1–5), moderate (6–12), severe (13–18), or very severe (19–21).30 Scores on the third item of the International Consultation on Incontinence Questionnaire–UI Short Form represent the level of interference in daily life.
The one nonscored item of the International Consultation on Incontinence Questionnaire–UI Short Form (“When does urine leak?”) includes eight answers and is a self-diagnostic item to understand the participant’s perception of the cause and type of leakage. The perceived cause of leakage is a good indicator of the objectively proven cause of incontinence31 and therefore allows classifications of UI as stress, urge, or mixed UI.32 Urinary incontinence is categorized as stress urinary incontinence (SUI) if the woman has involuntary leakage on effort or exertion or on sneezing or cough. The classification of urge urinary incontinence (UUI) reflects a complaint of involuntary leakage accompanied by or immediately preceded by urgency. Mixed UI is chosen when the complaint is involuntary leakage associated with urgency and also with exertion, effort, sneezing, or coughing.32 An answer of “never” indicates no urine leakage. The answers “leaks before you can get to the toilet,” “leaks when you are asleep,” and “leaks when you have finished urinating and are dressed” were regarded as indicators of UUI. The answers “leaks when you cough or sneeze” and “leaks when you are physically active or exercising” were indicators of SUI. A combination of these answers indicating urge and SUI was regarded as an indicator of mixed UI, and answers “leaks for no obvious reason” and “leaks all the time” were assigned to “other” causes of UI.31
Descriptive analyses were used to identify the demographic characteristics of the participants who underwent vaginal and cesarean deliveries and the UI indices for all three groups at each time point postpartum. The UI indices included prevalence of any UI, UI type, UI severity, and the interference in daily life score. The SAS GENMOD procedure was applied for each of the following analyses using the generalized estimating equation to account for the repeated measure characteristic of longitudinal observations. The difference in UI prevalence at 3–5 days after birth between women who did not and those who completed five visits was tested by binary logistic analysis. Differences in demographic variables and comparisons of UI indices between the vaginal delivery and cesarean delivery groups were assessed by analysis of variance for continuous variables, logistic analysis for binary variables, and cumulative logistic analysis for categorical variables. Statistically significant differences in demographic variables between vaginal and cesarean deliveries were considered covariates for the assessment of differences in delivery method for each of the UI indices. After adjusting for age, body mass index (BMI, calculated as weight (kg)/[height (m)]2), and newborn birth weight, trends in the changes in UI from 3–5 days to 12 months, from 3–5 days to 3 months, and from 3 to 12 months postpartum were tested by multiple regression and logistic regression with the generalized estimating equation option for continuous and binary variables, respectively. Generalized estimating equation regression models are appropriate for longitudinal analyses because they account for the correlation between repeated measures in an individual33 regardless of whether the measures are discrete or continuous outcomes, normal, or not normal distributions.34 A P value <.05 was considered significant. Statistical analyses were performed using SAS 9.3.
A total of 749 women were recruited, consented to participate, and completed a questionnaire that included demographic and obstetric characteristics and an evaluation of UI at 3–5 days after childbirth (baseline). Assessment of UI and related updated personal data were followed up in the waiting room while the women awaited a postnatal examination or by mail at 4–6 weeks and at 3, 6, and 12 months after delivery. A total of 419 women failed to complete the five visits. Forty-seven of 419 women were pregnant again during the investigating period. Thus, 330 women completed the UI questionnaire over five visits (Fig. 1). We found no significant differences in the prevalence of stress, urge, mixed, or other UI and no difference in UI severity at baseline between the women who did not (n=419) and those who did complete the five visits (n=330) (P=.10–.80). The lack of a difference in these findings validated the longitudinal, within-subject design of the study to investigate the 330 participants who constituted the study sample.
Table 1 presents the baseline characteristics of the 141 (42.7%) and 189 (57.3%) women at 3–5 days after vaginal and cesarean delivery, respectively. Significant difference in age, BMI, and newborn birth weight were found between the vaginal delivery and cesarean delivery groups (all P<.05). These significant variables were used as covariates.
After adjusting for age, BMI, and newborn birth weight, the comparisons of UI in the vaginal delivery and cesarean delivery groups at each postpartum time are shown in Table 2 and Figures 2A–H. The prevalence of any type of UI after vaginal delivery was significantly higher than that for the cesarean delivery group at 4–6 weeks (P<.001), 3 months (P<.001), 6 months (P=.03), and 12 months (P<.001). Similarly, the prevalence of SUI at 4–6 weeks (P<.001), 3 months (P=.01), and 12 months (P=.01) and the prevalence of UUI at 4–6 weeks (P=.04), 3 months (P=.01), and 12 months (P=.03) were higher in the vaginal delivery than in the cesarean delivery group. The prevalence of mixed UI was higher in the vaginal group only at 4–6 weeks (P=.04). No significant difference in the prevalence of “other” UI type was found between the groups at any visit.
The prevalence of slight UI in the vaginal delivery group was significantly higher than that in the cesarean delivery group at 4–6 weeks and at 3 and 12 months postpartum (P<.001, P=.03, P<.001, respectively). Additionally, the prevalence of moderate or severe UI at 3–5 days (P=.04), 4–6 weeks (P=.02), and 6 months (P=.04) and the score for interference in daily life at 3–5 days (P=.03) and 4–6 weeks (P=.01) were higher in the vaginal delivery group than in the cesarean delivery group.
After adjusting for covariates, the trends for changes in UI and interference in daily life are shown in Table 3. The prevalence of UI tended to increase significantly for any UI and for SUI in all participants (both P<.001) and in the vaginal delivery group (P=.02, P<.001, respectively) through the first year postpartum. The prevalence of slight UI tended to increase significantly for all participants and for the vaginal delivery group (both P=.02), and the score for interference with daily life tended to decrease for all participants (P=.04) and for the vaginal delivery group (P=.02) through the first year postpartum. No significant changes in any UI index were found for the cesarean delivery group through the first year postpartum.
The prevalence of any UI and SUI tended to decrease in the cesarean delivery group from 3–5 days to 3 months postpartum (P=.03, P=.050, respectively). The prevalence of moderate or severe UI and the score for interference with daily life decreased for all participants (both P<.001) and for the vaginal delivery group (P=.01, P<.001, respectively) from 3–5 days to 3 months postpartum. The prevalence of any UI and of SUI tended to increase in all three groups from 3 to 12 months postpartum (all P<.001) and the prevalence of slight UI tended to increase for all participants and for the vaginal delivery group from 3 to 12 months postpartum (both P=.02).
The prevalence of any UI across 1 year postpartum was 23.3–33.9% for all participants, 29.1–40.2% for vaginal delivery, and 14.2–25.5% for cesarean delivery. Stress urinary incontinence was the most prevalent postpartum among the different types of UI across the first year. Very severe UI was not found in the current study population. The prevalence of UI type, UI severity, and scores for interference in daily life for all delivery, vaginal delivery, and cesarean delivery at each of the five observation times are shown in Table 4 and Figures 2A–H.
This study presents a clear profile of the prevalence of any UI, types of UI, UI severity, and interference in daily life during the first year postpartum for all participants and for women who underwent vaginal delivery or a cesarean delivery. The prevalence of any UI in all participants was 23.3–33.9% during 12 months postpartum (Table 4). A previous longitudinal study found that the prevalence of any UI was 9.32–13.25% during 12 months postpartum,10 which was lower than the prevalence in our study at each time point. The differences may be the result of differences in the definition of UI, the measures used, population characteristics, or ethnicity.35,36 However, we found that the prevalence of UI within 1 year postpartum was highest at 12 months postpartum and lowest at 3 months postpartum, and these results are consistent with the findings of the other study.10
The vaginal delivery group had a significantly higher prevalence of any UI over the first year postpartum, which is consistent with the findings of a previous longitudinal study.10 Stress urinary incontinence was the most prevalent of all types of UI, which is consistent with previous studies.15,18 Women who underwent a vaginal delivery had a significantly higher prevalence of SUI and UUI at 4–6 weeks and at 3 and 12 months postpartum than did those who had a cesarean delivery. Some reports have concluded that vaginal delivery was negatively associated with postpartum SUI,22 but that prevalence of UUI was not different between groups.11,15,37 The prevalence of mixed UI was lowest among all types of UI, which was consistent with previous studies.11,15 Mode of delivery was not associated with the prevalence of mixed incontinence after 3 months postpartum, which was consistent with a previous report.11
The association between vaginal delivery and the higher prevalence of any UI, SUI, and UUI persisted to 1 year postpartum. However, moderate or severe UI persisted for just 6 months postpartum. No association between vaginal delivery and interference with daily life was observed after 6 weeks, which supports a previous study.22 Additionally, the prevalence of moderate or severe UI in the vaginal delivery group was higher than that in the cesarean delivery group at 3–5 days, perhaps because pelvic floor muscle strength is significantly reduced at 3–8 days after vaginal delivery, but this is not the case after cesarean delivery.6
Our study used within-subject comparison and statistical testing to determine that the prevalence of any UI and slight SUI tended to increase throughout the first year postpartum in all participants and in the vaginal delivery group. However, the effect on daily life decreased. These findings are inconsistent with the previous studies.9,10 Furthermore, we found that the prevalence of any UI and of SUI tended to decrease in the cesarean delivery group during the first 3 months postpartum but did not change in the vaginal delivery group during that period. However, decreases in moderate or severe UI and in daily life interference during the first 3 months were observed in the vaginal delivery group.
Our findings give health professionals a better understanding of postpartum UI and will help with maternal decision-making to select the most appropriate childbirth method and intervention strategy.
The main strength of our study was its longitudinal design that included multiple time points over the course of 1 year. Thus, the association between the two delivery methods and UI at each time point over 1 year was identified. In addition, the change in UI across the first year postpartum was identified by repeated-measures statistical testing using a within-subject comparison design. Finally, all UI indices in this study were assessed with a valid and reliable instrument, which was confirmed by objective measures.25–27
The limitations of this study should be considered. The factors that may influence the increasing trend of UI across the first year postpartum were not studied. Subgroup analysis for postpartum UI such as assisted vaginal delivery, previous route of delivery, or cesarean delivery after a period of labor was not performed. The prevalence of UI in prepregnancy was not assessed in this study; such information in future investigations will allow estimation of the effect of pregnancy as well as route of delivery. Additionally, other health indicators of women who underwent vaginal and cesarean deliveries such as sexual functioning, pain, and physical and mental health were not assessed. The subjective experience of women after vaginal or cesarean delivery could also be explored using an interpretive method.
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