Urogynaecology. Introduction. M Gyhagen, a M Bullarbo, a,b TF Nielsen, a,b I Milsom a

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1 DOI: / Urogynaecology A comparison of the long-term consequences of vaginal delivery versus caesarean section on the prevalence, severity and bothersomeness of urinary incontinence subtypes: a national cohort study in primiparous women M Gyhagen, a M Bullarbo, a,b TF Nielsen, a,b I Milsom a a Department of Obstetrics and Gynaecology, Sahlgrenska Academy at Gothenburg University, Gothenburg, Sweden b Department of Obstetrics and Gynaecology, S odra Alvsborgs Hospital, Boras, Sweden Correspondence: Dr M Gyhagen, Department of Obstetrics and Gynaecology, Sahlgrenska University Hospital, SE Gothenburg, Sweden. maria.gyhagen@vgregion.se Accepted 7 May Published Online 21 June Objective To study the effect of one vaginal delivery (VD) compared with one caesarean section (CS) on the prevalence, severity and bothersomeness of urinary incontinence (UI) subtypes stress (SUI), urge (UUI) and mixed (MUI) 20 years after delivery. Design Registry-based national cohort study. Setting Women who returned postal questionnaires (response rate 65.2%) in Population Primiparae with one birth in (n = 5236) and no further births. Methods Medical Birth Register data were linked to a questionnaire. Analysis of variance and multivariate analysis were used to obtain adjusted prevalences and odds ratios (adjor). Main outcome measures Prevalence, risk factors, severity, bothersomeness of UI subtypes. Results The prevalence of SUI, UUI and MUI was 15.3, 6.1, 14.4%, respectively, and was higher for all subtypes after VD versus CS. Moderate to severe incontinence was more prevalent after VD (21.3%) compared with CS (13.5%; adjor 1.68, 95% confidence interval [95% CI] ). Bothersome incontinence differed between MUI (38.9%), UUI (27.1%) and SUI (18.0%). The prevalence of bothersome UI was higher after VD compared with CS (11.2 versus 6.3%; adjor 1.85, 95% CI ) and consulting a doctor for UI was reported more often after VD than CS. Bothersome MUI occurred in 40.0% of incontinent women after VD compared with 29.9% after CS (adjor 1.65, 95% CI ). Symptomatic pelvic organ prolapse was an important modifier of UI with regard to its prevalence, duration, type and bothersomeness. Conclusion The prevalence of SUI, UUI and MUI was higher and moderate to severe UI and bothersome UI were reported more often after VD than CS 20 years after one delivery. Keywords Bothersomeness, caesarean section, epidemiology, mixed urinary incontinence, severity, stress urinary incontinence, urge urinary incontinence, vaginal delivery. Please cite this paper as: Gyhagen M, Bullarbo M, Nielsen TF, Milsom I. A comparison of the long-term consequences of vaginal delivery versus caesarean section on the prevalence, severity and bothersomeness of urinary incontinence subtypes: a national cohort study in primiparous women. BJOG 2013;120: Introduction Urinary incontinence (UI) is a global, highly prevalent, and costly condition that affects women of all ages, and its impact on quality of life is known to be substantial. 1,2 The high prevalence of UI obtained from epidemiological surveys has necessitated the development of a system to grade its severity in order to determine the clinical relevance of the problem and to select women for further evaluation and treatment. 3,4 The severity of UI has been shown to be associated with the subjective appreciation of the condition, indicating an increase in bother with increasing severity of UI. 5 Subtypes of UI (stress urinary incontinence, SUI; urge urinary incontinence, UUI; and mixed urinary inconti ª 2013 RCOG

2 Urinary incontinence subtypes 20 years after one childbirth nence, MUI) have been shown to be associated with different degrees of severity and bothersomeness. 5,6 It is therefore necessary to consider UI subtypes when analysing the late consequences of vaginal birth in comparison with caesarean section (CS), which is the subject of this study. To date there is some information about the prevalence and distribution of subtypes of UI after vaginal delivery (VD). Stress urinary incontinence (SUI) has almost consistently been shown to be associated with VD, but information about UUI and MUI is either lacking or inconclusive. 7 The aim of the present study was to investigate the influence of VD compared with CS on the prevalence, severity and bothersomeness of UI subtypes (SUI, UUI and MUI) 20 years after one birth. Methods A national survey of pelvic floor dysfunction, the SWEdish Pregnancy, Obesity and Pelvic floor (SWEPOP) study was conducted in 2008 assessing pelvic floor function in women 20 years after one single pregnancy terminating either in a VD or a CS. Women who participated in this study were obtained from the Medical Birth Registry, at the Epidemiology Centre of the National Board of Health and Welfare in Sweden. Inclusion criteria for participation in this study were primiparae with one single birth and no further births. Exclusion criteria were multiparity and multifetal or ongoing pregnancy. Women with a body mass index (BMI) <25 kg/m 2 at delivery and women who had given birth to a child of <4000 g were chosen at random from the total population who had one single birth between 1985 and 1988 and no further births. All women with a BMI 25 kg/m 2 and women who had given birth to a child weighing 4000 g or had a recorded elective CS during the same calendar period were included to obtain sufficient numbers of these groups. Women were included regardless of maternal health status, and maternal and fetal complications for a greater generalisation of results and therefore a more realistic basis for consultation. A total of women who fulfilled these criteria were obtained from the Medical Birth Registry and addresses for 9423 of these women could be traced in the Swedish population address register, which includes all persons who are registered as resident in Sweden. The missing 694 women included newly deceased women or women with unknown address or hidden personal identity. A letter was sent to the 9423 women who were asked to provide written, informed consent to participate and to complete an enclosed questionnaire regarding current pelvic floor function. After three mailing cycles during a 4-month period the questionnaire was returned by 6148 women. Of the 6148 that returned questionnaires 6060 women were able to participate or gave their informed consent for participation in the study. A further 824 women were excluded from the study because they affirmed multiparity, or multifetal or ongoing pregnancy in the questionnaire. In this study the following numbers of women were excluded: 716 due to multiparity; 43 due to multifetal pregnancy; six due to ongoing pregnancy and 59 due to missing data about parity in the questionnaire. In all, 5236 women constituted the final study population but a further 118 had missing data for important factors such as mode of delivery so the final number was A detailed description of the study population and methods, including an analysis of the nonresponders, has been described in detail previously. 8 Ethical approval was obtained from the Regional and National Ethics Review Boards (the Ethics Committee at Sahlgrenska Academy, Gothenburg University, and the National Board of Health and Welfare). The results of this study have been reported according to the STROBE statement. The questionnaire included 31 questions about current height and weight, urinary or anal incontinence and symptomatic pelvic organ prolapse (spop), menstrual status, hysterectomy, the menopause and hormone treatment. Urinary incontinence was defined according to the International Continence Society 9 and by the question Do you have involuntary loss of urine? Participants reporting UI were classified as having SUI if there was involuntary loss of urine in connection with coughing, sneezing, laughing, or lifting heavy items; UUI was present if loss of urine was in connection with a sudden and strong urge to void; and MUI if both components were present. The severity of UI was assessed using the Sandvik severity index 3 and values were created by multiplying the reported frequency (four levels) by the amount of leakage (two levels). The resulting index value (1 8) was further categorised into slight (1 2), moderate (3 4) and severe (6 8). 3 The severity index has been validated against a 48-hour pad-weighing test. 10 According to this test, slight incontinence means a leakage of 6 g/24 hours (95% confidence interval [95% CI] 2 9), moderate incontinence means 17 g/24 hours (95% CI, 13 22) and severe incontinence describes 56 g/24 hours (95% CI, 44 67). The severity index is therefore a semi-objective and quantitative measure and does not include the woman s subjective perception of her leakage as being a problem or not. A question about the impact of incontinence was also included. The impact of incontinence in terms of bothersomeness was dichotomised into a minor problem (no problem/a small nuisance) and bothersome (some bother/much bother/a major problem). Significant incontinence, a term that has been used earlier in the EP- INCONT study 11 was defined as the combination of bothersome and moderate to severe incontinence according to the Sandvik severity index. 3 ª 2013 RCOG 1549

3 Gyhagen et al. Statistical methods Statistical analysis was performed with SAS 9.1 (SAS Institute Inc., Cary, NC, USA). For cohort characteristics chi-square test was used to compare categorical variables and the Student s t-test for continuous variables. A P-value <0.05 was considered statistically significant. Adjusted prevalences were calculated using an analysis of variance after taking other risk factors into account. Odds ratios (ORs) and their 95% confidence intervals were calculated from the logistic regression model. A logistic regression model was used to assess risk factors for bothersome UI. Potential risk factors used in the analysis for bothersome UI were mode of delivery, infant birthweight dichotomised <4500 or 4500 g, maternal age, current BMI (kg/m 2 ), spop and UI >10 years. For bothersome SUI, UUI and MUI a backward logistic regression analysis was made including maternal age, mode of delivery, current BMI, spop, UI >10 years, and infant birthweight 4500 g. Odds ratios and their 95% confidence intervals were calculated from the model. A linear regression was used to assess severity of UI. Potential risk factors used in the analysis were mode of delivery, age at delivery, current BMI, infant birthweight and subtypes of UI, spop and UI >10 years. The prevalence data permitted the calculation of the number of CS needed to avoid one case of UI using the number-needed-to-treat principle. The number needed to treat was calculated as the inverse of the absolute risk reduction, where risk reduction was the difference of adjusted prevalence of UI between VD and CS. Results The questionnaire was returned by 65.2% (n = 6148). The basic characteristics of these women have been described in detail previously. 8 In the total cohort (n = 5118) SUI occurred in 15.3%, UUI in 6.1% and MUI in 14.4%. Prevalences in the total population were higher after VD compared with CS and the increase was 4.4% for SUI, 2.8% for UUI and 4.7% for MUI (Table 1). However, in incontinent women the percentage of each subtype was very similar after both modes of delivery. In incontinent women (n = 1899) moderate to severe incontinence (score 3 8, according to the Sandvik severity index) occurred in 68.1% of women with MUI, in 53.7% with UUI and 40.9% of women with SUI (Table 2). Among incontinent women the percentage of moderate to severe UI was 52% (181/348) after CS and 54% (831/1551) after VD. In contrast, the prevalence of moderate to severe incontinence was higher for each subtype of incontinence after VD compared with CS and the difference in prevalence of moderate to severe UI between VD and CS was 7.8% (OR 1.68; 95% CI ) (Table 3). The percentage of severe UI was 19% (CS 67/348; VD 300/1551) after both modes of delivery. The number-needed-to-treat to avoid one case of moderate to severe UI was 13 CS. Bothersome incontinence was reported by 27.2% (532/ 1954) of all incontinent women (Table 4). The prevalence of bothersome UI was significantly higher after VD compared with CS (11.2% versus 6.3%, OR 1.85; 95% CI ) (Table 1). The number-needed-to-treat to avoid one Table 1. The prevalence of urinary incontinence subtypes and different measures of impact of incontinence grouped according to mode of delivery Crude Adjusted* VD CS OR (95% CI) VD CS OR (95% CI) SUI 16.3% 642/3931 UUI 6.4% 252/3931 MUI 15.3% 601/3931 Bothersome UI 11.2% 449/3995 Significant UI 9.7% 386/3995 Sought doctor 5.2% 207/ % 141/ % 58/ % 138/ % 83/ % 76/ % 44/ ( ) 16.4% 12.0% 1.42 ( ) 1.33 ( ) 6.8% 4.0% 1.66 ( ) 1.37 ( ) 15.4% 10.7% 1.46 ( ) 1.71 ( ) 11.2% 6.3% 1.85 ( ) 1.59 ( ) 9.7% 5.7% 1.76 ( ) 1.44 ( ) 5.4% 3.2% 1.65 ( ) *Adjusted for maternal age, current BMI and infant birthweight ª 2013 RCOG

4 Urinary incontinence subtypes 20 years after one childbirth Table 2. Severity of urinary incontinence in each subtype of urinary incontinence grouped according to the Sandvik severity index Mild % 3 4 Moderate % 6 8 Severe % 3 8 Moderate and severe % All (n = 1899) (n = 887) (n = 645) (n = 367) (n = 1012) SUI UUI MUI Vaginal delivery (n = 1551) (n = 720) (n = 531) (n = 300) (n = 831) SUI UUI MUI Caesarean section (n = 348) (n = 167) (n = 114) (n = 67) (n = 181) SUI UUI MUI case of bothersome UI was 20 CS. In incontinent women the prevalence of bothersome UI was 5.4% higher after VD compared with CS (OR 1.35; 95% CI ) (Table 4). There were significant differences (Table 4) in the percentage distribution of women reporting bother between the different subtypes of incontinence (38.9% for MUI, 27.1% for UUI and 18.0% for SUI). Bothersomeness occurred significantly more often in vaginally delivered women having MUI compared with women delivered by CS having MUI. The difference was 10.1% (OR 1.65; 95% CI ). However, the difference between VD and CS in bothersomeness was not significant for SUI and UUI (Table 4). Significant UI was reported by 8.9% (462/5199) of all women in this study. The prevalence of significant UI was 9.7% after VD compared with 5.7% after CS (OR 1.76; 95% CI ) (Table 1). To avoid one case of significant UI one has to perform 25 CS. The logistic regression analysis of risk factors for bothersome UI showed that the type of UI, infant birthweight, current BMI, the presence of spop and a duration of UI >10 years were significant risk factors for UI. Logistic regression analysis of risk factors for bothersome UI showed that spop was a significant risk factor for all three subtypes of UI; that duration of UI was a risk factor for UUI and MUI but not for SUI; and that current BMI was a significant risk factor for MUI only (Table 5). In order of importance, linear regression analysis showed that any UUI, duration of UI >10 years, spop and BMI were significant (P < ) risk factors for the severity of incontinence. Maternal age was not, however, an independent risk factor of either severity or bothersomeness of UI. In a subgroup analysis of incontinent women with and without spop it was found that spop was associated with the symptom of UUI, and hence MUI, but spop did not change the prevalence of the symptom of any SUI (isolated or in combination with MUI) (Table 6). Among incontinent women, 13.2% (251/1899) had consulted a doctor and the prevalence of seeking a doctor for incontinence was significantly higher after VD compared with CS (Table 1). The prevalence of any treatment for UI was 2.7% (108/3985) after VD and 1.8% (22/1202) after CS. The difference was not significant (OR 1.49; 95% CI ), which may be due to a lack of power. Discussion Main findings To our knowledge, this study is the first to compare VD and CS with respect to the prevalence of the three main subtypes of incontinence remote from birth (i.e. 20 years after delivery). The study has shown that the prevalence of all three subtypes of UI was higher after VD compared with CS. This was also the case for the prevalence of bothersome UI, the severity of UI and the severity of each subtype of UI. Moderate to severe incontinence occurred in two-thirds of women with MUI, in every second woman with UUI, whereas two-thirds of women with SUI had mild symptoms. Multivariate regression analysis showed that any UUI, duration of UI, spop and BMI were risk factors for severity of UI and for bothersome UI. These findings were supported by the fact that women 20 years after a VD significantly more often consulted a doctor for UI complaints. spop was found to be an important modifier of UI with regard to its prevalence, duration, type and degree of bother. Strengths and weaknesses The strengths and weaknesses of the SWEPOP study have been discussed previously. 8,12 It should be noted that for ª 2013 RCOG 1551

5 Gyhagen et al. Table 3. The severity of incontinence assessed according to the Sandvik severity index 3 in women with urinary incontinence and the subtypes of incontinence grouped according to mode of delivery (n = 5118) Crude Adjusted* VD % CS % OR (95% CI) VD % CS % OR (95% CI) All UI (n = 1899/5118) 1 2 mild ( ) ( ) 3 4 moderate ( ) ( ) 5 8 severe ( ) ( ) 3 8 moderate to severe ( ) ( ) SUI (n = 783/5118) 1 2 mild ( ) ( ) 3 4 moderate ( ) ( ) 5 8 severe ( ) ( ) 3 8 moderate to severe ( ) ( ) UUI (n = 310/5118) 1 2 mild ( ) ( ) 3 4 moderate ( ) ( ) 5 8 severe ( ) ( ) 3 8 moderate to severe ( ) ( ) MUI (n = 739/5118) 1 2 mild ( ) ( ) 3 4 moderate ( ) ( ) 5 8 severe ( ) ( ) 3 8 moderate to severe ( ) ( ) *Adjusted for maternal age, current BMI, and infant birthweight. the purposes of this report validated instruments assessing the severity 3,10 and bothersomeness 11 of UI were used and there was also an assessment of the rate of medical consultation. Some limitations of the present investigation must be considered. First, women with incontinence may be more predisposed to participate in studies and therefore UI might be overestimated. Second, the symptoms of UI were selfreported. However, several studies have shown that selfreported symptoms are consistent and valid when assessing current UI and changes in incontinence severity over time, which applies to our study. This study also lacks information on whether UI was present or not before or/and during pregnancy or started after delivery. However, there is little evidence to suggest any difference in UI prevalence before the first pregnancy or during pregnancy in women grouped according to mode of delivery. It was not possible to assess the importance of the length of the second stage of delivery, as this is unfortunately not documented in the Medical Birth Registry. Interpretation of our results in relation to other studies The prevalence of UI and all three subtypes of UI was higher after VD compared with CS, which raises the question of causality. However, it should be noted that a causal link between vaginal birth/trauma and UI cannot be shown by a statistical association alone and must be supported by pathophysiological knowledge from other fields of investigation. There are, however, studies using magnetic resonance imaging, ultrasound and neurophysiological techniques that have been published supporting a causal relationship between VD and pelvic floor damage, which have been summarised in a review regarding the pathophysiology of UI. 13 Determination of subtypes of UI from a questionnaire has been recommended to be included in epidemiological studies on UI 1,14 because they are associated with different degrees of severity and bothersomeness. 5,11 This was confirmed by the present study where we found that SUI, UUI and MUI, in that order, were associated with increasing severity and bother of UI. The subjective perception of the condition, if it causes bother or not, and to what degree, could be considered to be the crucial criteria as to whether the symptoms are sufficiently relevant to motivate the women to seek medical attention and treatment. 1 The concept significant urinary incontinence is one way to increase the discriminatory power by considering women with moderate to severe UI only (as defined by the Sandvik severity index), and who at the same time state that their symptoms are bothersome. According to Hannestad 1552 ª 2013 RCOG

6 Urinary incontinence subtypes 20 years after one childbirth Table 4. Percentage number of women reporting bothersome urinary incontinence grouped according to subtype and mode of delivery Bother Odds increase of bother Bother Crude Bother adjusted* % OR (95% CI) VD % CS % OR (95% CI) VD % CS % OR (95% CI) All UI n = 1954 SUI n = 782 UUI n = 310 MUI n = ( ) ( ) (ref.) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) *Adjusted for maternal age, current BMI and infant birthweight. Table 5. Logistic regression analysis of risk factors for bothersome UI and subtypes of UI UI (n = 1864) SUI (n = 768) UUI (n = 307) MUI (n = 712) OR (95% CI) OR (95% CI) OR (95% CI) OR (95% CI) Maternal age 1.00 ( ) UI type* 1.63 ( ) Infant birthweight 4500 g** 1.87 ( ) 1.97 ( ) 1.59 ( ) 2.04 ( ) Current BMI (kg/m 2 ) 1.04 ( ) 1.01 ( ) 1.03 ( ) 1.06 ( ) spop*** 1.73 ( ) 1.72 ( ) 2.09 ( ) 1.69 ( ) UI >10 years**** 1.87 ( ) 1.47 ( ) 2.44 ( ) 2.18 ( ) VD versus CS 1.18 ( ) References: Categorical variables. *SUI. **IBW <4500 g. ***spop no. ****UI 10 years. Table 6. Crude and adjusted prevalence and ORs of urinary incontinence subtypes in women with symptomatic pelvic organ prolapse compared with women without spop spop yes and UI yes n = 383 spop no and UI yes n = 1495 spop yes and UI yes spop no and UI yes % % Crude OR (95% CI) % % Adjusted* OR (95% CI) SUI n = 776 UUI n = 306 MUI n = 733 Any SUI n = 1522 Any UUI n = n = n = n = n = n = n = ( ) ( ) 1.10 ( ) ( ) 1.84 ( ) ( ) ( ) ( ) ( ) ( ) *Adjusted for maternal age, current BMI and infant birthweight. ª 2013 RCOG 1553

7 Gyhagen et al. et al., 11 all women with significant UI should be regarded as potential patients and in need of treatment. The prevalence of subtypes of UI is age-dependent. 1 A large population-based prevalence study of UI subtypes in women in four European countries showed that in the age band years the distribution of SUI, UUI and MUI was 41, 16 and 36% (others 7%), respectively. 15 The corresponding distribution for the total cohort of incontinent women in the present study (mean age 51 years) was very similar (43, 17 and 40%), and seems therefore to be representative for middle-aged European women. Reduction of the prevalence and odds of SUI after CS compared with VD has previously been reported. 7,16 19 Data on UUI and MUI are, however, conflicting. 7,16,20 Most cross-sectional and cohort studies with short or 1-year and longer follow-up could not demonstrate a significant difference in the prevalence of UUI and MUI between the two modes of delivery. 7 A possible explanation for this difference between studies may be lack of statistical power, because the number of women who gave birth by CS in the cohort studies with 1-year and longer follow-up was low. 18,19,21 In the EPINCONT cross-sectional study 16 the difference in prevalence between VD and CS was significant for SUI, but not for UUI and MUI. The absence of a difference for UUI and MUI may be attributed to heterogeneity of parity (1 4), a large proportion of younger women (55% <40 years) in whom UUI and MUI is less common, and the relatively small fraction (6%) of CS in that study. In an analysis with SUI as reference, bothersomeness was higher for UUI and MUI compared with SUI and the odds increase was greatest for MUI (269%). The analysis of risk factors for bothersome UI subtypes showed that MUI was associated with three risk factors (UI >10 years; spop; BMI); UUI with two risk factors (UI >10 years; spop); and SUI with only one risk factor (spop). That spop is a risk factor for all three subtypes of bothersome UI may explain the strong association between spop and UI and the high prevalence of UI in women with spop (62%) shown in an earlier SWEPOP study. 12 A subgroup analysis of all women with UI in this study further showed that a majority of women with prolapse had mixed UI whereas those without prolapse had predominantly isolated SUI, indicating an independent effect of symptomatic genital prolapse on the distribution of UI subtypes. Conclusions The prevalence of all three subtypes of UI was higher after VD compared with CS. This was also the case for the severity and bother caused by UI and by each subtype of UI. The study also demonstrated that SUI, UUI and MUI, in that order, are associated with increasing severity and bother of UI. Any UUI, duration of UI, spop and BMI were risk factors for severity of UI and for bothersome UI. These findings indicate a long-term harmful effect on the pelvic floor from VD both from an objective and subjective perspective. The results of this study also indicate that spop may be both an indicator of the aggregate tissue trauma at VD and an important modifier of UI with regard to its prevalence, duration, type and degree of bother. Since prevention is superior to treatment we suggest that these results should be an incitement to improve counselling about risks associated with mode of delivery. Further it calls for measures to optimise the conduct of labour and to improve the identification of women at risk for late pelvic floor damage. Finally, it is important to inform women about the predictable, preventable and reversible effect on urinary continence of overweight and obesity, a precaution and measure that may be most urgent after VD. Disclosure of interests We declare that we have no conflict of interests. Contribution to authorship All authors were involved in the conception and design of the study, acquisition of data and interpretation of the results as well as the writing of the manuscript. All authors approved the final version of the submitted manuscript. MG and IM take full responsibility for the integrity of the data and the accuracy of the data analysis. Details of ethics approval Ethics approval for the SWEPOP study was obtained from the Regional and the National Ethics Review Boards (the Ethics Committee at Sahlgrenska Academy, Gothenburg University, ref no , 13 August 2007 and the National Board of Health and Welfare, ref no /2007, 26 October 2007). Funding The study was supported by a National LUA/ALF grant no and the Region of V astra G otaland, grants from The G oteborg Medical Society and Hjalmar Svenssons Fund, The funding source had no role in the study design, data analysis, data interpretation or writing of the report. MG and IM had full access to all study data and had final responsibility for the decision to submit for publication. Acknowledgements We thank Ms Marianne Sahlen and Ms Anja Andersson for help with data registration and Bj orn Areskoug MSc for expertise in statistical programming. & References 1 Milsom I, Altman D, Herbison P, Lapitan MC, Nelson R, Sillen U, et al. Epidemiology of urinary (UI) and faecal (FI) incontinence and 1554 ª 2013 RCOG

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