Urinary incontinence (UI)1 and anal incontinence2 are functional pelvic floor disorders that increase with age3 but present in young people. They are major health problems affecting quality of life and psychological (loss of self esteem, depression) as well as social (reclusion, isolation) areas of the affected persons.4
Prospective data assessing the severity of UI and anal incontinence during pregnancy, persistency of incontinence after delivery, or its relationship with the level of impact on daily life are scarce.5–6 Distinguishing time of onset, severity, and persistence of both incontinences during and after pregnancy may provide an insight into the natural history of incontinence, and hence in the differences between transient incontinence due to the hormonal and mechanical effects of pregnancy and the damage that may occur as a result of delivery.
Incontinence during pregnancy has been linked to age,7 body mass index (BMI),8 strenuous physical exercise,9 or smoking history.8 Vaginal birth is a major determinant of incontinences. Instrumental deliveries (forceps and vacuum) can increase risk10–11 especially in combination with episiotomy;12 however, certain inconsistencies in the univariable analysis of these practices and related complications (such as grade III and IV tears) have been found, suggesting that they operate as markers of the existence of a vaginal delivery.13–14 All these data are not conclusive due mainly to variations in the study designs, sample sizes, or the length of time in the postpartum period chosen for evaluation of incontinence (ranging from weeks to months). These differences are even more pronounced in anal incontinence studies.
We aim to estimate the frequency and severity and to identify risk factors of UI and anal incontinence during pregnancy and postpartum in previously continent nulliparous women.
MATERIALS AND METHODS
We designed a cohort study approved by the Catalan Agency for Health Technology Assessment and Research institutional review board of healthy, continent, nulliparous, pregnant women attending the public health care system of Catalonia. In 2008, there was a total of 87,567 births (70.1% in public maternities); 18,992 (21.7%) of them occurred in nulliparous women.
Consecutive candidate women with symptoms of UI and anal incontinence before pregnancy (reported by themselves) or presence of neurological diseases, cognitive disorders, urological pathology (noninfectious), history of abortion, impaired mobility, previous urogynecologic surgery, or current treatment with drugs (benzodiazepines, diuretics), as well as difficulty in reading and/or understanding Spanish language were excluded. All participants were informed of the nature and objectives of the study and signed informed consent freely, which did not preclude withdrawal from the study at any time during follow-up. The identity of pregnant women and participating centers was strictly protected.
To estimate the sample size, a 3% α error under the assumption of maximum uncertainty (assuming maximum variance), and a 20% of replacements to compensate for eventual losses were accepted; so it was considered that 1,279 pregnant women should be included.
Participants were included in the cohort at the first visit of their pregnancy; recruitment took place between June 2007 and June 2008, and monitoring finished on January 2009. Health care staff collected sociodemographic data and the changes associated with pregnancy during control visits and obstetric and fetal characteristics at the time of birth (from delivery records).
Participants completed a self-administered questionnaire in each of the trimesters and in the postpartum visit (average of 7 weeks). For the assessment of UI, two adapted and validated into Spanish questionnaires, the Incontinence Severity Index15 and the short version of the International Consultation on Incontinence Questionnaire16 were used, while for anal incontinence the Jorge and Wexner Faecal Continence Grading Scale17 was administered. Urinary incontinent women were defined as those who responded affirmatively to at least some of the questions of the Incontinence Severity Index on frequency or amount, similarly anal incontinent women were those who responded affirmatively to the question on uncontrolled passage of flatus or stool. Incontinence severity was classified as slight, moderate, severe and very severe18 and the International Consultation on Incontinence Questionnaire allowed the classification into stress, urge, or mixed UI.1 The persistence of incontinence was defined as leakage in the third trimester still unresolved in the postpartum period. Participants with a nonresponse in any of the monitoring times were not considered in the estimation of rates.
Weight gain was categorized in terms of baseline body mass index (BMI), thus a gain of 18.5 kg or more, 10 kg or more, 9 kg or more, and 6 kg or more was considered excessive in participants with low BMI, normal BMI, overweight, and obesity, respectively.19
Prevalence, cumulative incidence, and incidence density rates were calculated in each of the three trimesters of pregnancy and in the postpartum visit. The time, in weeks of gestation, until the first report of incontinence was also estimated, and the likelihood of remaining continent was calculated by survival analysis techniques (Kaplan-Meier). The correlation between the severity of UI and the level of interference in daily living was assessed (Spearman). The losses to follow-up were studied during pregnancy and the postpartum period and compared (χ2 test) with those who remained in the study according to the presence and type and severity of UI, presence of anal incontinence, and sociodemographic and anthropometric characteristics.
The association between outcome variables and the other variables studied as well as the assessment of persistence of incontinence was measured by means of a univariable analysis. To assess the association of potential risk factors, hazard ratios (HRs) were estimated by Cox regression for all participants and stratified by presence of incontinence in pregnancy (continent/incontinent) and postpartum. The independent effect of each variable was assessed by a multivariable analysis. For the analysis of delivery risk factors only singleton pregnancies were included (eight twin pregnancies were excluded).
The level of statistical significance was set at P≤.05.
A total of 1,128 continent pregnant nulliparous women (88.2% of the estimated sample size) were included. There were no statistically significant differences between participants who remained in the study and those who dropped out because of fetal losses (n=76) or in the postpartum period (n=30), in terms of either the incontinence-related variables or the anthropometric ones. Differences were found only for the variables place of birth and educational level among those cases lost to follow-up during pregnancy. The description of baseline characteristics of the study population is presented in Table 1.
The incidence of UI at some time during pregnancy was 39.1% (95% CI 36.3-41.9). Table 2 shows the evolution of UI frequency measures. Participants mainly presented stress UI, with figures exceeding 50%, in each of the moments of data collection; urge UI reached 30% in the postpartum period (Table 3). Figure 1 shows the evolution of severity by data collection time, as well as the changes in trends between slight and moderate UI, with a tendency for slight to become moderate UI. The correlation between severity of UI and level of interference in daily living was moderate but statistically significant in all periods of data collection with correlation coefficients of 0.35, 0.13, 0.46, and 0.47 for the first, second, and third trimesters and postpartum, respectively.
Figure 2A identifies the frequency, severity and impact on daily life of UI by time of onset of the following groups: participants who never leaked (group A), who leaked after pregnancy only (group B), who leaked during pregnancy but resolved (group C), and with leakage unresolved at the end of the study (group D). The proportions of women aged more than 35 years (16.0% compared with 6.1%, P=.087) and overweight/obese at baseline (33.0% compared with 17.4%, P=.050) were higher in group D than in group B. There were no differences in the level of severity.
Survival analysis explained that 20% of pregnant women presented or had presented with UI at 26 weeks of gestation, and this proportion reached 40% at 36 weeks of gestation. Finally, 56% of pregnant women remained continent at the end of pregnancy.
Ten percent of women presented anal incontinence at some point during pregnancy (95% CI 8.3-12.3). The evolution of the anal incontinence frequency is depicted in Table 4. The presence of anal incontinence was mainly characterized by loss of flatus in more than 90% of cases and common in all periods. In the postpartum period, loss of liquid or solid stool increased affecting slightly over 30% of participants (Table 5).
Figure 2B summarizes the frequency of anal incontinence by time at onset (during gestation and postpartum); the distributions of age and BMI at baseline were not statistically different in groups B and D.
Survival analysis techniques estimated that 5% of pregnant women presented or had presented with anal incontinence at 25.4 weeks of gestation, while 10% did so at 34.2 weeks of gestation. At the end of pregnancy, 86% of women remained continent.
The risk of UI increases in pregnant women aged more than 35 years, in women who are overweight or obese at baseline, and in those with a family history of UI, while the risk of anal incontinence rises with age and excessive weight gain during pregnancy (Table 6).
Risk factors identified for the occurrence of both incontinences in the postpartum period are having been incontinent during pregnancy and vaginal delivery. The results of univariable analysis showed no differences between eutocic and dystocic deliveries; regarding cesarean deliveries, unlabored cesarean deliveries tended to be more protective that labored ones, although without reaching statistical significance. Their inclusion in the multivariable analysis did not improve the final model. The association of vaginal delivery with UI is statistically significant in both women who were continent during pregnancy and those who were incontinent, although with a somewhat larger effect for the former (Table 7). However, vaginal delivery was significantly associated with anal incontinence only in those women who were incontinent during pregnancy (Table 8). As five (2.6%) grade III tears and no grade IV tears were reported, this variable could not be analyzed despite its evident importance.
Of the 322 pregnant women with UI during the third trimester, 85 (26.4%) persisted in the postpartum period, whereas this only happened for 19 (29.7%) of 64 women with anal incontinence during pregnancy. At an average of 7-week postpartum follow-up, vaginal delivery is a risk factor for the persistence of UI (HR 2.1, 95% CI 1.1-4.3) and anal incontinence (HR 4.8, 95% CI 1.1-21.4).
The attributable risk, that is, the proportion of incontinence incidence among women who delivered vaginally that would be preventable by cesarean deliveries is 67.8% (95% CI 50.2-85.4%) for UI and 58.3% (95% CI 26.3-90.3%) for anal incontinence. The population attributable risk is 49.1% (95% CI 36.3-61.8%) and 42.2% (95% CI 19.0-65.4%) for UI and anal incontinence, respectively.
This study aimed to look at the patterns, by distinguishing time courses and severity, of UI and anal incontinence onset and was able to corroborate some of the major risk factors for incontinence during pregnancy and early postpartum. The ideal model for studying the natural history of incontinence in pregnancy is through continent, healthy (more than 93% did not report any complaints), nulliparous women because the pelvic floor remains intact.
This study has brought to light the high incidence of UI and anal incontinence over the three trimesters of pregnancy, particularly the second. The incidence rate of UI estimated in pregnancy (39.1%) is similar to the figure of 45% calculated in a prospective study20 but differs in the postpartum for women who remained continent during pregnancy (9% compared with 21%).6 Possible explanations could be variations in the evaluation questionnaire, differences in the cesarean delivery rate (higher in the current study), or differences in the inclusion/exclusion criteria. A recent research article21 reports 17.1% urine leakage 3-6 months after first delivery among women continent before their pregnancy; however, the continence status during pregnancy is not stated. More relevant are the observed rates of anal incontinence incidence, mainly of flatus. Prevalence rates of both incontinences are similar to those of other studies.22–23 The leakage of small amounts (mainly drops) could be a reason why pregnant women downplay this problem,24 even considering it as simply an aspect of their own condition. In fact, we cannot find any difference in the level of severity between women who leaked after pregnancy only and those with leakage unresolved at the end of the study; nevertheless, our data have shown a positive correlation, albeit modest, between severity and the impact on daily living.
Age, family history, baseline BMI, and excess weight gain during pregnancy are associated with a higher risk of incontinence. These results resemble those found in other studies7,8,25 suggesting that intrinsic factors may favor the occurrence of incontinences throughout gestation and increase the risk after delivery.
The present study supports that the occurrence of UI and anal incontinence during pregnancy is related to the presence of incontinence in the postpartum period, and vaginal delivery increases the risk of persistent incontinence. The findings are consistent with those of a previous prospective study6 and reinforce once again the importance of mode of delivery for postpartum incontinence as well as its independence of the presence or absence of incontinence during pregnancy. Associations with other obstetric factors were not statistically significant, as in other studies.21 There are no differences between eutocic and instrumented deliveries and among different types of cesarean deliveries, as reported elsewhere.26 As for episiotomy, the significant association found in the univariable analysis disappeared in the multivariable model, something also observed in other studies and which leads to the conclusion that episiotomy acts as an indicator of vaginal delivery.6,14
The estimated population attributable risk associated with vaginal delivery shows that about half of the cases of incontinence in primiparous women would be prevented if they had had a cesarean delivery. However, this figure does not imply the use of cesarean delivery as a preventive strategy to reduce incontinence, as has been discussed in other reports.27 Moreover, maternal and neonatal morbidity associated with cesarean delivery surpasses that of vaginal delivery and should be taken into account when balancing risks and benefits.28 Finally, development of incontinence may be attributable to factors beyond vaginal compared with cesarean deliveries.
Certain limitations of the study could be related to the design. Losses to follow-up and nonresponses are important in longitudinal studies; nevertheless, lost cases were not significantly different in presence of incontinence. A second limitation could be the lack of representativeness of the study population. Catalonia has a public system with universal coverage and free access to health care for all citizens, which coexists with a private health insurance system; mode of delivery, for instance, is different in the two systems (the proportion of cesarean deliveries is 22.5% in public hospitals and 40.9% in private ones). Extrapolating the results of this study can only be done to pregnant women attending the public health care system and with sociodemographic and anthropometric characteristics similar to those described. With regard to postpartum incontinence, the short period for assessment (average of 7 weeks) limits the analysis and the comparison with longer follow-up studies. However, the rate of incontinence at 2-3 months after delivery did not change significantly over the 6- to 12-month postpartum period.29–30 We consider that information about incontinence symptoms at 6-8 weeks after delivery is a clue to implement preventive strategies postpartum; most women are attended at the end of puerperium, and adding questions about UI and anal incontinence in the postpartum check-ups, by means of validated questionnaires, should be easy for the clinicians.
In conclusion, this systematic, prospective design provides in our setting valid incidence rates of UI and anal incontinence with accurate confidence intervals and identifies various risk factors for incontinence during both pregnancy and the postpartum period. These data corroborate that gestation and childbirth increase the frequency of UI and anal incontinence, which in consequence emerge as a common health problem, despite usually being hidden or not considered important, with a degree of severity that effects the daily lives of pregnant and puerperal women. Finally, we identified risk factors relate to lifestyle and obstetric practices, which are either amenable to modification or useful to recognize pregnant women at higher risk of incontinence.
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