Effects of Carrying a Pregnancy and of Method of Delivery on Urinary Incontinence

Abstract & Research article

Background
This study was carried out to identify risk factors associated with urinary incontinence in women three months after giving birth.

Methods
Urinary incontinence before and during pregnancy was assessed at study enrolment early in the third trimester. Incontinence was re-assessed three months postpartum. Logistic regression analysis was used to assess the role of maternal and obstetric factors in causing postpartum urinary incontinence. This prospective cohort study in 949 pregnant women in Quebec, Canada was nested within a randomised controlled trial of prenatal perineal massage.

Results
Postpartum urinary incontinence was increased with prepregnancy incontinence (adjusted odds ratio [adj0R] 6.44, 95% CI 4.15, 9.98), incontinence beginning during pregnancy (adjOR 1.93, 95% CI 1.32, 2.83), and higher prepregnancy body mass index (adjOR 1.07/unit of BMI, 95% CI 1.03,1.11). Caesarean section was highly protective (adjOR 0.27, 95% CI 0.14, 0.50). While there was a trend towards increasing incontinence with forceps delivery (adjOR 1.73, 95% CI 0.96, 3.13) this was not statistically significant. The weight of the baby, episiotomy, the length of the second stage of labour, and epidural analgesia were not predictive of urinary incontinence. Nor was prenatal perineal massage, the randomised controlled trial intervention. When the analysis was limited to women having their first vaginal birth, the same risk factors were important, with similar adjusted odds ratios.

Conclusion
Urinary incontinence during pregnancy is extremely common, affecting over half of pregnant women. Urinary incontinence beginning during pregnancy roughly doubles the likelihood of urinary incontinence at 3 months postpartum, regardless whether delivery is vaginal or by Caesarean section.

 

Background
Bearing children is known to increase the likelihood of urinary incontinence, but which aspects of pregnancy and delivery cause urinary incontinence have not been clearly established. The role of pregnancy itself, independent of labor and delivery practices, in causing incontinence has not been adequately recognized. The risk of urinary stress incontinence is known to increase throughout pregnancy [1]. While most women incontinent during pregnancy will regain continence postpartum, those with postpartum incontinence will almost always have been incontinent during pregnancy [1-3].

The objectives of this study were to identify maternal and obstetrical factors associated with developing urinary incontinence during pregnancy; to descllalabribe the prevalence and severity of postpartum urinary incontinence; and to identify factors associated with postpartum incontinence.

Methods
Information for this study was collected during a randomised controlled trial of perineal massage during the third trimester of pregnancy [4,5]. The study population consisted of pregnant women with or without a previous vaginal birth delivering in five secondary and tertiary care hospitals in the province of Quebec, Canada. The study was approved by the ethics committees of each participating institution. Women were enrolled at 30 and 35 weeks gestational age. In the intervention group, women were taught to do a stretching massage of the perineum for 5 to 10 minutes daily from 34–35 weeks gestation until delivery; women in the control group were asked to refrain from perineal massage. There were 1527 women enrolled between September 1994 and December 1995. At enrolment, participants completed a questionnaire on socio-demographics and obstetrical history. Women recruited after March 1995 (n = 1198) also completed a self-administered questionnaire on perineal functions during the month before conception and during the month before enrolment (i.e. early third trimester of pregnancy.) The questionnaire elicited information on the frequency (never, less than once per week, 1–6 times a week, once a day, more than once a day) of involuntary loss of urine when coughing, sneezing, laughing, or running. We asked this quantitative question about the frequency of stress incontinence since we were interested in the pathophysiology – actual episodes of urine loss – rather than the social impact of incontinence. At three months postpartum, a questionnaire was mailed to each participant asking about stress urinary incontinence at that point in time. Detailed data on the occurrence and severity of perineal lacerations and episiotomy were recorded immediately after the birth by the attending physician or house staff. The perineum was considered to be intact if there was no laceration or a non-sutured first-degree tear. Other information about the labour and delivery was abstracted from the medical record.

For the analysis of predictors of incontinence, incontinence was treated as dichotomous: any vs. no incontinence. Secondary analyses were carried out restricting the outcome to more severe incontinence – at least weekly and at least daily. To assess urinary incontinence before delivery as a predictor of postpartum incontinence, a categorical variable was constructed with 3 levels: women with incontinence pre-pregnancy (95% continued to be incontinent during pregnancy), new onset of incontinence during pregnancy, and no incontinence before or during this pregnancy. Maternal, obstetrical and new-born candidate variables for the adjusted models were identified by univariate odds ratios (OR) <0.8 or >1.25 in association with urinary incontinence, or from the medical literature. Univariate and adjusted odds ratios (adjOR) and their 95% confidence intervals (95% CI) were obtained. Adjusted odds ratios from logistic regression analysis somewhat overestimate relative risk when the outcome is common. Since episiotomy and operative delivery are determinants ("in the causal pathway") of perineal trauma, separate models were used to analyse whether incontinence was better predicted by these interventions or by the degree of perineal trauma. Univariate, stratified and logistic regression analyses were carried out using Stata 7.0.

Results
Postpartum questionnaires were returned by 949 (79%) of 1198 women. These women constitute the study population, which has been described in a previous publication [5]. Baseline maternal characteristics of responders and non-responders to the postpartum questionnaire were similar in most respects although women who did not return their postpartum questionnaires were slightly younger (mean age, 28.6 vs. 29.8 yr.), less educated (mean educational level, 14.3 vs. 15.8 yr.) and more likely to have given birth by Caesarean section (17.7% vs. 12.0%). There was no difference in the proportion of responders between the perineal massage and control groups.

Urinary incontinence was experienced by 22.3% of women before pregnancy, 65.1% during the third trimester, and 31.1% three months after delivery. Table 1 details the frequency of urinary incontinence before, during and after pregnancy in women delivering by Caesarean section or having a first or a subsequent vaginal birth. Only 10 women were delivered by Caesarean after a previous vaginal birth; we excluded them from further analysis, since they were too few to provide reliable estimates of effect. The proportion of primiparous women delivered by Caesarean who experienced urinary incontinence before (16.3%) and during pregnancy (55.8%) was similar to that of primiparous women who delivered vaginally (16.1 and 58.9%, respectively.) Postpartum though, 31.2% of women were still incontinent after vaginal births compared to only 11.5% of women after Caesarean (OR 3.48, 95% CI 1.85, 6.54.) Of women expecting a first vaginal birth who remained continent during pregnancy, 20.6% were incontinent after vaginal delivery compared to only 6.6% after Caesarean (OR 3.64, 95% CI 1.07, 12.34). Most (81.8%) of the women with postpartum urinary incontinence were already incontinent before giving birth: 40.3% (119/295) were already incontinent before pregnancy, 40.7% (120/295) developed incontinence by the third trimester, and 18.0% (53/295) between study enrolment and completion of the postpartum questionnaire (third trimester data missing for a few individuals.

Urinary incontinence occurred at least daily in 26/835 (3.11%) of women after vaginal birth and in 1/114 (0.88%) following Caesarean birth (risk difference 2.2%, 95% CI 0.2%, 4.3%). However, compared to those delivering by Caesarean, women delivering vaginally were more likely to have at least daily incontinence before (2.0% vs. 0.9%) and during (10.5% vs. 8.8%) the pregnancy, not just after giving birth (NS).

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