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 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 stress incontinence before, during and 3 months after pregnancy in 835 women delivering vaginally without or with a previous vaginal birth, and in 104 primiparous women delivering by Caesarean.*
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).
New onset of urinary incontinence during pregnancy was more frequent in parous compared to nulliparous women (OR 1.95, 95% CI 1.42, 2.67). However maternal age, body mass index, weight gain during pregnancy, or factors potentially related to connective tissue properties, such as hair colour and stretch marks (data not shown) did not help to predict which women would develop urinary incontinence during pregnancy.
Postpartum urinary incontinence (three months after delivery) was independently associated with incontinence present before becoming pregnant and incontinence beginning during pregnancy (Table ), even among women undergoing Caesarean birth. Postpartum urinary incontinence was associated strongly with high prepregnancy body mass index (7% for each unit of body mass index). Once pre-pregnancy incontinence was taken into account, parous women were not more likely than nulliparous women to be incontinent postpartum (see stratified analysis, Table ). Caesarean section was protective (Table ). The following factors were not significantly associated with postpartum urinary incontinence in adjusted (multivariate) models: age, weight gain during pregnancy, baby's weight, previous vaginal birth, randomization group (massage or control), type of delivery, epidural anesthesia, duration of second stage of labor, episiotomy (Table ) or degree of perineal trauma or periurethral tears (data from this model not shown).
Risk factors for any urinary incontinence three months postpartum
Proportion of women with urinary incontinence 3 months postpartum
We repeat these analyses with 'incontinence at least weekly' instead of 'any incontinence' as the outcome; the same predictors were significant. Too few subjects had incontinence at least daily (n = 27) for stable estimates of odds ratios. Analyses restricted to women having a first vaginal birth yielded the same predictors as analysis with all parities combined.
Incontinence worse after delivery than in the third trimester occurred in only 9.7% (91/943) of women. Worse incontinence occurred in 3.5% (4/114) of women after Caesarean (adjOR 0.28, 95% CI 0.09,0.85) compared with 10.5% (87/829) after vaginal delivery. Maternal body mass index (adjOR 1.06 per unit of BMI, 95% CI 1.01, 1.11) was significantly associated with worsening of incontinence peripartum. Worsening tended to be more likely after forceps deliveries (adjOR 1.83, 95% CI 0.99,3.37) than after vacuum extraction (adjOR 1.33, 95% CI 0.73,2.42) or spontaneous delivery. Maternal age, baby's weight, length of the second stage, episiotomy, periurethral lacerations and degree of perineal trauma did not predict significant peripartum worsening of urinary incontinence.