Study design, materials and methods
Participants in a previous cohort study who gave birth to their first child in two separate hospitals between 2009 and 2010 were contacted in follow-up studies one and six years after their first delivery. Women reported on UI symptoms on the ICI-Q SF questionnaire at both time points. Participants responding at both one and six years after first delivery were categorized into one of two groups, -continent or experiencing UI six years after first delivery (ICI-Q SF >=1). Prevalence of UI with 95% confidence interval was calculated. The chi-squared test or Mann-Whitney U test was used to compared background data as appropriate, and the Student´s t-test for paired data was used to compare ICI-Q mean scores at both time points. Multiple logistic regression analyses were applied to explore possible risk factors for UI six years after first delivery.
Of the 1031 women responding one year after first delivery, 615 (60%) responded at six years. Mean age among all participants at one year was 28.2 (SD: 4.5) years. There was no significant difference between non- responders and responders at six years after delivery with regards to mean age, mode of first delivery, grade of perineal tear at first delivery, and total ICI-Q score at one year after first delivery. However, there was a significant difference in educational level and marital status (p=<.001). A total of 55 % of the women participating six years postpartum reported UI, as compared to 38% one year postpartum. Within the group reporting UI six years postpartum, there was a significant increase (p=<.001) in mean ICI-Q score from 3.2 points (SD: 3.6) one year postpartum to 5.6 points (SD: 5.0) five years later. Six years after first delivery, one in four of the incontinent women (26%) reported low UI (ICI-Q score 1-3 points), 66% moderate UI (ICI-Q score 4-5 points) and 34% high UI (ICI-Q score 6 points and above). In addition, more women in the UI group had higher severity of UI one year after first delivery as well vaginal or instrumental first deliveries, whilst the continent group had more caesarean sections (Table 1). The UI group performed significantly more pelvic floor muscle training (PFMT) than the continent group (p<.05), and there was a significant association between experiencing UI and PFMT at six years after first delivery. Furthermore, UI symptoms one year after first delivery was associated with an increased risk for UI five years later (Table 2).
Interpretation of results
The prevalence of UI increased significantly from one to six years after first delivery, and more than 50% reported long term UI. Women experiencing UI one year after first delivery were at increased risk of UI five years later, and women with high symptom severity was at higher risk of long term UI compared to women reporting low or moderate symptom severity. Women experiencing UI were 60% more likely to perform PFMT weekly or more than continent women.