Hypothesis / aims of study
Stress urinary incontinence (SUI) and genital prolapse (POP) affect many women and are strongly associated with vaginal childbirth. Each year, about 9 000 women have surgery for these conditions in Sweden. The primary aim of this study was to analyze the prevalence of surgery in relation to parity and mode of delivery. Secondary aims were to compare the satisfaction and cure rate of urinary incontinence and symptomatic POP one year after surgery in nulliparous women, and women exclusively delivered by cesarean section and in those with at least one vaginal delivery.
Study design, materials and methods
This was a prospective, register-based, nationwide study using two registers. The Swedish National Quality Register of Gynecological Surgery (GynOp) (1) which includes a preoperative and postoperative assessment. The second was the Total Population Register (TPR) of Statistics Sweden (2). Self-reported data on parity was retrieved from GynOp and was checked against information in the TPR. The TPR has almost full coverage (99.7%) and is continuously updated every sixth week. The GynOp register covers more than 98% of all gynecological surgical procedures in Sweden. Women aged ≥45 years, who had surgery for POP and/or SUI between 2010 and 2016, were included (n = 61,850). Given this size of study cohorts, an alfa level of 0.05, a power value of 80%, and using Student’s t-test for the analysis, the minimum significant difference between register groups was 5%. The questionnaire used by the GynOp register during workup for surgery, contained questions about height, weight, climacteric status, parity, number of births and mode of delivery, current symptoms of urinary incontinence and pelvic organ prolapse, and previous surgery for these conditions etc. In the postoperative questionnaire UI was defined as leakage once a week or more often. The symptom of POP was defined as a feeling of a “vaginal bulge” once a week or more often. Satisfaction with the procedure was affirmed by the answers “Satisfied” and “Very satisfied” and negated by the answers “Neither satisfied nor unsatisfied”, “Unsatisfied”, and “Very unsatisfied”. The national background population per year represented by women aged ≥ 45 years during the period 2007 to 2017 was retrieved from the TPR, and was reported to be about 2.2 million yearly. Three sub-sets of women were described and analyzed in this study: nulliparous women, women delivered by one or more cesarean section, and women with at least one vaginal delivery. The distribution of parity and mode of delivery in the proportion of women reporting symptoms of SUI and POP and satisfaction with the procedure one-year postoperatively were presented as numbers, percentages and 95% confidence intervals (CI). Fisher’s exact test was used for comparison of categorical variables. Trend between independent groups was analyzed with Mantel–Haenszel statistics. Statistical significance was set at P value < 0.05.
Surgical procedures for SUI and POP had been performed on 61,850 women during the period 2010-2017. Information about parity and mode of delivery was available for 85.0% (n = 52,555) in the GynOp cohort. Among these the mean parity was 2.4 while it was 2.0 in the background population. Nulliparous women accounted for 2.1% (n = 1,104) of all women and 0.6% (n = 374) of the parous women had been delivered exclusively by cesarean section and the remaining 97.3% in the GynOp cohort had experienced at least one vaginal delivery. The distribution of parity and mode of delivery was markedly different in the GynOp cohort compared with the background population (Figure 1). Nulliparous women were underrepresented in the GynOp cohort by a factor of almost seven (2.1% versus 13.8%). This was also the case for women delivered by cesarean section only, who were underrepresented by a factor of 17 (0.7%) in the GynOp cohort versus 11.8% in the background population. In the one-year assessment, nulliparous women were less satisfied with the result of the incontinence procedure and also had a higher rate of UI weekly and more often (Table 1).
Interpretation of results
Surgery for genital SUI and POP was almost exclusively performed on women after one or more vaginal deliveries. Nulliparous women had surgery for prolapse three times more often than women delivered exclusively by one and more cesarean sections. This indicates a different etiology for pelvic floor disorders in this group of women ≥ 45 years and previous reports have shown diverse pathogenetic factors such as connective tissue disorders (3), prolonged severe constipation and a history of traumatic injuries.