Pregnancy, not childbirth, causes pelvic floor dysfunction

Abstract

Several small studies of samples of women attending a single gynaecological unit suggest that urinary and anal incontinence can be prevented by elective caesarean section, but Alastair MacLennan and his colleagues (pages 1460–1470) refute this notion. The authors carried out a large population survey, again in South Australia, to determine the prevalence of urinary and anal incontinence and other features of pelvic floor dysfunction, in men and in women. The main strengths of the study are its design and its size, for the method of selection of the participants minimised bias, and the large number of participants enabled the authors to make some precise estimates of the effects of putative causative factors. Pelvic floor dysfunction was defined as urinary incontinence (stress or urge); anal incontinence (flatus or faeces); symptoms of prolapse; or an operation for prolapse or urinary incontinence. Any one of these criteria constituted pelvic floor dysfunction Women experienced urinary and anal incontinence much more frequently than men. There was a linear trend in the frequency of pelvic floor dysfunction with nullipar-ity, caesarean section, spontaneous vaginal delivery and instrumental vaginal delivery. In a univariate analysis pelvic floor dysfunction was less frequent after caesarean section than spontaneous vaginal delivery, but this difference disappeared in multivariate analysis, which also showed that pelvic floor dysfunction was more common with instrumental vaginal delivery. There was no difference in the frequency of pelvic floor dysfunction, whether delivery was by elective caesarean section or by caesarean section during labour. It may be thought that since the diagnosis of pelvic floor dysfunction was by self-reporting the symptoms experienced by the women may not have been severe; this is not the case, however, since measurement of quality of life by the Short Form-36 showed that women with pelvic floor dysfunction suffered significant physical and mental distress. What is remarkable about this paper is not so much the comparisons between the various types of delivery, but the frequency of pelvic floor dysfunction in the population. Thus one in eight women who have never been pregnant had some form of pelvic floor dysfunction, compared with one half of the women who had a caesarean section or a spontaneous vaginal delivery and two-thirds of the women who underwent an instrumental vaginal delivery. MacLennan and colleagues describe this as an epidemic. It is likely that the frequency of pelvic floor dysfunction in this population of Australian women is typical of all women who undergo childbirth. The authors conclude that it is pregnancy which is responsible for pelvic floor dysfunction, and not childbirth, unless this is compounded by instrumental vaginal delivery; and suggest that caesarean section will not reduce the risk of pelvic floor dysfunction, except where instrumental vaginal delivery can be avoided