Objective To study the association between pelvic floor dysfunction (PFD) and mode of delivery and to calculate the risks of PFD comparing caesarean delivery and operative vaginal delivery to normal vaginal delivery 15-23 years after childbirth. A subgroup analysis comparing forceps and vacuum delivery was planned.Design Cross-sectional study.Setting Postal questionnaire.Population 1641 (53%) of 3115 women who delivered their first child in Trondheim, Norway, between January 1990 and December 1997.Methods A questionnaire including questions on symptomatic pelvic organ prolapse, urinary and fecal incontinence and surgery for these conditions.Main outcome measures Prevalence of PFD measured by symptomatic pelvic organ prolapse or surgery (sPOP), urinary incontinence or surgery (UI) and fecal incontinence or surgery (FI).Results When caesarean delivery was compared to normal vaginal delivery the adjusted odds ratio (aOR) for sPOP was 0.42 (95% confidence interval, CI, 0.21-0.86) and the aOR for UI was 0.65 (95% CI 0.46-0.92). Operative vaginal delivery was associated with increased risk of sPOP (aOR 1.73, 95% CI 1.21-2.48) and FI (aOR 1.96, 95% CI 1.26-3.06) when compared with normal vaginal delivery. There were no differences in sPOP, UI or FI in a subgroup analysis comparing forceps and vacuum delivery.Conclusions Caesarean delivery was associated with decreased risk and operative vaginal delivery with increased risk of pelvic floor dysfunction 15-23 years after first delivery, but there were no differences between forceps and vacuum delivery.Keywords Fecal incontinence, forceps delivery, pelvic floor dysfunction, pelvic organ prolapse, urinary incontinence, vacuum delivery.Linked article This article is commented on by R Rogers, p. 972 in this issue. To view this mini commentary visit http:// dx.doi.org/10.1111/1471-0528.13318.Please cite this paper as: Volløyhaug I, Mørkved S, Salvesen Ø, Salvesen KÅ . Pelvic organ prolapse and incontinence 15-23 years after first delivery: a crosssectional study . BJOG 2015;122:964-971.