Little is known about the natural history of pelvic floor dysfunction (PFD). We investigated the association between prepregnancy and postnatal PFD in premenopausal primiparous women and the associated effect of mode of delivery.A prospective cohort study, nested within the parent Screening for Pregnancy Endpoints (SCOPE) study, was performed in a tertiary referral teaching hospital with approximately 9,000 deliveries per annum. The validated Australian pelvic floor questionnaire was completed by 872 nulliparous women at 15 weeks' gestation, at the time of recruitment to the SCOPE study and 1 year postnatally. The questionnaire contained four sections with questions about urinary, faecal, prolapse and sexual dysfunction.One year postnatally urinary dysfunction was present in 73 %, faecal in 49 %, prolapse in 14 % and sexual in 58 % of participants. Prepregnancy PFD persistent postnatally constituted more than half of total PFD. The majority of affected (71 %) had multicompartment involvement. Participants with persistent PFD had higher prevalence of severe symptoms and bothersome symptoms within the group. Severity of prepregnancy PFD worsened in < 15 % cases postnatally.The main damage to the pelvic floor seems to occur in the majority of patients before first pregnancy, where first childbearing does not worsen prepregnancy PFD in the majority of cases. Pregnancy appears to affect more pre-existing symptoms of urgency and urge incontinence comparing to stress incontinence. Caesarean section seems to be more protective against postnatal worsening of prepregnancy PFD comparing to de novo onset pathology. However, larger studies are needed to confirm these findings.