to describe the frequency, severity and persistence of dyspareunia in the first 18 months after the birth of a first child.prospective pregnancy cohort study.Melbourne, Victoria, Australia.1507 nulliparous women.women ≤24 weeks gestation were recruited from six public hospitals. Self-administered written questionnaires were completed at recruitment and at three, six, 12 and 18 months post partum.study-designed self-report measure of dyspareunia on first vaginal sex, and on second and subsequent sex at all time-points, utilising the rating scale from the McGill Pain Intensity Scale.overall, 961/1122 (85.7%) of women experienced pain on first vaginal sex postnatally. The proportion of women experiencing dyspareunia reduced over time, from 431/964 (44.7%) at three months post partum to 261/1155 (22.6%) at 18 months post partum. Of the women who reported dyspareunia at each time-point, around 10% of women described the pain as׳distressing׳,׳horrible׳ or׳excruciating׳. Women who had a caesarean section were more likely to report more intense dyspareunia at six months post partum (aOR=2.35, 95% CI=1.2-4.6).postnatal dyspareunia decreases over time, but persists beyond 12 months for one in five women. Caesarean section appears to be associated with more intense dyspareunia.