Introduction A number of risk factors for third and fourth degree perineal tears or obstetric anal sphincter injury (OASI) have been identified, but the rate of recurrence is not consistent in the observational studies.

Aim To assess the rate of third degree tear following an OASI in the first pregnancy in a tertiary referral unit.

Methods Data was collected from maternity database, for women diagnosed with an OASI in their first pregnancy who went on to have a subsequent pregnancy at St. Michael’s hospital. Data collection period was between 2007–2012. Data was limited to term, singleton, cephalic deliveries in subsequent pregnancy.

Results 210 women met the criteria. 63 (30%) had an elective caesarean section and 147 (70%) opted for vaginal delivery. 10/147 (6.8%) required an emergency LSCS. 14/137 (10.2%) women who had a vaginal delivery sustained a further OASI. When comparing the women who had OASI to women who did not sustain an OASI in the subsequent pregnancy, there was no significant difference between the mean birth weights or the mode of onset of labour.

Conclusion Over the five year period the recurrence risk of OASI was low. This information can be used to advise women when discussing mode of delivery in subsequent pregnancies. Further research is needed into the pelvic floor symptom profile of the women who have a vaginal birth following an OASI in the first pregnancy.