Impact of third- and fourth-degree perineal tears at first birth on subsequent pregnancy outcomes: a cohort study

ObjectiveTo investigate, among women who have had a third- or fourth-degree perineal tear, the mode of delivery in subsequent pregnancies as well as the recurrence rate of third- or fourth-degree tears. DesignA retrospective cohort study of deliveries using a national administrative database. SettingThe English National Health Service between 1 April 2004 and 31 March 2012. PopulationA total of 639402 primiparous women who had a singleton, term, vaginal live birth between April 2004 and March 2011, and a second birth before April 2012. MethodsMultivariable logistic regression models were used to estimate odds ratios, adjusted for other risk factors. Main outcome measuresMode of delivery and recurrence of tears at second birth. ResultsThe rate of elective caesarean at second birth was 24.2% for women with a third- or fourth-degree tear at first birth, and 1.5% for women without (adjusted odds ratio, aOR 18.3, 95% confidence interval, 95% CI 16.4-20.4). Among women who had a vaginal delivery at second birth, the rate of third- or fourth-degree tears was 7.2% for women with a third- or fourth-degree tear at first birth, compared with 1.3% for women without (aOR 5.5, 95% CI 5.2-5.9). ConclusionsThe risk of a severe perineal tear is increased five-fold in women who had a third- or fourth-degree tear in their first delivery. This increased risk should be taken into account when decisions about mode of delivery are made.