Objective: To investigate whether perineal wound complications in the first birth, alone or in conjunction with obstetric anal sphincter injury (OASI), is associated with an increased risk of OASI in the second birth.
Design: Nationwide population-based cohort study.
Setting: Sweden.
Population: Women (n = 411 317) with first and second singleton vaginal births in Sweden, 2001-2019.
Methods: Data on diagnostic codes and surgical procedures were retrieved from the Swedish Medical Birth Register and the Swedish Patient Register. A perineal wound complication was defined as wound infection, dehiscence or perineal haematoma within 2 months of childbirth.
Main outcome measures: Associations between wound complications in the first birth and OASI in the second birth were investigated with logistic regression and presented as adjusted odds ratios (aORs) with 95% confidence intervals (95% CIs).
Results: In total, 2619 (0.6%) women had a wound complication in the first birth, and 5318 (1.3%) had an OASI in the second birth. Women with a wound complication but no OASI in the first birth had more than doubled odds of OASI in the second birth (aOR 2.73, 95% CI 2.11-3.53). Women with OASI and a wound complication in the first birth had almost tenfold odds (aOR 9.97, 95% CI 6.53-15.24) of recurrent OASI.
Conclusions: Perineal wound complication in the first birth increases the likelihood of OASI in a subsequent birth.
Keywords: OASI; obstetric anal sphincter injury; perineal wound complication.
© 2024 The Authors. BJOG: An International Journal of Obstetrics and Gynaecology published by John Wiley & Sons Ltd.