Our aim was to describe risk factors associated with 34DPT in operative and non-operative vaginal deliveries, over a five-year period.

This was a retrospective cohort study including 39,227 vaginal deliveries from 2013 to 2017 in a single French University Hospital. Annual characteristics of the analyzed population were recorded. Univariate logistic regression was used to evaluate the association between these characteristics and 34DPT. Multivariate analysis was used to identify combinations of risk factors associated with instrumental delivery.

The rate of perineal tears was constantly rising but rate of 34DPT was stable, ranging between 0.8 and 1.4% over the study period. Cesarean section rate was stable between 18.8% and 19.6%. Rate of diabetes, preeclampsia and obesity (BMI < 40) was increasing and episiotomy rate decreasing (from 19.8% to 11.8%). Operative deliveries rate remained stable between 11 and 12.8%. Multivariate regression showed that gestational age over 39 weeks (aOR 1.18, 95% CI [1.02; 1.35]), birth weight over 3500 g (aOR 1.62, 95% CI [1.05; 2.49]) were associated with 34DPT in patients without operative vaginal deliveries but not episiotomy. Gestational age (aOR 1.71, 95% CI [1.18; 2.47]), episiotomy (aOR 0.55, 95% CI [0.38; 0.79]) and diabetes (aOR 1.73, 95% CI [1.15; 2.61]) were associated with 34DPT among patients with operative vaginal deliveries.

In a tertiary medical center model with low cesarean section rate, factors associated with 34DPT were different among patients with or without operative vaginal delivery. The question of the protective effect of mediolateral episiotomy against 34DPT in case of operative delivery deserves further investigations.