“…The multivariate logistic regression allowed us to analyze together the effect of other risk factors and potential confounders (maternal age, parity, BMI before pregnancy, gestational age, induction of labor, epidural use, persistent occiput position, attempted operative vaginal delivery classification, delivery by attending obstetrician or registrar, instrument type, active phase of second stage longer than 30 minutes, indications for attempted operative vaginal delivery, birth weight, and episiotomy). [25][26][27][28] The propensity score analyses were performed as sensitivity analyses to confirm the results of the multivariate logistic regressions. The propensity score was based on a logistic regression model that included all the covariates that were significantly differently distributed according to whether the attempt was midpelvic or low pelvic.…”