Ramm O, et al. - In this work, the rate of obstetric anal sphincter injuries was delineated and key risk factors of obstetric anal sphincter injuries, including duration of the second stage of labor, were determined. Bivariate and multivariate analyses revealed that obstetric anal sphincter injury incidence was higher among women with second stage of labor longer than 2 hours, Asian race, nulliparity, vaginal birth after cesarean delivery, episiotomy, and vacuum delivery. The highest odds of obstetric anal sphincter injury followed by prolonged duration of the second stage of labor with vacuum-assisted vaginal delivery. With the goal of reducing obstetric anal sphincter injury incidence, understanding these risk factors and their complex interactions could inform antepartum and intrapartum decision-making.