We identified 323 748 women who gave birth to a first and second child during the study period 2000–2014. Both births were restricted to live born, single neonates, born in cephalic presentation at gestational week 34 or later, without malformations (excluding all ICD‐10 Q‐diagnoses) in order to exclude common indications for prelabor cesarean delivery such as multiple pregnancy, breech presentation and malformation. To achieve a sample of women with a first birth with VE, we excluded women with spontaneous vaginal delivery, cesarean delivery, forceps delivery or combined instrumental delivery in the first birth. In total, 45 674 (14.1%) women had a first birth with VE (Figure 1).
The exposure lateral or mediolateral episiotomy was defined by a checkbox in the standardized maternal medical record marking a left‐ or right‐sided episiotomy. In total, 13 950 (31.2%) women had a lateral or mediolateral episiotomy and 30 706 (68.8%) had no episiotomy. Women with a midline (n = 209, 0.5%) or undefined type of episiotomy (with the procedure code TMA00 but no indication of side, n = 809, 1.8%) were excluded. The final cohort included 44 656 women with a lateral/mediolateral episiotomy or no episiotomy (Figure 1).