Severe perineal laceration during operative vaginal delivery: the impact of occiput posterior position

OBJECTIVE: To identify risk factors for severe (third/fourth degree) perineal laceration with operative vaginal delivery (OVD, forceps or vacuum). STUDY DESIGN: Case-control study comparing singleton OVDs with or without severe laceration (n=138). RESULT: In multivariable analyses, severe perineal laceration was associated with occiput posterior (OP) position at delivery, vaginal nulliparity, use of forceps, longer period pushing in the second stage and lower gestational age, but not birth weight, labor induction or episiotomy. Among 29 OP patients at full dilation, 9/13 (69%) attempted rotations to occiput anterior (OA) were successful, and 14/16 (88%) patients in whom rotation was not attempted remained OP at delivery. Successful rotation from OP to OA was associated with fewer severe lacerations than no attempt or unsuccessful rotation (22 vs 75%, P=0.01). CONCLUSION: Severe perineal laceration during OVD is associated with OP position at delivery and is reduced threefold in patients successfully rotated from OP to OA.