Several studies have investigated the importance of maternal, fetal factors and intrapartum characteristics in predicting severe perineal lacerations. The purpose of the present systematic review is to accumulate current evidence and provide estimated effect sizes for the various risk factors described. We reviewed Medline, Scopus, Clinicaltrials.gov, EMBASE, Cochrane Central Register of Controlled Trials CENTRAL and Google Scholar for published studies in the field for observational studies as well as randomized controlled trials. Two researchers independently assessed the included studies and documented outcomes. Data extraction was performed using a modified data form that was based in Cochrane`s data collection form for intervention reviews for RCTs and non-RCTs. Forty-three articles were selected for inclusion in the present systematic review. The analyzed population reached 716,031 parturient of whom 22,280 (3,1%) sustained third- and fourth-degree perineal lacerations. Several risk factors were identified. Instrumental delivery RR 3.38 (2.21, 5.18), midline episiotomy RR 2.88 (1.79, 4.65) and a persistent occiput posterior position RR 2.73 (2.08, 3.58) were associated with the higher risk of developing severe perineal lacerations. Mediolateral episiotomy did not increase, but was also not protective against perineal lacerations RR 1.55 (0.95, 2.53). Several factors contribute to the development of severe perineal lacerations. The present meta-analysis presents accumulated data that may help physicians estimate risks and provide appropriate patient counseling.