INTRODUCTION: Pelvic floor injury from obstetric trauma has been associated with increase in future pelvic floor dysfunction. Thus, analysis of factors in women who have had a third- or fourth-degree laceration may help to identify those at risk of developing pelvic floor dysfunction. Several factors such as operative vaginal delivery and median episiotomy have been shown to be risk factors for these lacerations. In this study we attempt search for additional risk factors for obstetric trauma. METHODS: We identified 100 women who had a third- and fourth-degree laceration and 100 randomly selected women in a control group from the same time period. Parity, presence of stretch marks, prepregnancy body mass index, age, smoking, fetal weight, operative vaginal delivery, median episiotomy, and duration of second stage were compared between each group. Odds ratios (ORs) were calculated for each of the listed risk factors. RESULTS: Prepregnancy body mass index greater than 30 kg/m (OR 5.3, P=.01), fetal weight greater than 4,000 g (OR 20.7, P=.01), duration of second stage between 1 and 2 hours (OR 10.8, PCONCLUSION: Of the listed risk factors, duration of second stage as little as 1 hour may increase the risk of obstetric trauma. This may represent a modifiable risk factor to decrease the risk of future pelvic floor dysfunction. Language: en