Objective: The aim of this study was to evaluate the effect of using uterine fundal pressure during the second stage of delivery on obstetric anal sphincter injury (OASI), among primiparous women using three-dimensional transperineal ultrasonography. Design: Case control study Setting: Tertiary Urogynecology Unit Population: Nulliparous women with term, singleton, cephalic presentation gestation delivered with fundal pressure in second stage of labour. Main Outcome Measure: Complete, incomplete IAS and EAS defect in transperineal tomographic ultrasound imaging Method: A total of 73 women who had their first vaginal birth were included in the study, 37 of them applied fundal pressure and 36 of them delivered spontaneously without fundal pressure. Tomographic ultrasound imaging with 3D transperineal assessment was performed within 48 h of delivery, IAS and EAS defect were determined. Results: Five (13.5%) women in the fundal pressure group, 7 (20%) women in the control group had complete EAS (p = 0.4). Complete IAS was observed in 1 (2.7%) women in the fundal pressure group and 2 (5.7%) women in the control group (p = 0.5). Half-moon sign was observed in 1 woman in both groups (p = 0.9). The rate of other signs were similar in both groups. Multivariate regression models revealed that none of, age, episiotomy, length of second stage of labour, fundal pressure application status and number were independent predictor of complete IAS or EAS defect. Conclusions: Fundal pressure during the second stage of delivery is not cause increase in rate of OASI detected with ultrasonography.