Objective To dynamically observe and evaluate the position and movement of pelvic floor organs in vaginal delivery primipara with translabial two-dimensional(2D) ultrasound,and to provide the imaging basis for the effects of pregnancy and vaginal delivery on the pelvic floor support structures.Methods Translabial 2D ultrasound was performed on 52 vaginal delivery postpartum women (postpartum group) and 43 normal women as control group to observe the position and movement of pelvic floor organs at rest,on pelvic muscle contraction and during maximum Valsalva maneuver.Results The location of urethrovesical junction and cervix were significantly lower in postpartum group compared with the control group at three stages.The movement of urethrovesical junction and cervix in vertical direction was greater in postpartum group than control group during maximum Valsalva maneuver,while was smaller on pelvic floor contraction.Conclusions Translabial 2D ultrasound could dynamically observe and evaluate the position and movement of pelvic floor organs.Pregnancy and vaginal delivery produce certain effect on pelvic floor support structures,which manifest as weak,defective and dysfunction.The impact was more obvious in anterior and middle compartments.