OBJECTIVE To investigate whether the pattern or pain or bleeding during levonorgestrel intrauterine system (LNG-IUS) insertion and in the first 6 weeks thereafter is altered by LNG-IUS malposition. METHODS Prospective cohort of 413 women undergoing LNG-IUS insertion or replacement. A first questionnaire on pain perception was completed by the women immediately after insertion. In a second questionnaire the women were asked to record pain in the 3 days following insertion and both pain and bleeding from 4 to 6 weeks after insertion. Six weeks after insertion a 2D- and 3D-ultrasound examination was performed to evaluate the position of the LNG-IUS and of the uterus. RESULTS Parity was inversely related to pain at insertion, in the first 3 days and at 4-6 weeks. LNG-IUS insertion was less painful in the postpartum period. Women who had had a LNG-IUS as prior contraceptive method reported a higher percentage of amenorrhea at 4-6 weeks. The position of the LNG-IUS or of the uterus did not influence the pain scores or the bleeding pattern. The fact that the LNG-IUS arms appeared embedded in the uterine wall on coronal 3D-volume reconstruction did not influence pain or the bleeding pattern. CONCLUSIONS Because neither pain nor bleeding is a reliable predictor of LNG-IUS position, we suggest an ultrasound examination to confirm correct LNG-IUS placement in all patients at about 6 weeks after insertion.