Objective:To assess the role of the uterine artery blood flow in the prediction of implantation in women undergoing embryo transfer during the periimplantation period.Methods:A total of 233 couples were included in this prospective study.All patients had embryo transfer,125 were performed inin-vitro fertilization/intracytoplasmic sperm injection(IVF/ICSI) and108 in cryo cycles.Ultrasound measurements were performed immediately before transfer.The pulsatility index(PI),Resistance index(RI) and the peak systolic velocity(PSV) were measured in both uterine arteries using endovaginal ultrasound.Results:InIVF/ICSI cycles the doppler parameters PI(2.48vs.2.15),RI(0.78vs.1.30) andPSV(60 vs.63) did not differ significantly between the pregnant and non-pregnant group.The pregnancy rate per transfer was similar in women showing an unilateral(24%), bilateral(33%) or no(27%) notch in the uterine blood flow.In cryo cycles the uterine artery blood flow parametersPI(3.2vs.3.0),RI(0.9vs.0.9) andPSV(53.2vs.51.2) did not differ either between pregnant and not pregnant patients.Conclusions:Previous studies were aiming at the measurement of arterial doppler parameters during the follicular phase which may not be adequate for the prediction of implantation.However, our results show that doppler studies during the early luteal phase of assisted reproductive technology cycles are not indicative for the likelihood of pregnancy, too.