Background : Accurately predicting the possibility of pregnancy during an in vitro fertilization (IVF) or intra-cytoplasmic sperm injection (ICSI) cycle has long been challenging.   
Aim of the Work : to determine whether the clinical pregnancy rate in IVF and ICSI cycles is affected by the alteration in endometrial thickness, volume, and perfu-sion between the end of the estrogen phase and the day of embryo transfer.  
Patients and Methods: The present study was a prospec-tive observational study conducted in the obstetrics and gynecology department of Mansoura University Hospi-tals, Mansoura, Egypt. The present study was conducted on 25 subfertile women undergoing IVF and ICSI cycles. Endometrial preparation with the use of progesterone was done for all patients. In these 25 women candidates for ICSI, endometrial thickness and sub-endometrial perfu-sion were measured with a trans-vaginal 2-dimensional ultrasound (2D U/S) and 3-dimensional power Doppler ultrasound (3D PD U/S), respectively, on the day of hu-man chorionic gonadotrophin (hCG) trigger and embryo transfer (ET).  
Results: When comparing instances with positive preg-nancy tests to those with negative pregnancy tests, there is a notable increase in endometrial volume and sub-endo-metrial vascularization flow index (VFI), corresponding to the occurrence of pregnancy on the day of the hCG trigger and the day of embryo transfer. The average uter-ine resistance index (RI) on the day of embryo transfer in positive pregnancy cases is considerably higher than in negative pregnancy instances, and it is also significantly higher on the day of embryo transfer compared to the day of HCG trigger in positive pregnancy cases. By contrast-ing cases in which pregnancies were positive with those in which they were negative, there is a significant increase in the average uterine pulsatility index (PI) on the days of embryo transfer and HCG trigger as well as on the day of embryo transfer when compared to the day of HCG trig-ger in positive pregnancy cases. 
Conclusion: Endometrial volume, sub-endo-metrial VFI, uterine RI, and uterine PI had an impact on the pregnancy outcome and clini-cal pregnancy rate in IVF and ICSI cycles.