Background: A good blood supply to the endometrium is usually considered as an essential requirement for implantation.
Objective: The aim of this study was to evaluate the role of endometrial and subendometrial vascularity in the prediction of pregnancy during frozen-thawed embryo transfer (FET) cycles.
Methods: Women undergoing FET in natural or clomiphene-induced cycles after the first stimulated IVF treatment were recruited. A three-dimensional (3D) ultrasound examination with power Doppler was performed 1 day after the LH surge to determine endometrial thickness, endometrial pattern, pulsatility index (PI) and resistance index (RI) of uterine vessels, endometrial volume, vascularization index, flow index and vascularization flow index of endometrial and subendometrial regions.
Results: Women in the pregnant group were significantly younger and used less gonadotrophins in their stimulated cycle. Endometrial thickness, endometrial volume, endometrial pattern, uterine PI, uterine RI, endometrial and subendometrial 3D power Doppler flow indices were similar between the nonpregnant and the pregnant groups. The age of women was the only predictive factor for pregnancy. Receiver operating characteristic curve analysis revealed that the area under the curve was around 0.5 for all ultrasound parameters for endometrial receptivity.
Conclusion: Vascularity of endometrial and subendometrial layers measured by 3D power Doppler ultrasound is not a good predictor of pregnancy in FET cycles if measured at one time point only.