Imaging the endometrium: are there predictors of uterine receptivity?

Ultrasound imaging technology brings new insight to cyclic changes in the endometrium and offers the potential to assess the probability of embryo implantation in natural and assisted reproduction cycles. However, the data reported are diverse and frequently conflict in their analysis and conclusions. This review examines imaging techniques used for endometrial evaluation, including grey-scale ultrasonography and colour-flow, power-flow, and spectral Doppler interrogation of the uterine vasculature. New techniques being used for uterine assessment, such as computer-assisted image analysis, three-dimensional ultrasonography, and magnetic resonance imaging, are also discussed. Each of these techniques is under active investigation and has the potential to provide rapid, noninvasive endometrial evaluation. Currently, there is reasonable certainty that women with heterogeneous endometrial linings of less than 6 mm will rarely conceive, and that endometrial contractions, or lack thereof, play some role in the successful establishment of pregnancy, even though this role has not yet been identified. Given the set of new imaging technologies available, it is feasible to expect that visual assessments will someday be used as predictors of uterine receptivity.