Non-Invasive Methodologies for Endometrial Evaluation in Medically Assisted Reproduction

A conceptual synopsis of the state of non-invasive image-based endometrial receptivity assessment methods utilized within in vitro fertilization (IVF) cycles is presented in narrative review format. Many methods for assessing the endometrial contribution to cycle outcome have been posited over the decades since IVF became a mainstream approach for treatment of infertility. Yet, understanding of the endometrial component remains incomplete and most methods for assessing endometrium in the context of IVF are subject to significant divides within the literature. The need for non-invasive, per-cycle approaches to assess endometrial receptivity is being addressed with innovative methods; and, incremental progress is laying a foundation for quantitative assessment of the many factors that contribute to endometrial receptivity. Non-invasive image-based assessments of the endometrium align on two key factors: 1) they make quantifiable assessments of specific endpoints; and, 2) they are conducted on a per-cycle basis which enables real-time clinical decision making. Herein we summarize endometrial thickness, endometrial pattern, uterine biophysical profiles, endometrial scoring, Doppler approaches, uterine contractility, endometrial length and volume, endometrial compaction, the ultrasound-based endometrial receptivity test, and artificial intelligence and machine learning approaches to assessment of endometrium. We also note and discuss the importance of accounting for embryo quality when making decisions focused on endometrial assessment methods since the two factors are intimately intertwined in successful establishment of pregnancy.