A Review of Non-invasive and Invasive Embryo Characteristics to Indentify the Most Competent Embryo for Transfer

Identifying “competent embryos” (those with the greatest potential to develop into normal concept) for transfer to the uterus has been a matter of the highest priority and the subject of both hot debate and ongoing research, since the very inception of human in vitro fertilization (IVF). A thorough literature search was performed to evaluate the correlation between pronuclear morphology, early embryo cleavage speed, cleavage stage embryos, embryo/blastocyst development, “omics”, sHLA-G expression, PGS, and implantation/pregnancy-generating potential in ART. Based on available literature, an array/combination of laboratory observations could assist the scientist with embryo selection. The pronuclear stage morphology, the early embryo division, cleavage embryo stage and quality of the day 3 embryos provides limited guidance. We conclude that use of (invasive) PGS in specific patient populations is appropriate; however, more data are needed to determine its true value for overall impact in ART. Non-invasive selection of blastocysts on day 5 with optimal sHLA-G expression provides a very high degree of confidence to yield a viable pregnancy and potentially reduce multiple gestations.