Purpose of review: To give an overview of the current status and future directions of blastocyst transfer and outcome with particular focus on markers of blastocyst quality and their relationship with implantation.
Recent findings: In addition to morphological markers, future embryo grading systems, in general, and blastocyst grading systems, in particular, will be based upon metabolic, genetic and epigenetic markers that will increase their efficiency. Metabolic markers such as soluble human leukocyte antigen-G, analysis of specific gene mutations in the trophectoderm by real-time multiplex polymerase chain reaction and analysis by microarray of differential gene expression will be operational in the near future for accurate blastocyst grading and selection.
Summary: Gamete and embryo quality as well as culture conditions affect blastocyst formation and quality. Characteristics of the zygote and the cleavage-stage embryo determine the developmental potential of the embryo up to the blastocyst stage. There appears to be a strong relationship between blastocyst quality and implantation. Accurate grading is important for selection of the most implantation-competent blastocyst. Similar to grading systems used in the cleavage-stage embryo, current blastocyst grading systems are mainly based upon morphological characteristics. Incorporation of metabolic, genetic and epigenetic markers will undoubtedly improve the selection process, making it possible to transfer a single blastocyst yielding high pregnancy rates.