Pre‐implantation genetic testing: Past, present, future

BACKGROUND: Pre‐implantation genetic testing (PGT) has been performed worldwide since it was first used by Handyside et al in the United Kingdom to sex embryos in 1990. Until about 2010, cleavage stage embryo biopsy and fluorescent in situ hybridization (FISH) were mainstream; however, in 2012, blastocyst biopsy (trophectoderm; TE biopsy) became mainstream. In addition, array comparative genomic hybridization (aCGH) was used for analysis and further evolved to next‐generation sequencing (NGS), which is used worldwide. METHODS: PGT for reciprocal balanced translocation and Robertsonian translocation (PGT‐SR) was approved in Japan for habitual abortion to reduce pregnancy loss, and since 2008, we have been performing PGT‐SR using cleavage stage embryos and FISH. In 2014, we performed TE biopsy and NGS analysis. MAIN FINDINGS: In this paper, I separately described the details of our methods and clinical results of FISH and NGS. NGS is superior to FISH because it can detect all chromosomes. CONCLUSION: TE biopsy and NGS, which have recently become mainstream, have stable outcomes, because TE biopsy yields more cells and fewer mosaics than the cleavage stage. As a result, diagnoses are more reliable, resulting in higher pregnancy rates and lower abortion rates.