Preimplantation genetic testing for aneuploidy and chromosomal structural rearrangement: A summary of a nationwide study by the Japan Society of Obstetrics and Gynecology

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Purpose: The Japan Society of Obstetrics and Gynecology conducted a nationwide clinical study to evaluate the pregnancy outcomes of preimplantation genetic testing for aneuploidy or chromosomal structural rearrangement (PGT-A/SR). Methods: Patients that had experienced recurrent implantation failure, recurrent pregnancy loss, or chromosomal structural rearrangement were recruited from 200 fertility centers in Japan. For patients in whom one or more blastocysts were classified as euploid or euploid with suspected mosaicism, a frozen-thawed single embryo transfer (ET) was performed. Results: A total of 10 602 cycles, maternal age 28-50 years, were enrolled in this study. 42 529 blastocysts were biopsied, and 25.5%, 11.7%, and 61.7% of embryos exhibited euploidy, mosaicism, and aneuploidy, respectively. At least one euploid blastocyst was obtained in 38.3% of egg retrieval cycles with embryo biopsy. A total of 6080 ETs were carried out, and the clinical pregnancy rate per ET, ongoing pregnancy rate per ET, and miscarriage rate per pregnancy were 68.8%, 56.3%, and 10.4%, respectively. The rates of clinical pregnancy and miscarriage remained relatively constant across all maternal ages. Conclusions: Preimplantation genetic testing for aneuploidy or chromosomal structural rearrangement may improve the pregnancy rate per ET and reduce the miscarriage rate per pregnancy, especially in patients of advanced maternal age.