Chromosomal aneuploidy is recognized to be a significant contributing factor in implantation failure and spontaneous miscarriage Hellani et al.

Objective: To define criteria for determining when preimplantation genetic testing for aneuploidy (PGT-A) results are suggestive of a potential balanced chromosomal rearrangement in the egg or sperm source and warrant karyotyping. Design: Performance evaluation of criteria developed to assess PGT-A results for patterns of imbalances suggestive of a balanced chromosomal rearrangement in the egg or sperm source. Setting: A single PGT-A laboratory and multiple in vitro fertilization centers. Patients: Reproductive couples who underwent routine PGT-A testing. Interventions: Karyotyping of reproductive couples for whom patterns of imbalances observed in PGT-A results suggested a balanced chromosomal rearrangement in the egg or sperm source. Main Outcome Measures: Correct or incorrect flagging of predicted translocation in either the egg or sperm source based on chromosome analysis. Results: Proposed criteria correctly predicted a balanced reciprocal translocation in 97% of cases (n ¼ 33), a (13;14) Robertsonian translocation in all cases (n ¼ 3), and an inversion in all cases (n ¼ 2). Other criteria evaluated were determined to be ineffective because of relatively low occurrences that met the criteria and/or low predictive value. Conclusions: Our results showed that the proposed criteria were effective for evaluating patterns of imbalances observed in PGT-A results suggestive of a potential chromosomal rearrangement in the egg or sperm source. Our proposed criteria can be employed by clinicians in the in vitro fertilization setting in combination with a patient's reproductive history to identify PGT-A patients who are likely carriers of balanced chromosomal rearrangements. (Fertil Steril Rep Ò 2021;2:72-9. Ó2020 by American Society for Reproductive Medicine.

While there are various testing methodologies that are best suited in cases of known parental rearrangements, tNGS offers enhanced identification of balanced rearrangement carriers compared to previous testing methodologies. Further, it provides an additional opportunity for diagnosis in patients that may be missed in the clinical setting. References: 1. Jacobs PA, Browne C, Gregson N, Joyce C, White H. Estimates of the frequency of chromosome abnormalities detectable in unselected newborns using moderate levels of banding.

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