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Segmental duplications and monosomies are linked to in vitro developmental arrest

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By : Dr. Laura Melado Vidales Prof. Dr. Barbara Lawrenz, PhD Prof. Dr. Human Fatemi Neelke De Munk Ibrahim El Khatib Asian Bayram Alberto Linan Ana Arnanz

Abstract
Purpose: To verify which genetic abnormalities prevent embryos to blastulate in a stage-specific time.

Methods: A single center retrospective study was performed between April 2016 and January 2017. Patients requiring Preimplantation Genetic Testing for Aneuploidies (PGT-A) by Next Generation Sequencing (NGS) were included. All embryos were cultured in a time-lapse imaging system and single blastomere biopsy was performed on day 3 of development. Segmental duplications and deletions as well as whole chromosome monosomies and trisomies were registered. Embryo arrest was defined if the embryo failed to blastulate 118 h post-injection. A logistic regression model was applied using the time to blastulate as the response variable and the different mutations as explanatory variables. A p value < 0.05 was considered significant.

Results: Of the 285 biopsied cleavage stage embryos, 103 (36.1%) were euploid, and 182 (63.9%) were aneuploid. There was a significant difference in the developmental arrest between euploid and aneuploid embryos (8.7% versus 42.9%; p = 0.0001). Segmental duplications and whole chromosome monosomies were found to have a significant effect on developmental arrest (p = 0.0163 and p = 0.0075), while trisomies and segmental deletions had no effect on developmental arrest. In case of segmental duplications, an increase of one extra segmental duplication increases the odd of arrest by 159%. For whole chromosome monosomies, the odd will only increase by 29% for every extra chromosomal monosomy. Both chromosomal abnormalities remained significant after adding age as an explanatory variable to the model (p = 0.014 and p = 0.009).

Conclusion: Day 3 cleavage stage embryos with segmental duplications or monosomies have a significantly decreased chance to reach the blastocyst stage.

Keywords: Blastocyst formation; Developmental arrest; Monosomy; PGT-A; Segmental duplication; Whole chromosome.

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