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. 2024 Dec;41(12):3357-3370.
doi: 10.1007/s10815-024-03278-4. Epub 2024 Oct 8.

Incidence of haploidy and triploidy in trophectoderm biopsies of blastocysts derived from normally and abnormally fertilized oocytes

Laura Girardi  1 , Cristina Patassini  2 , Jose Miravet Valenciano  3 , Yoshimi Sato  4 , Natalia Fagundes Cagnin  5 , Jose Antonio Castellón  6 , Francesco Cogo  2 , Paola Zambon  2 , David Blesa  3 , Jorge Jimenez Almazan  3 , Adedoyin Akinwole  7 , Bruno Coprerski  5 , Carmen Rubio  3
Affiliations

Incidence of haploidy and triploidy in trophectoderm biopsies of blastocysts derived from normally and abnormally fertilized oocytes

Laura Girardi et al. J Assist Reprod Genet. 2024 Dec.

Abstract

Purpose: We aimed to identify the correlation between morphological pronuclear (PN) status and the genetically determined ploidy configuration in preimplantation embryos.

Methods: A retrospective observational study was conducted on 1982 embryos displaying normal fertilization and 380 embryos showing an atypical PN pattern, tested for aneuploidies and ploidy status via preimplantation genetic testing (PGT) between May 2019 and May 2024. Ploidy prediction was performed using a validated targeted-NGS approach and a proprietary bioinformatic pipeline analyzing SNPs B-allele frequency information. Ploidy results were obtained in relation to the morphological PN pattern and further stratified by mode of PN observation, maternal age, and embryo quality parameters.

Results: Abnormal ploidy results in 2PN-derived embryos were 1% (n = 20/1982): 0.8% showed triploidy and 0.2% haploidy. Ploidy results in relation to PN number in atypical fertilization were as follows: 0PN (n = 150/380) associated with 87.3% of diploidy, 8.7% of haploidy, and 4.0% of triploidy; 1PN-derived blastocysts (n = 73/153) were haploid in 47.7% of cases, 6.5% were triploid, and 45.7% diploid; 2.1PN (n = 23/280) and 3PN patterns (n = 54/280) predicted a triploid result in 34.8% and 74.1% of cases, respectively. PN observation with time-lapse increased ploidy status predictivity from 28.3% to 80.4% (p < 0.01) and reduced expected diploid rates to 19.6% (p < 0.01). Diploidy rate was higher for maternal age ≤ 35 years and for morphologically high-grade embryos.

Conclusion: Morphological PN check can be improved by incorporating ploidy analysis within the conventional PGT workflow. Euploid 2PN-derived embryos can be further selected removing haploids and triploids, and some atypical PN pattern can be better classified.

Keywords: Fertilization; NGS; PGT; Ploidy; Pronuclei; Time-lapse.

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Conflict of interest statement

Declarations. Conflict of interest: All authors are employees of Igenomix, a company providing reproductive genetic services, part of Vitrolife Group.

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