Webinar: Evaluating the Viability of Non-2PN Embryos with PGT

Webinar summary

In this webinar, Dr. Adam Pillon of Victory Reproductive Care presents an evaluation of non-two pronuclear (non-2PN) embryos within the context of preimplantation genetic testing for aneuploidy (PGT-A). The presentation reviews published laboratory and clinical evidence examining whether embryos traditionally excluded following fertilization assessment may represent viable candidates for continued culture and genomic evaluation when integrated ploidy assessment is incorporated into the workflow.

Presentation overview

The presentation examines current laboratory practice surrounding embryos exhibiting abnormal pronuclear (PN) numbers following fertilization assessment. Approximately 10% of fertilized oocytes demonstrate abnormal pronuclear numbers (0PN, 1PN, 3PN, or greater), and these embryos have traditionally been excluded based on morphological assessment alone.

The webinar reviews published studies evaluating:

• Diploidy rates among non-2PN embryos
• Blastocyst development
• Euploidy rates following PGT-A
• Implantation and live birth outcomes
• Laboratory mechanisms underlying abnormal pronuclear morphology

The discussion proposes integrating genomic ploidy assessment into existing laboratory workflows to evaluate embryos that would otherwise be discarded based solely on morphology.

Key findings

Pronuclear morphology alone does not predict genomic status

• Traditional fertilization assessment classifies embryos based on pronuclear number, yet this represents a morphological rather than genetic observation
• The presentation highlights that conventional 2PN embryos can exhibit abnormal ploidy despite normal morphology
• Conversely, non-2PN embryos may retain normal diploid genomic content

Published studies demonstrate high diploidy rates among non-2PN embryos

• Multiple published studies reported substantial proportions of non-2PN embryos as diploid following PGT-A
• Approximately 80% of non-2PN embryos were reported as diploid in one large cohort
• Zero-pronuclear (0PN) embryos demonstrated diploidy rates approaching those observed for conventional 2PN embryos, while one-pronuclear (1PN) embryos showed somewhat lower but still substantial diploidy rates

Developmental competence was observed following genetic assessment

• Zero-pronuclear embryos demonstrated blastocyst development rates comparable to conventional 2PN embryos
• Published data also reported implantation and live birth outcomes for genetically confirmed diploid non-2PN embryos that were like those observed in diploid 2PN embryos
• One-pronuclear embryos exhibited lower developmental performance but retained measurable implantation and live birth potential

Euploid embryos were identified within non-2PN populations

• Published PGT-A studies demonstrated that a substantial proportion of genetically confirmed diploid non-2PN embryos were also euploid
• Euploidy frequencies approached those observed in conventionally fertilized embryos within the evaluated cohorts
• These findings indicate that morphologically abnormal fertilization does not necessarily correspond to chromosomal abnormality

Laboratory mechanisms may explain non-2PN diploidy

• The presentation reviews several biological mechanisms that may account for diploid non-2PN embryos
• For one-pronuclear embryos, published evidence suggests that both parental genomes may be incorporated within a single pronucleus in approximately half of evaluated cases
• For 2.1PN embryos, the presence of micronuclei does not necessarily indicate excess genomic material, as studies reported all evaluated 2.1PN embryos remained diploid

PGT-A combined with ploidy assessment expands embryo evaluation

• Standard copy number analysis identifies chromosome dosage but cannot distinguish heteroparental diploidy from uniparental diploidy
• The presentation proposes combining conventional PGT-A with SNP-based ploidy assessment to confirm both diploidy and biparental inheritance
• This integrated approach provides additional genomic characterization for embryos previously excluded based on morphology alone

Integrated clinical and laboratory workflows were proposed

• The presentation emphasizes collaboration between embryology laboratories and clinical teams when incorporating genomic evaluation into embryo selection workflows
• Future workflow considerations include expanded embryo culture, integrated PGT-A with ploidy assessment, laboratory quality improvements, AI-assisted pronuclear evaluation, and emerging non-invasive genomic approaches

This presentation reviews published evidence supporting genomic evaluation of non-2PN embryos through integrated PGT-A and ploidy assessment rather than exclusion based solely on visual morphological assessment. The reviewed studies demonstrate that substantial proportions of non-2PN embryos are diploid and that genetically characterized embryos may exhibit developmental outcomes comparable to conventionally fertilized embryos.

The findings support continued investigation of laboratory workflows that integrate morphological assessment with comprehensive genomic analysis to expand embryo evaluation within assisted reproductive technology research.

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