O-035 Euploidy’s hidden potential: emerging insights from abnormal fertilized embryos
Authors: Al Hashimi B , Linara-Demakakou E , Green O , Raikundalia B , Shah T , Griffin D , Ahuja K , Macklon N 
Published: July 2024

Abstract

Study question
Can pregnancies be achieved from abnormally fertilized embryos?

Summary answer
After conducting parental origin PGTA testing to confirm ploidy status, achieving pregnancy and live births becomes feasible.

What is known already
A major limitation in IVF is the availability of viable embryos per cycle. Particularly relevant for patients with poor prognosis in response to controlled ovarian stimulation. In these couples, the limited number of oocytes results in a significant reduction of the chance to achieve a live birth.
In IVF, zygotes displaying successful extrusion of the 2PB and 2PN are considered “normally fertilized” and cultured further to be used for treatment. In contrast, zygotes showing a single or more than 2PN are deemed abnormally fertilized. However, some can ultimately develop into normal embryos, which may lead to live birth.

Study design, size, duration
This is a single centre retrospective observational study of 125 blastocysts classified as abnormal through standard fertilization check post-IVF (50 embryos) and ICSI (75 embryos) Embryos were subjected to genetic testing utilizing a validated targeted next-generation sequencing-based
PGT-A protocol. The protocol's proven efficacy lies in distinguishing between haploid, diploid and triploid samples, a distinction made possible by the parallel analysis of genotyping data and chromosome copy number variations.

Participants/materials, setting, methods
The participants in this study were couples who underwent IVF cycles using PGT-A between 2021-2024. Embryos were divided into two groups based on their fertilization method
Group A involved blastocysts derived from In vitro fertilization (IVF) = 50. Classified 1PN, micro 3PN, 3PN, and 4PN. Group B blastocysts derived from Intracytoplasmic sperm injection Intracytoplasmic sperm injection (ICSI) =75 Classified 1PN, micro 3PN, 3PN, and 4PN.

Main results and the role of chance
Group A: Involved embryos resulting from IVF; 54% were diploid, with 15% being euploid from 3PN. From 1PN, 92% were diploid, and 54% were euploid. Micro PN had a 100% diploid rate, of which 33% were euploid. No diploid embryos were reported from 4PN fertilization.
Group B: Involved embryos resulting from ICSI; 36% were diploid, and 14% were euploid from 3PN. From 1PN, 53% were diploid, and 40% were euploid. Micro PN had a 100% diploid rate, with 23% being euploid. 4PN had a 50% diploid rate and no euploid embryos.
On the other hand, 0.4% (17/4822) of 2PN-classified embryos were reported as haploid, and 1.4% (68/4822) of the 2PN-classified embryos were reported as polyploid.
Eighty-nine percent of haploidy and polyploidy in ICSI originated maternally, while 71% of polyploidy in IVF originated paternally and only one embryo was haploid resulted from IVF was maternally originated.
Remarkably, three live births were reported: one from 1PN, one from Micro PN, and the third from 3PN.

Limitations, reasons for caution
The data are observational and were retrospectively analyzed, so unknown confounders could not be assessed.

Wider implications of the findings
To our knowledge, this is the most extensive cohort study analyzing embryos resulting from abnormal fertilization. It has implications for clinical practice and gives an extra chance for patients, particularly those with a low number of eggs, in response to controlled ovarian stimulation.

Trial registration number
n/a