ESHRE 2021

Coffee-break discussion: Should we transfer embryos derived from 0PN and 1PN oocytes?

Published 07 July 2021

Consensus from a lively coffee-break at the Annual Meeting concluded that abnormally fertilized oocytes can be rescued for clinical use and result in healthy live births. Efthymia Constantinou, Junior Deputy from the SIG Reproductive Genetics, reports.

At a well attended coffee-break discussion on the transferability of embryos derived from abnormally fertilised oocytes (AFO), Drs Catello Scarica and Antonio Capalbo, incoming co-ordinator of the SIG Reproductive Genetics, emphasised that AFO can be rescued for clinical use and result in healthy live births.

Capalbo showed evidence highlighting that testing for ploidy is fundamental; 0.5-1% of blastocysts from 2PN zygotes have ploidy abnormalities, 50% of blastocysts derived from 1PN are normal diploid, and 10-20% of 3PN derived blastocysts are normal diploid. Indeed, healthy live births have been reported with AFO following ploidy analysis by specific protocols. Capalbo illustrated, however, the potential for impaired development of AFOs, the majority of which failed to reach the blastocyst stage. Out of 719 PGT-A cycles examined, in 3.6% at least one AFO blastocyst was derived - and just 0.4% were derived from AFO-only.
Embryologist Scarica, IVF laboratory director at the European Hospital Rome, primarily referred to the prevalence of 0PN zygotes (10-20%) and 1PN zygotes (5-9%) after IVF or ICSI. In agreement with Capalbo, he also presented evidence that 0PN resulted in 15-26% live births. Once again, the usefulness of euploid-diploid discrimination through genetic testing was demonstrated by various studies. A recent study, however, raised by Scarica and referring to the postnatal outcomes of embryos derived from 0PN, concluded that 0PN-derived singletons had a higher birthweight than those from 2PN-derived embryos.

Capalbo and Scarica both stressed the emerging need for updated international guidelines on the subject. More specifically, Capalbo referred to the guidelines of ESHRE (2015) and ASRM (2017), with Scarica adding the recent consensus of the Italian Society of Embryology and Italian Society of Human Genetics.

To sum up, Capalbo and Scarica agreed the following:
1. An update of international guidelines is essential
2. Investigation of ploidy status is fundamental
3. 2PN-derived embryos should prioritised for embryo transfer
4. ≥3PN derived embryos should never be considered for transfer
5. prolonged culture to blastocyst stage for 0PN and 1PN derived embryos is strongly encouraged
6. Genetic counselling is mandatory

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