To discard or to not discard 2.1PN? A systematic review and evidence table analysis

To assess if 2.1PN-derived embryos are diploid, euploid and suitable for embryo-transfer.

This systematic review was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. PubMed, Embase, and SCOPUS were systematically searched for peer-reviewed original papers using relevant keywords and Medical Subject Heading (MeSH) terms. Diploidy, confirmed by genotyping analysis, is defined as the primary outcome measure. Secondary outcomes included blastulation rates, good quality blastocysts, euploidy, clinical pregnancy, miscarriage and live birth (LB).

A total of 7 studies were included in the systematic review. Six out of seven studies indicated that 2.1PN embryos have lower developmental competence than 2PN embryos, yet can still be euploid/diploid. Only one study advised against their use for embryo transfer. In our analysis of the evidence tables, 2.1PN-derived embryos showed a descriptive trend toward lower blastulation rates (- 22.50%), good-quality blastocyst formation (- 12.93%), diploidy (- 16.70%), and euploidy rates (- 28.37%) when compared with their 2PN counterparts. Four studies also analyzed LB in 2.1PN, reporting an overall LB of 30.4% (7/23). Finally, based on the crude aggregated blastulation (32.30%), euploidy (35.0%), and diploidy (82.0%) rates, the estimated probability for a single 2.1PN zygote to develop into a euploid and diploid blastocyst was 9.3%.

Although 2.1PN-derived embryos exhibited lower developmental competence, they showed potential for healthy LB. Our findings support the clinical use of 2.1PN-derived embryos when diploidy is confirmed by a validated genotyping analysis, providing further empirical evidence to support more inclusive and flexible clinical recommendations, potentially improving cumulative success rates.

CRD420251070366.