Comment on "Reproductive Outcomes of Transferring Blastocysts Derived From Frozen-Thawed Cleavage Embryos: A...

Tran et al. synthesized seven studies (n = 2,057) comparing frozen-thawed cleavage embryos cultured to blastocyst then transferred (FT-CDB) with direct frozen-thawed blastocyst transfer (DFB) in vitrification cycles. They found higher odds of clinical pregnancy and live birth with FT-CDB and no difference in neonatal birth weight. We discuss implications for laboratories weighing thaw-and-extend versus direct blastocyst transfer, emphasizing estimands per oocyte retrieval/intention-to-treat, workflow metrics, and laboratory-level covariates. Context from randomized controlled trials (RCTs) and systematic reviews suggests cumulative live birth may converge, highlighting the need for target-trial emulation and transparent reporting to inform clinical decision-making and guideline development.