Thawing day 3 embryos and culturing to day 5 may be a better method for frozen embryo transfer

Roni Rahav-Koren*, Shmuel Inbar, Netanella Miller, Amir Wiser, Yael Yagur, Chen Berkowitz, Sivan Farladansky-Gershnabel, Adrian Shulman, Arie Berkowitz

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Purpose: Does thawing cleavage embryos and culturing them for transfer as blastocysts improve pregnancy and perinatal outcomes compared to transferring thawed blastocysts? Methods: Retrospective, observational cohort study performed at two assisted reproductive technology centers, 2014 to 2020. A total of 450 patients with 463 thawed embryo transfer cycles were divided into 2 groups according to the embryonic developmental stage at cryopreservation and transfer: 231 thawed blastocysts (day 5 group) and 232 thawed cleavage embryos that were cultured for 2 days and transferred as blastocysts (day 3–5 group). The two groups were compared for demographics, routine parameters of IVF treatment, pregnancy rates, and perinatal outcomes. Results: Multivariable logistic regression analysis for ongoing pregnancy and delivery demonstrated that the day 3–5 group had a greater likelihood of achieving ongoing pregnancy and delivery compared to the day 5 group (OR 1.58, 95%CI 1.062–2.361, p = 0.024). Perinatal outcomes were comparable between the three groups. Conclusion: Our results support culturing post-thaw cleavage embryos for 2 days and transferring them as blastocysts to increase chances of ongoing pregnancy and delivery.

Original languageEnglish
Pages (from-to)2941-2946
Number of pages6
JournalJournal of Assisted Reproduction and Genetics
Issue number11
StatePublished - Nov 2021


  • Blastocyst
  • Cleavage
  • Thawed embryo transfer
  • Vitrification


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