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Updated: Sep 23, 2025
Morphometric Protocol for the Objective Assessment of Blastocyst Behavior During Vitrification and Warming Steps
Published on: February 28, 2019
A comparison of frozen-thawed embryo transfer protocols in 2920 single-blastocyst transfers
Einav Kadour-Peero1, Ido Feferkorn2, Veronique Bellemare2
1Department of Obstetrics and Gynecology, Division of Reproductive Endocrinology and Infertility, McGill University, Montreal, QC, Canada. einavkadour@gmail.com.
Objective:
To assess the effect of frozen-thawed embryo transfer (FET) protocol on live-birth rate (LBR) and clinical pregnancy rate (CPR), in single-vitrified-blastocyst transfer MATERIALS AND METHODS: Retrospective cohort study with FET of a single-blastocyst embryos (n = 2920 cycles) thawed 2013-2018. FET protocols were natural cycles (NC-FET) (n = 147), artificial hormone replacement treatment cycles (HRT-FET) (n = 2645), and modified NC (mNC) with hCG triggering (n = 128). Primary outcome was LBR. Adjustment for age, embryo grade, year of freezing\thawing, infertility cause, and endometrial thickness was performed.
Results:
There were no significant differences between the groups with regard to female age, embryo grade, and endometrial thickness. LBR was higher in the mNC compared to HRT-FET cycles (38.3% vs. 20.9% P < 0.0001), and in the NC compared to HRT-FET cycles (34.7% vs. 20.9%, P = 0.0002). CPR was higher in the mNC compared to HRT-FET cycles (46.1% vs. 33.3% P = 0.0003), and in the NC compared to HRT-FET cycles (45.9% vs. 33.3%, P = 0.002). There was no significant difference in LBR or CPR between NC-FET and mNC-FET. Higher LBR with NC-FET and mNC-FET remained significant after adjusting for confounders (aOR 2.42, 95%CI 1.53-3.66, P < 0.0001).
Conclusion:
The use of the convenient artificial HRT-FET cycles must be cautiously reconsidered in light of the potential negative effect on LBR when compared with natural cycle FET.
