A comparison of frozen-thawed embryo transfer protocols in 2920 single-blastocyst transfers.

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.