Association Between Fresh Embryo Transfers and Frozen–Thawed Embryo Transfers Regarding Live Birth Rates Among Women Undergoing Long Gonadotropin-Releasing Hormone Antagonist Protocols

Abstract

Background: The availability and use of frozen–thawed embryos after controlled ovarian hyperstimulation for assisted reproduction have increased with improvements in vitrification techniques and the rise of gonadotropin-releasing hormone (GnRH) antagonist protocols. Although evidence has shown that frozen–thawed embryo transfers (FETs) result in higher live birth rates than fresh embryo transfers, it is uncertain whether this association exists in cycles employing the GnRH antagonist protocol.Objective: To test the hypothesis that FETs are more likely to result in a live birth than fresh embryo transfers in a GnRH antagonist protocol cycle and to investigate whether frozen blastocyst transfer increases live birth rates compared to fresh blastocyst transfer.Design: A retrospective historical cohort study was conducted using data collected from the Department of Reproductive Medicine of Liuzhou Maternity and Child Healthcare Hospital for 1,437 patients who underwent the GnRH antagonist protocol between 1 January 2015, and 31 December 2020. The primary outcome was the live birth rate, which was compared between fresh embryo transfer and FET, and the secondary outcomes were clinical pregnancy rate and miscarriage rate, which were compared between the two groups. Analyses were adjusted to account for the age of the patient, number of embryo transfers, day of embryo transfer, and type of infertility.Results: Fresh embryo transfers accounted for 1,026 (71.4%) of the 1,437 patients who underwent the GnRH antagonist protocol in our analysis, while FETs accounted for 411 (28.6%). Patients with fresh and frozen–thawed embryos had comparable median body mass index (body mass index; 22.3 [IQR, 24.6–20.0] vs. 22.0 [IQR, 24.5–19.9]). There was a significant difference in the median age of the fresh embryo transfer group (34.0 [IQR, 39.0–30.0]) and the Frozen–thawed embryo transfer group (32.0 [IQR, 37.0–29.0]). Blastocysts were transferred in 14.6% of the fresh embryo transfer cycles and 45.5% of the FET cycles, whereas they account for 10.4% and 13.0% of all patients, respectively. The mean number of embryos transferred was 2 (IQR, 2.0–1.0) for the fresh embryo transfer group and 1 (IQR, 2.0–1.0) for the FET group, with a significant difference in the mean number of embryos transferred. The live birth rate after fresh embryo transfer vs. FET was 28.7% vs. 34.5% (absolute difference, 5.9%; adjusted relative risk [aRR], 1.15 [95% CI, 0.88–1.51]). The clinical pregnancy rates were 39.9% vs. 46.0%, respectively (absolute difference, 6.1%; aRR, 1.10 [95% CI, 0.85–1.43]). The miscarriage rates were 22.5% vs. 23.8%, respectively (absolute difference, 1.3%; aRR, 1.13 [95% CI, 0.75–1.70]).Conclusion: In this retrospective study of women who underwent assisted reproduction using GnRH antagonists, FETs resulted in a higher live birth rates and clinical pregnancy rates than fresh embryo transfers, which parts of these differences were attributable to embryo stage. However, the interpretation of the findings is limited by the possibility of selection and confounding biases.

Higher miscarriage rate in subfertile women with endometriosis receiving unbiopsied frozen-warmed single blastocyst transfers

“…Nowadays it is also common practice in ART clinics to transfer frozen-warmed blastocysts for different reasons: no pregnancy after fresh embryo transfer, ovarian hyperstimulation syndrome and in particular in endometriosis patients embryo transfer may be delayed due to planned endometriosis surgery before embryo transfer if persisting endometriosis symptoms are present and/or endometrioma surgery is inevitable and is potentially threatening the ovarian reserve. To our knowledge, there is a lack of reliable data on pregnancy rates after fresh vs. frozen thawed embryo transfer in endometriosis related infertility but in a retrospective study of women without endometriosis treated with an antagonist protocol live birth rates in frozen-warmed embryo transfers where shown to be higher compared with fresh embryo transfer (Fan et al, 2022), while others did not show a benefit of a freeze-all strategy in comparison with a fresh embryo transfer (Feichtinger et al, 2019;Wong et al, 2021). As frozen-thawed embryo transfer is common practice it was chosen as inclusion criteria in this study, even though further investigation on its benefit is required.…”

Effect of interval between oocyte retrieval and resuscitation embryo transfer on pregnancy outcomes

“…Although, there are some studies suggest that the administration of a rescue double GnRH antagonist dose at 1 day before hCG trigger may represent a safe alternative preventive strategy for preventing early OHSS without affecting the reproductive outcomes ( 12 ). However, more studies are pointing to embryo transfer in resuscitation cycles to improve clinical pregnancy rates and live birth rates and to reduce the occurrence of OHSS ( 13 , 14 ). There are many randomized controlled trials comparing the advantages and disadvantages of conventional whole embryo freezing and fresh cycle transfer strategies ( 15 ).…”

Improved pregnancy rate and sex ratio in fresh/frozen in vivo derived embryo transfer of Hanwoo (Bos taurus coreanae) cows

“…These results are consistent with those of Ferraz et al [ 24 ] who demonstrated a higher pregnancy rate with fresh embryos than with frozen embryos. This suggests that freezing affects the pregnancy rate of IVD embryos [ 25 ]. However, the present study revealed that frozen embryos transferred using the current freezing protocol exhibited pregnancy rates similar to fresh embryos.…”