Transfers of slow-growing embryos: «fresh» day 5 morulas/early blastocysts or frozenthawed day 6 blastocysts?

Polumiskova A.O. Tevkin S.I. Shishimorova M.S. Jussubaliyeva T.M.
2022 Media Sphera Publishing Group

Russian Journal of Human Reproduction
2022 #28 Issue 5 46 - 54 pp.

Introduction. In clinical practice of assisted reproductive technologies (ART) there are cases of the entire cohort of embryos developing slowly and resulting in morulas or early blastocysts on day 5. It can be assumed that the effectiveness of slow-growing embryos transfers would be low, due to asynchrony between the development stage of an embryo and the receptivity of the endometrium. While in frozen-thawed embryo transfers with fully expanded blastocyst, the stage of embryo development and endometrium are synchronized. However, there are contradictory results reported by several studies, that compared clinical pregnancy rates (CPR) between day 5 or day 6 frozen embryo transfers (FET). Objective is to determine the best strategy of embryo transfer for patients with slow-growing embryos, to compare outcomes of day 5 morula/early blastocyst transfers in «fresh» cycles and expanded frozen-thawed blastocysts transfers on day 6. Materials and methods. The study included data of patients under 40 years old who underwent the IVF/ICSI cycles with the transfer of «fresh» embryos between 2013 and 2019, and FET between 2015 and 2019, in the Institute of Reproductive Medicine (IRM) in Almaty. The number of «fresh» cycles with the transfer of day 5 morula/early blastocyst was 436 (group A). The number of FET cycles with expanded blastocysts of day 6 (group B) and day 5 (group C, control) were 211 and 2747, respectively. Results. The CPR, the implantation rate (IR), the ongoing pregnancy rate (OPR) and the live birth rate (LBR) were significantly increased in the group B compared to the group A (CPR — 17.7 (110/619) vs 47.8% (101/211) p<0.001, IR — 12.6 (119/946) vs 35.7% (111/311) p<0.001, ORP — 11.9 (74/619) vs 37.4% (79/211) p<0.001, LBR — 10.5 (65/619) vs 35.5% (75/211) p<0.001). The miscarriage rate (MR) was significantly higher in group A than in group B: 35.3 (42/119) vs 18.9% (21/111) p=0.003. Moreover, the CPR, the OPR, the LBR and the IR were as following: 47.8 (101/211) vs 51.4% (1412/2724), 37.4 (79/211) vs 38.2% (1052/2757), 35.5 (75/211) vs 37.3% (1027/2747), and 35.7 (111/311) vs 36.5% (1586/4345), between day 6 (group B) and day 5 (group C, control) respectively. Statistical difference was not observed (p>0.05) in any indicators. Moreover, there was no significant difference in the MR between group B — 18.9 (21/111) and group C — 22.5% (358/1586). Conclusion. In ART cycles with scheduled «fresh» embryo transfer, the preference should be given to the day 5 expanded blastocysts of good/excellent quality. If the entire cohort of embryos has been developing slowly, the culture of embryos should be extended until day 6 with subsequent cryopreservation of blastocysts. All good/excellent quality frozen blastocyst should be transferred in the cryo cycles regardless of the day of cryopreservation.

blastocysts , early blastocyst , frozen-thawed embryo transfer , infertility , morula , pregnancy rate , slow-growing embryos , vitrification

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LLC «Institute of reproductive medicine», Almaty, Kazakhstan

LLC «Institute of reproductive medicine»

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