IS IT WORTH TO WAIT THAWED BLASTOCYTES FOR MORE THAN 4 HOURS TO EXPAND IN FROZEN-THAWED IVF CYCLES ?

• Published in: Reproductive biomedicine online 2024-11, Vol.49, p.104572, Article 104572
• Main Authors: Aytac, Pinar Caglar, Alkas, Didem, Durdag, Gülsen, Yetkinel, Selcuk, Simsek, Erhan
• Format: Article
• Language: English
• Subjects: blastocyte; expansion time; frozen-thawed cycle,ivf
• ISSN: 1472-6483
• DOI: 10.1016/j.rbmo.2024.104572

We aimed to compare the pregnancy outcomes of thawed blastocytes who expanded before and after 3- 4 hours before intra uterine transfer in FET (Frozen embryo transfer) cycles. In a IVF Unit of University Hospital, between January 2022 and January 2023, all FET (frozen embryo transfer) cycles were included. It is an observational, cross sectional prospective study. During one year, after blastocytes were thawed, they followed for expansion all the day before intra uterine transfer. Embryos which were checked for expansion after thawing on second and fourth hours. If they expanded properly there were transferred. But if not, they were going to be checked every two hours up to maximum 8 hours after warming of them. The FET cycles which embryos which expanded after 4 -8 hours were grouped 1. The FET cycles which embryos expanded first 3-4 hours were group 2. These two groups were compared according to pregnancy rates and live birth rates which are our primary outcome. Secondary outcomes were implantation rates and miscarriage rates. In group 1 there was 66 number of FET cycles, in group 2 there were 218 number of FET cycles. The pregnancy rates were 43.9% and 65.6% in group1 and group2 in orderly (p:0.001). Live birth rates were 28.8% and 35.3% in group 1 and 2 in orderly (p:0.20). Implantation rates were 31.7 % and 51.2 % in group1 and 2 (p:0.03) and miscarriage rates 11.1% and 23% in orderly (p:0.34). Even expansion time is a prognostic factor in the determination of viability of thawed blastocytes in FET cycles, live birth rates may be not decreased as expected. So waiting up to 8 hours for expansion of embryos may be preferable option instead of abandon embryos that not expand after two hours. But it is not known what is the upper limit for time to wait these embryos, there is still no clear cut off time to stop follow up for these non expanded embryos.