Establishment of day 7 blastocyst freezing criteria using blastocyst diameter for single vitrified-warmed blastocyst tra
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ASSISTED REPRODUCTION TECHNOLOGIES
Establishment of day 7 blastocyst freezing criteria using blastocyst diameter for single vitrified-warmed blastocyst transfer from live birth outcomes: a single-center, large cohort, retrospectively matched study Satoshi Ueno 1 & Kazuo Uchiyama 1 & Tomoko Kuroda 1 & Tadashi Okimura 1 & Akiko Yabuuchi 1 & Tamotsu Kobayashi 1 & Keiichi Kato 1 Received: 21 December 2019 / Accepted: 6 July 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Purpose To establish blastocyst freezing criteria for day 7 blastocyst (day 7 BL) for single vitrified-warmed blastocyst transfer (SVBT) by examining the diameter of blastocysts. Methods Patients who underwent day 7 BL transfer cycles (1143 cycles, mean age: 38.5 ± 3.5) and randomly selected patients after 1:1 matching who underwent day 6 BL transfer cycles and day 2-single-embryo transfer (SET) cycles were used for analysis. Comparison of the miscarriage (per clinical pregnancy) and live birth rates were made among day 2-SET, day 7 BL, and day 6 BL. These blastocyst groups were stratified into six groups based on blastocyst diameter, namely, 180 μm, 190 μm, 200 μm, 210 μm, over 220 μm, and hatched, for making the freezing criteria. Results For each diameter, 180 μm, 190 μm, 200 μm, 210 μm, over 220 μm, and hatched, the live birth rates of day 7 BL after SVBT were 9.0%, 11.9%, 11.5%, 15.6%, 20.0%, and 19.9%, respectively. Compared with the 14.6% live birth rate of the day 2SET group, the live birth rate of 220 μm day 7 BL was significantly higher (P < 0.05) and was around the same in other diameter groups. Conclusion Our study demonstrates that sufficient live birth rates can be obtained after SVBT even from blastocysts on day 7 when blastocysts were vitrified at expanded blastocyst stage of over 180 μm of diameter or at hatched blastocyst stage and were transferred at the optimal time. This is the first study to establish a day 7 blastocyst freezing criteria using blastocyst diameter, which is an objective assessment way. Keywords Blastocyst diameter . Blastocyst freezing . Day 7 blastocyst . In vitro fertilization . Single vitrified-warmed blastocyst transfer
Introduction There are some benefits associated with vitrified-warmed blastocyst (BL) transfer. It makes it possible to select embryos with a high implantation ability by culturing BLs and cryopreserving them once so that the uterine environment is suitable for implantation [1, 2].
* Keiichi Kato [email protected] 1
Kato Ladies Clinic, 7-20-3, Nishi-Shinjuku, Shinjuku, Tokyo 160-0023, Japan
Generally, it is rare for a BL to be used for a transfer on its seventh day after fertilization. Studies on day 7 BL usefulness and their clinical outcomes have indicated that pregnancy rates were low compared with those of day 5 and day 6 BLs. One study suggested that day 7 BLs should not be used for in vitro fertilization (IVF) treatment if the BL has not hatched by day 7 [3]. However, several studies suggested that day 7 BL transfer results in pregnancy rates that a
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