Document Type

Journal Article




Faculty of Computing, Health and Science


School of Medical Sciences




Liu, Y., Peirce, K., Yap, K., McKenzie, K., Natalwala, J., Chapple, V., Norman, M., & Matson, P. L. (2012). The fate of frozen human embryos when transferred either on the day ofthawing or after overnight culture. Asian Pacific Journal of Reproduction, 1(3), 187-192. Available here


Objective: To study the performance of thawed zygotes and cleavage stage embryos transferred either on the day of thaw or after overnight culture. Methods: A retrospective study of 864 frozen embryo transfer cycles. Cryosurvival rates per thawed embryo and implantation rates were analysed for embryos frozen on Day 1, Day 2 or Day 3 relative to oocyte collection (Day 0) and transferred on the day of thaw or after overnight culture, together with clinical pregnancy rates and prevalence of multiple gestations. Results: Survival of Day 3 embryos was significantly lower than those frozen on Day 1 (P=0.017) or Day 2 (P=0.015). Following overnight culture, resumption of mitosis of zygotes was more frequent than Day 2 (P=0.000) which are in turn higher than Day 3 (P=0.000) embryos. The implantation rate for Day 2 embryos dividing overnight was significantly higher than those that did not divide for women (P=0.001) but not those women (P=0.055). There were no differences in the implantation rates for those dividing or not after culture, for embryos frozen on Day 3 for women (P=0.254) or (P=0.403). Conclusions: Later cleavage stage post-thaw embryos survive and resume mitosis less frequently compared to earlier stages. Embryos not resuming mitosis after culture overnight can implant, particularly Day 3 embryos, suggesting that they can further increase the cumulative pregnancy rate per oocyte collection and that discarding them is wasteful. Overnight culture is best used for logistical reasons rather than a strategy to improve pregnancy rates.



Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.