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19. 7. 2022

Embryo transfer - day 3 or day 5?


Our coordinators dedicate much time and effort to answering patients' doubts and concerns to make their journey as stress free as possible. One of the questions that often gets asked is exactly the topic of this blog article. Which is the best day for embryo transfer? Day 3 or day 5? And why? Thanks to the insights from our expert physician doctor Frgala, we will try to clarify your thoughts on this point. 

First of all, there is no absolute right answer to this question. Everything depends on patients’ individual situation. Each couple has its specific needs, and each situation deserves a tailored analysis. Both day 3 and day 5 embryo transfers are possible and both are frequently used all around the world. Many embryologists who use the time lapse techniques frequently state that on day 3 they are already able to distinguish the most favorable embryos with a good potential. However, with a larger number of embryos, many of them may be of similar quality after 3 days of cultivation. 

At Unica we generally prefer to opt for day 5 embryo transfers. This is because during the initial 3 days of development, the embryo undergoes its first division processes. At this point, the embryo’s aptitude depends mostly on oocyte quality and it is still early for the potential of the genome from both gametes (oocyte and sperm) to truly show. It is difficult to determine which ones are the most promising at this point. Simply put, it is beneficial to allow the embryos to sort themselves out, show their potential and observe which embryos are capable of forming blastocysts (day 5 of cultivation). 

Waiting for the 5th day also gives us a chance to genetically test the embryo. Through the current techniques, testing needs to be performed at a certain stage of the embryo development (expanded blastocysts, hatching blastocysts), which means it actually requires the cultivation until day five. 

Ultimately, embryo in vitro culture is a selection process. Each embryo’s progress is evaluated throughout, and a decision is taken on which one is most likely to implant successfully. At Unica, we are confident that our expert staff is in the best position to judge which embryos to select and which is the best time to transfer them. If you have more doubts on this topic, please feel free to contact our coordinators, who will be happy to answer your questions.

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