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First of all, it is known that, embryo morphology correlates with successful implantation (Farhi, et al., 2001). Embryologists and clinicians are uncomfortable when faced with decisions involving ongoing culture of poor-quality, day-3 embryos, as the true potential of a low-scoring embryo to yield a viable fetus is uncertain. This question is even more troubling when a given cycle yields only poor grade embryos. On the other hand, discarding an embryo, which has potential for future pregnancy, is certainly undesirable (Balaban, et al., 2001).
Sometimes an embryo with a high score fails to implant, as may an unfavorable embryo result in a viable pregnancy. Normally around 25 % of the embryos are lucky enough to go day 5 , basically this is kind of embryos `natural selection`. Day 3 embryos have a higher aneuploidy rate so some may drop out, or arrest/stop growing, by going to Day 5.The ones that can go to day 5 means that they are good enough to make the blastocyst. The selection provided by blastocyst culture seems to be always safer.
Recent researches, showed that low scoring day-3 embryos that are not considered transferable can still result in successful blastulation and a live birth. This is really a very important point for reproduction specialists and for concerned patients (Balaban, et al., 2001).
Secondly, there is an another important parameter that supports idea of culturing poor quality of day 3 embryos to day 5. It is thought that the uterine environment, at least in theory, may not be a better environment for a Day 3 embryo.That’s because it takes about 4 days for the embryo to make it to the uterus. On Day 3, the embryo is still making its way through the Fallopian tube so this environment may be better suited (Glujovsky & Farquhar, 2016)
By Day 5, the embryo is in the uterus. And this synchronization between embryo and the uterus may be an important factor for success. Some believe that Day 3 embryos may experience stress in this environment (Glujovsky & Farquhar, 2016). More research needs to be done on this topic as this will require a bunch of research in how embryo culture compares to the natural environment. But for now, at least appreciate that some don’t think the uterine environment is ideal for a Day 3 embryo. Transfer at this stage is considered to be a more physiologically appropriate time as it more closely mimics the time of natural implantation and may improve synchrony between the endometrium and embryo development (Glujovsky & Farquhar, 2016).
In conclusion, because of these reasons mentioned above, if embryos are available on Day 3 are very poor quality, I would suggest to wait until day 5 to select best transferable embryos with better synchronization between embryo and the uterus on day 5. Otherwise, there is a potential risks of discarding an embryo which might provide a successful live, transferable embryo on day 5.
26 авг 2024
