Day three VS day five embryo transfers
The decision of transferring the embryos on the 3rd or 5th day requires heedful reasoning and contemplation. Generally, embryos have a better chance of successful implantation after they form blastocysts. Sadly, all embryos do not progress to reach the stage of blastocyst outside of the body. This fact raises the question of whether the embryos that could not form a blastocyst could have been able to have initiated a pregnancy in case those had been transferred into the uterus on the 3rd day.
Various researchers have demonstrated acceptable rates of pregnancy with day-3 embryos transfers of marginal quality would have been less likely to form blastocysts in culture. Distinctly, the pregnancy rate during the absence of an embryo transfer will be equal to zero. On the other hand, embryos of even marginal quality may potentially lead to a pregnancy when transferred on day-3. Besides, when normal fertilization is followed inside the fallopian tube, the embryo does not appear into the uterus before day-5 after the ovulation. There is improved synchronization between the endometrial lining and the embryo as the embryo transfer is executed on day 5. It possibly leads to increased rate of implantation.
IVF Success Rates with Blastocyst Transfer
Success rates of day 5 blastocyst transfer are potentially confusing. Almost every fertility clinics that are in favor of extended blastocyst transfer IVF and embryo culture are critical in selecting patient’s eligibility for it.
Patients going for blastocyst transfer are much younger in age and have more developed and better quality embryos to study prominently under the microscope. Hence, the success rate is higher in the selected couples rather than for the bulks going for it.
Number of Eggs Retrieved and IVF Success
So, it is an important question to decide between a day-3 and a day-5 embryo transfer. Some fertility clinics decide on day 3. If a patient has a specific number of high-quality embryos developed within day 3, the embryos are continued to be cultured for 2 more days to facilitate selection from more embryos at the time of transfer. If the embryos cannot develop to the stage of blastocyst stage, no transfer can be done as it would certainly result in profound patient disappointment. In case a limited number of embryos are obtained on day 3, those can be transferred on the very same day without any embryo selection. This is because in such cases the benefits of a day-5 embryo transfer remain limited.
We, at our fertility treatment unit have become more convinced of the benefit that can be obtained from extended embryo culture. On the 3rd day, which is also popularly sometimes called as the marginal-appearing day, the embryos are found to be developed into beautiful blastocysts and engender successful pregnancy and delivery. A few top grade 8-cell embryos sometimes fail to multiply itself within 3 days, and hence, results in a canceled embryo transfer. The patients who fails to sometimes conceive with high-quality day-3 embryo have to subsequently wait to be conceived with a day-5 transfer.
There remains an additional risk of increased rate of identical twinning in a day-5 transfer. The risk of carrying identical twins or monozygotic twins is found to be a higher in such pregnancies than carrying fraternal twins or dizygotic twins. Identical twins mostly share the same placenta and are known as monochorionic twins. They can be located inside the same pregnancy sac and are called monoamniotic twins. These two conditions are associated with the enhanced pregnancy complications.
Also, the success of a fertility clinic with embryo cryopreservation after an extended culture has to be carefully considered. Recent advancements in the field of rapid freezing (vitrification) have caused excellent survival rates and have enhanced the pregnancy rates with the introduction of blastocysts. Extended culture should be carried out with cryopreservation program to maximize patient success.
Embryo Transfer on Day 3 or Day 5
Deciding on the ideal day of embryo transfer is still a matter of controversy. It actually does not have a definite time frame and can be altered based on each situation.
Embryo culture is actually a selection process. The progress of every embryo is thoroughly evaluated and a final decision is made on which day is most likely to have a successful implant.
The decision is made on the clear evidence of embryo development in the preserved stage. Every embryo gets multiplied on day 2 or day 3. If the embryo is found to be successfully divided itself and formed a healthy blastocyst in day 3, many embryologists prefer to transfer it on the same day. If not, they wait for another 2 days to allow the embryo to completely develop itself into a healthy blastocyst and then the selection process is carried out, followed by the transfer.
The greatest fear is whether extending embryo culture can stop the development of the embryos because they’re not in the uterus. This actually depends on the IVF laboratory. The extensive experience gained from the prolonged cultivation processes help to gain accuracy in this field. There is no set rule or even a thumb rule for this. The entire process is based on the embryologist’s observation and determination. No fertility clinic follows any standard rule for the embryo transfer or extended culture. The motive is to transfer the embryo when it reaches the ultimate development stage to create form a healthy pregnancy.
There are various benefits related to embryo selection and transfer on day 3 or 5, which are embryo-endometrial synchrony. The endometrial window for embryo implanting is actually limited. Once the embryo development and endometrial receptivity are closed together, the embryologist can increase embryo implantation rates and successful pregnancy initiation.
There is one more fear associated with the survival of blastocysts during freezing. Vitrification method of freezing has unfounded this fear and the survival rate of blastocyst has reached 95%.
Every fertility clinic puts emphasis on the fact that no risk should be rendered on the viability of the embryos. No extension is ever supported where the life or development of the embryos are at risk.
It can be concluded that embryo culture until day 5 is considered to be a complex process but helps immensely in improved selection of embryos in particular cases. Transfer of embryos on the 5th day minimizes the number of embryos to be transferred, and, thus, twin pregnancies can be achieved. It also gathers good results throughout the pregnancy. However, many cases of embryo transfer are recorded to be carried out on day 3 as the developed embryos do not require additional embryo selection.
So, both the policies are used by most fertility clinics to perform the job successfully. The primary objective of IVF treatment is to initiate a healthy pregnancy. Many trial and errors are conducted in this procedure to increase the chances of healthy pregnancy and delivery. The same is with the embryo transfer. Instead of being imprisoned in a rigid policy, maximum embryologists consider the condition of the embryo to transfer it for a successful pregnancy and delivery.