Answer from: Luboš Vlček, MD
Natural embryo selection is helping us to transfer healthy embryos. That’s why we are usually waiting till day 5. This is the prevention against the repeated Ds; Cs because of miscarriages. But, I think in the individual cases, if you do not have the option to make a selection or choice for more embryos, it is better to transfer them on day 3, rather than waiting today 5.
Answer from: Ruth Sánchez, MD
The implantation rate is better on day 5 so we always prefer it for transferring blastocysts. There are several reasons for this. First, it helps to make a better selection of the embryos to be transferred and to be frozen since we have more information about the genetics, morphology, synchrony of the cells and so on.
Second, it allows greater synchronicity with the endometrium preparation—more days of progesterone, less contractual activity of the uterus since the progesterone acts as a uterine relaxant. Third, it allows a preimplantation genetic study to be made to select euploid embryos.
Answer from: Roksolana Semchyshyn, MD, PhD
We can have two options: day 3 embryo transfer and day 5 embryo transfer. At Intersono IVF clinic, we have a higher clinical pregnancy rate when we are doing the embryo transfer on day 5.
Why? We have several reasons for that.
First, this is Mother Nature. During natural conception, the embryo drops into the uterus on day 5. So it is a natural situation when a day 5 embryo is in our uterus. During natural conception, the embryo is in the tubes. So it is not a natural situation when a day 3 embryo drops into our uterus. Therefore, higher clinical pregnancy results are on day 5 embryo transfers.
The second reason is the option for selection. It is the oocyte that is responsible for the first 3 days of embryo development. The sperm is responsible for the next two days. In that case, when we have a sperm factor, sometimes we can have the good embryo on day 3, but we don’t have the blastocyst stage on day 5. Therefore, if you transfer a day 5 embryo, we have the option of selecting, and we can choose the best embryo.
The third reason is the opportunity to do PGS screening of the embryo. When we’re talking about a day 3 embryo, at that stage, the embryo consists of cells. It is an ideal situation when we have 8 cells. When we are doing the biopsy on these embryos, we’re taking out just 1 or 2 cells. In that case, when we are doing the biopsy on those embryos, we can miss some pathology. For example, in one cell, we can have a normal chromosomal structure, and the other can contain the abnormal chromosomal structure.
When we are doing the biopsy on day 5 embryos, we don’t have separate cells. In that case, all cells are equal, and we can’t miss the mosaic embryo. Intersono IVF clinic recommends you to do embryo transfer on day 5 to get higher chances for pregnancy.
Answer from: Zane Vitina, MD
When the embryo develops till the 5th day after fertilization naturally, it is situated in fallopian tubes. At the end of the fifth or sixth day, it exceeds the uterus and is ready to implant.
The 3-day embryo is called the cleavage stage and consists of 8 cells, while the day-5 embryo already consists of approximately 100 cells. There is a natural selection between 3-day and 5- day embryo. If we compare the number of good quality embryos on 3-day and 5-day, it differs. It has been proved that the total pregnancy count of one stimulation is the same.
The only difference is the number of embryo transfers, and it’s easier for women to undergo fewer embryo transfers than more to achieve their goal, a baby.
Answer from: Buse Karanlık
First of all, day 3 is the intermediate stage of embryo development. Day 5, the blastocyst stage, is the final stage of embryo development when we finally understand if we have a good quality or a bad quality embryo. We can have the situation when on day 3, we have a bad quality embryo, but on day 5, we receive a blastocyst of intermediate or even good quality.
We can also have the opposite situation. On day 3, we can have a very good quality embryo, but after day 4, a sperm factor can influence the embryo quality, and we will not receive a blastocyst-stage embryo on day 5.
Answer from: Aldo Isaac Meneses Rios, MD
The implantation rate is better on Day 5, so we always prefer it for transferring blastocysts. There are several reasons for this. First, it helps to make a better selection of the embryos to transfer and to freeze because it’s a more morphological stage when the embryo is attached across the endometrium during natural conception.
Another advantage is that we have more information about the genetics, morphology, synchrony of the cells, and the cleavage process. It allows greater synchronicity with the endometrium preparation. We can use more days of progesterone to have a less contractive activity of the uterus since the progesterone acts as a uterine relaxant. It allows us to make a preimplantation genetic study to select euploid embryos in the fresh cycle without the need to freeze and refer the eggs for transfer. The culture of these low-quality embryos to the blastocyst stage allows us to recover and freeze some embryos that would have otherwise been discarded. This action helps us to distinguish between viable embryos with the greatest potential for replantation.
There is no consensus on deciding the fate of poor-quality embryos on day 3. The transfer of these embryos is highly inefficient due to their low implantation rates. However, by discarding the embryos, we risk losing embryos that might be implanted. The culture to blastocyst stage is an additional opportunity to assess whether it’s worth cryopreserving them. The best option to do this is to individualize the day of the embryo transfer according to both the maternal age and the number of available embryos on day 3 to decide if it is possible to carry it out on day 5 if the previous embryo transfer was unsuccessful on day 3.
Answer from: Robert Najdecki, MD, PhD
The topic of our podcast, “Day 3 vs. Day 5 embryo transfer”, is still a controversial issue with no common consensus yet reached. Early studies have failed to show a significant difference between day 3 ET and day 5 ET, where hCG levels, clinical pregnancy, implantation, and early pregnancy loss are concerned, resulting in an individualized specialist approach.
But first, let’s just go back to the basics and review the sequence of events taking place after ovulation. On day 14 of a 28-day cycle, the oocyte (egg) is released by the ovary and picked up by the fimbriae (finger-like projections) of the fallopian tube. The egg is moved along passively by the ciliated endothelial cells of the fallopian tubes towards the uterus. If on its way, it is met and fertilized by sperm, it becomes a zygote, the very first cell of the whole new organism consisting of the combined maternal and paternal genome.
Following a series of identical mitotic divisions, the embryo’s growth results solely from the oocyte’s potential to become a mass of 6-8 undifferentiated cells by day 3. After the embryo’s own genomic activation, this mass of cells develops into the blastocyst.
By day 5, the blastocyst has a fluid-filled cavity surrounded by a layer of differentiated trophoblastic cells, which will form the placenta, and an inner cell mass, which will eventually become the fetus. By day 5, the blastocyst has entered the uterine cavity, and in the next day or so, it will hopefully manage to hatch out of its prospective protein coat, the Zona Pellucida, and successfully implant into the receptive endometrium.
During IVF, the oocytes are picked up by ultrasound-guided transvaginal aspiration on the designated day. They are appropriately prepped, evaluated, and fertilized in the lab. The embryos produced are put under close supervision and strict lab conditions in specially designed cultivation media and incubators. The latter, so-called Time-Lapse incubators, allow their 24-hour observation. All developing embryos seem to pause on day 3 and day 5, allowing us to evaluate their dynamic state and select the best looking ones based on specific morphological criteria for transfer into the uterine cavity. This is done via the cervical canal and onto the well-prepped, by progesterone, the endometrium.
Some IVF specialists argue that day 3 embryo transfer is preferable in older patients and poor-responders, with a low number of good quality embryos. In this instance, day 3 embryo transfer is less expensive with a low risk of losing good embryos by culture and can potentially yield better cumulative pregnancy rates as studies have shown that even borderline quality embryos transferred on day 3 may potentially lead to pregnancy, compared to no embryos transferred.
Nowadays, however, and in clinics such as ours, with extensive experience in the cultivation process and excellent blastocyst survival, following the vitrification process, day 5 embryo transfer makes much more sense, even in poor responders. In labs, when the blastulation rate index is over 60%, and the possibility of achieving the blastocyst stage is high, day 5 embryo transfer is favoured. Allowing the embryo to reach the blastocyst stage allows us to make an educated guess on the embryos that have the highest potential to survive and successfully implant. Thus avoiding futile attempts of transferring day 3 embryos destined to arrest and reducing the time needed to achieve a successful pregnancy. Additionally, day 5 embryo transfer offers patients more transparency, giving them a clear view of the available embryos, which are of the best quality since they survived and grew through the biologically selective process. But, what if the embryos which are available on day 3 are of very poor quality? Is it a good idea to carry out the embryo transfer on day 3, rather than wait until day 5? In the group of fresh-cycle, followed by fresh embryo transfer, day 3 transfer is an acceptable decision. For us, it is accompanied by a detailed discussion about the expected implantation success rates. However, in the case of frozen-cycles, which nowadays account for more than 70% of all cycles, day 5 transfer is the preferred approach to ensure that only the best quality embryos will be vitrified, thus yielding a better pregnancy rate or subsequent transfers.
Lastly, day 5 embryo transfer reduces biopsy embryo loss rates. Performing a trophectoderm biopsy during PGT (prenatal genetic testing) on day 5 allows us to extract more cells, consequently improving the accuracy of the genetic diagnosis with a concomitant lower risk of embryo viability, compared to whole blastomere extraction during day 3 biopsy. From our own experience, day 5 ET has higher clinical pregnancy and live birth rates compared to day 3, especially with fresh-cycle.
In summary, day 5 embryo transfer is shown to be more transparent for the patients and reproductive scientists, giving them a clear view, as it acts as a biological filter on embryo quality. In the era of total freezing strategy, which includes 70% of all performed cycles, day 5 frozen embryo transfer shows higher percentages of clinical pregnancy, reaching up to 50%. In our lab, the survival rate after blastocyst thawing is over 95% and strongly supports the use of frozen blastocysts. Day 5 blastocyst embryo stage makes it easy to use the NGS (next-generation techniques) during prenatal genetic testing, which is shown to be the new trend in reproductive medicine. By transferring the euploid blastocyst, we achieve over 60% in the clinical pregnancy rate.
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Is day-3 embryo better for the transfer than day-5?
Embryo development is a complex topic – one which has far-reaching consequences on the entire process of pregnancy. Embryo quality, after all, is one of the deciding factors in embryo implantation. Only by closely observing the development process can we determine which embryos are healthy enough to be transferred and which ones won’t result in a successful pregnancy.
The day at which the embryo is transferred is also a significant factor in the entire IVF process. Two main points of embryo development have been pinpointed as the best time to transfer: day 3 and day 5. Is one option better than the other?
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