Embryo transfer in the process of test tube surrogacy in the United States is a very important step. Many prospective parents are faced with a problem, whether to choose a 3-day embryo or a 5-day blastocyst transfer? Today we take a look at the difference between the two.

In the past, clinics could only transfer embryos that had been cultured for 1-3 days. These embryos were called "cleft stage" embryos.

With the rapid development of assisted reproductive technology and laboratory equipment, clinics can now culture embryos to 5-6 days of blastocysts before completing the most important embryo transfer surgery.

The current IVF cycle, blastocyst culture and single blastocyst transplantation have received increasing attention. In particular, guests who know something in the early stage often think that the success rate of blastocyst transfer will be higher than that of embryo transfer in cleavage stage.

Is blastocyst transplantation suitable for everyone?

First of all, we must know that blastocyst transfer is a type of IVF embryo transplantation, which can improve the implantation rate of IVF embryos while reducing the possibility of multiple pregnancy.

After fertilization, the egg will rapidly divide and proliferate, and the fertilized egg will grow to the cleavage stage on the third day, at which time the embryo develops to a stage with 3 cells inside.

And on the fourth day, the embryo will undergo an important metabolic transition and develop into the mulberry embryo stage.

And on the fifth day the embryo will develop into a blastocyst, which is called the blastocyst stage, and the embryo has formedNourish ectoderm, inner cell mass and blastocyst, The embryo already contains more than one hundred cells,

Nourishing the outer layer will form the umbilical cord, placenta and membrane, while the inner cell mass will develop into a fetus.

Many guests are not clear about the difference between blastocyst transfer and universal embryo transfer:

Test tube baby blastocyst transfer technology is to imitate the law of natural pregnancy. When the embryo develops into a blastocyst state, the blastocyst embryo is transferred into the mother's uterus, which can increase the success rate of test tube baby and reduce complications.The success rate of test-tube baby blastocyst transplantation is significantly higher than that of ordinary transplantation by about 20%.

Generally speaking, only good quality embryos can eventually form blastocysts. Therefore, we believe that for the embryo, the growth potential is more reflected in the blastocyst stage.

What is the difference between cleavage stage embryo and blastocyst?

No.1 Different cultivation time

Cleavage stage embryos refer to embryos developed to day 3, and blastocysts refer to embryos developed to days 5-7.The final stage of embryo development in vitro.

No.2 Different development potential

Blastocyst transfer makes embryo transfer selective.

useFresh embryo(8-cell stage) morphology to measure embryonicDevelopmental potentialThere are certain restrictions on the transfer of embryos of this period, itsLater development potential is still difficult to predict. Blastocysts are cultured in vitro for 2-3 days longer than cleavage stage embryos. Embryos that can develop into blastocysts show that they have excellent genes and the ability to adapt to the external environment, and the overall quality is also better. During the cultivation process, natural selection for survival of the fittest, abnormal chromosomes or genes, and embryos with insufficient genes and poor development potential will be eliminated. If the embryo can pass the 8-cell stage of developmental arrest and becomeBlastocyst, Then we thinkMore viable embryos.

Therefore, the blastocysts are all "excellent among the best".

No.3 The implantation rate and pregnancy rate are different

Under normal physiological conditions, the embryo in the cleavage stage is still in the fallopian tube. After transplantation, it means that it enters the maternal uterus prematurely, so it needs to be free in the uterine cavity for a few days to implant into the endometrium. Doctors usually choose 2 embryos for transplantation, which also increases the chance of multiple pregnancy.

The blastocyst transplantation is more in line with the physiological implantation time of natural pregnancy.After selecting the blastocyst for transplantation into the body, the time for the embryo to continue to develop in the uterus is shortened. The implantation of the blastocyst can be synchronized with the endometrium, which can improve the clinical pregnancy rate and embryo implantation rate, so its success rate will be relatively Higher.

In the case of high-quality blastocysts, only a single blastocyst can be transplanted to reduce the rate of multiple pregnancy.

In general, blastocyst transfer technology can identify the quality of embryos more intuitively and reliably, and this process can eliminate inferior or even defective embryos.

Recently, two large sample studies gave us some references:

One of the studies pointed out that in the fresh embryo transfer cycle, the embryos on day 3 compared with the blastocysts on days 5-6 found that the live birth rate of fresh blastocysts was higher.

该实验的数据表明，新鲜分裂期（第3天）胚胎移植的活产率为29%，囊胚移植（5-6天）的活产率为32%-42%。（*活产率即：宝宝顺利生产的概率）

The results of another study are: If the cumulative success rate of the fresh transfer cycle and the frozen transfer cycle is compared, it is found that the success rate of embryo transfer (day 3) is 49%, and the success rate of blastocyst transfer 52%.

We found that usually only half of the cleavage stage embryos (day 3) have the ability to continue to develop in the laboratory environment for 2-4 days to form blastocysts.

If the embryos on the third day can continue to grow into blastocysts in the laboratory, this can obviously improve the live birth rate. butIn fact, not all meiosis embryos can develop into blastocysts, not even the last one. Research data shows that 9% of women may end up with no available blastocyst.

Who is suitable for blastocyst transplantation?

1,In the past, many embryo transfers but repeated implantation failed. Those suspected of insufficient embryo development potential can choose to use 4-5 embryos for blastocyst culture to further understand the embryo development potential, and select developed embryos for transfer to increase the chance of pregnancy.

2,When the mother-to-be is due to some physical reasons, such as endometrium and embryo development are not synchronized, you can postpone embryo transfer, wait for fresh embryo transfer cycle for blastocyst transfer, you can use the time of blastocyst culture for buffering. Blastocyst transplantation can correct this asynchrony and increase the success rate of pregnancy.

3,Some patients with abnormal chromosomes and genes need pre-implantation genetic diagnosis, and they need to cultivate the embryo to the blastocyst stage.

4,It is expected that blastocysts can be successfully cultured, in order to optimize embryo selection and reduce the number of embryos transferred simultaneously.

5,Patients with tubal infertility, who had a history of ectopic pregnancy in the past, may consider blastocyst transplantation, because the blastocyst transfer cycle has a lower incidence of ectopic pregnancy than the fresh embryo transfer cycle.

In summary, embryo transfer and blastocyst transfer in the cleavage stage have their own advantages.

As for whether to transfer the embryo on day 3 or the blastocyst on day 5?

The best way to decide is to have a detailed discussion with your doctor, based on your own situation and the doctor's recommendations.

What do the uterus need to prepare before embryo transfer?