Blastocyst Transfer Stage in IVF Treatment

Embryos in blastocyst stage are obtained in the laboratory environment on the 5th or 6th day after fertilization.

After this period, it is not possible to culture embryos in a laboratory environment. Transfer to the mother's uterus is required. Embryo gets rid of its protective layer, called the zona pellucida, and begins to adhere to the uterine tissue 6 to 7 days after transfer.

Embryos in blastocyst stage have a multicellular structure (100-120) consisting of the inner cell mass that forms the fetus (baby) and the trophectoderm cells that form the placenta. Embryos that have reached this stage are classified by the quality of the inner cell mass and trophectoderm structure. When both are of good quality, the transfer of such embryos may result in much higher pregnancy rates. Besides, embryos that have reached the blastocyst stage can be successfully frozen by vitrification, an ultra-fast freezing method, and can be successfully thawed when needed.

BLASTOCYST (5th day embryo) TRANSFER

Embryos that are followed and developed in the laboratory for 5 days are called blastocysts. Embryo transfer performed on the 5th day is then called blastocyst transfer.

We have witnessed dazzling scientific developments since the first successful IVF application in 1978 until today.

The 5th day blastocyst transfer, which is one of the advanced in vitro fertilization techniques used today, offers a much higher chance of pregnancy to couples who want to have children.

In all countries, legal restrictions have been imposed on the number of embryos transferred in order to get rid of the risks of multiple pregnancy. In our country, this limit is at most 2 embryos. By giving 1 or 2 blastocysts in embryo transfer on the 5th day, both the risk of multiple pregnancy is reduced and the chance of pregnancy is increased. Embryos with chromosomal abnormalities are much less likely to reach the blastocyst stage than normal embryos. Thereby, the probability of selecting chromosomally healthier embryos in 5 days is high. Therefore, with the 5th day transfer, higher implantation (attachment to the mother's uterus) and pregnancy rates can be achieved.

However, in order to be able to transfer blastocysts on the 5th day and achieve successful results, the IVF unit must have the following high-qualifications:

– Laboratory conditions must be at the highest level. Design, ventilation, cleaning and their periodic controls must be done without errors.

– Laboratory should have sufficient and quality equipment. All equipment should be checked and calibrated regularly.

– There must have a professional experienced team in their fields.

- There should be sufficient number of embryologists experienced in techniques that require meticulous follow-up, such as blastocyst transfer.

– An IVF unit should routinely follow the technological innovations that are constantly being renewed. They should be able to apply advanced in vitro fertilization techniques that have a direct effect on quality embryo development. For example, sperm selection with the IMSI method, which is applied for the first time in our country in the Brussels IVF Unit, positively affects quality blastocyst development (For more information, you can read our article titled IMSI).


It can be applied to all couples where the number of fertilized eggs is high (generally 7 and more) and the 2nd day embryo quality is good. The 5th day blastocyst transfer is recommended to suitable couples following the consultation of doctors and embryologists who know the patient's history on the day after the fertilization process.

In our unit, blastocyst transfer is performed very successfully and very high pregnancy rates are achieved. Besides, the remaining quality embryos after the transfer are successfully frozen with the advanced cellular freezing technique, the vitrification method, and a second chance is offered to the couples.


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