Blastocyst Transfer (5th Day)

Blastocyst Transfer

"Blastocyst Transfer", which is one of the advanced assisted reproduction techniques, offers couples with infertility problems an increased chance of having a baby. The first test-tube pregnancy, which was accomplished successfully as a result of studies carried out in 1978, was obtained by "blastocyst transfer".

Then, What Is ‘Blastocyst Transfer’?

Successful results can be achieved via IVF in infertility, which is a growing health problem in the world and in Turkey. IVF is the injection of a sperm cell into each egg cell with a method called microinjection in the laboratory. Fertilization of the egg results in the formation of an embryo. Embryos; which are grown in the laboratory environment for 5 days under close monitoring, are called "blastocysts". When an embryo becomes a blastocyst, it consists of 100-120 cells.

When the inseminated egg is examined 16-18 hours after the fertilization in the laboratory environment, two nuclei are seen inside the fertilized egg (zygote). Later, these nuclei merge and dissolve and the fertilized egg itself begins to divide. It continues to divide and the number of cells start increasing in the following numbers as 2, 4, 8, 16, etc.

After day 3, the number of cells of the embryo are too many to count.

In the evening of day 4 or later, a cavity becomes to develop in the center. Usually on the fifth day, a fluid-filled cavity occurs and the BLASTOCYST is formed consisting of two groups of cells; which are the inner cell mass and the trophectoderm that will develop into the baby and the placenta, respectively.


The embryo at the blastocyst stage is larger than the cleavage-stage embryo. Blastocyst becomes ready for implantation in the intrauterine cavity when it starts leaving "Zona Pellucida", which the surrounding  protective membrane.

Obtaining the Blastocyst

Early in the IVF practice previously, embryo transfer was performed only at the cleavage stage (2nd or 3rd day after fertilization). On the 3rd day of embryo; it is not possible to understand exactly, which of the obtained embryos are more suitable for transfer to achieve pregnancy. Today, embryos can be conveniently grown to the blastocyst stage by means of technical advances in laboratory equipment, the piled up knowledge about the embryo, and improvements in solutions used in embryo culture. Embryos can be left for growing for 2 more days after the third day so that embryos with a higher chance of attaching to the uterus can be obtained. Only healthy embryos can keep up growing by the 5th day. Furthermore, the risk of carrying a genetic defect/chromosomal abnormality is significantly lower for 5-day-old embryos compared to the 3-day old embryos.

Does Blastocyst Transfer Increase the Chance of Pregnancy?

Our studies and laboratory results show that a higher pregnancy rate is achieved when the embryo transfer is performed on the 5th day compared to transfers performed on the 2nd or 3rd day.

Who Is An Eligible Candidate For Blastocyst Transfer?

Blastocyst transfer may not be suitable for every patient. Blastocysts can be transferred in patients having an adequate number of high-quality embryos at the cleavage stage.

In our laboratory, 70% of embryos reach the blastocyst stage. However; advanced age or serious problems in sperms hamper blastocyst development and sometimes no blastocysts can be obtained. Blastocyst transfer schedules are cancelled in those patients. Therefore, candidate patients for blastocyst transfer should be carefully selected. Your doctor will offer optimum options specific for you and will inform you further.

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