The blastocyst is the embryo that has reached approximately the 5th day of development after fertilization. At this stage, the embryo has successfully continued cell divisions, has increased in size and now consists of 50 to 200 cells. A characteristic cavity forms inside it, while the cells have already begun to differentiate.
The embryo is being prepared for hatching from its protective shell, so that it can implant in the endometrium.

Advantages of Culture to Blastocyst

Monitoring and supporting embryos until day 5 offers significant benefits:

• Better timing with the endometrium
  The endometrium is normally at the ideal stage for implantation around the 5th day after ovulation.

• Favourable environment for implantation
  Progesterone reduces uterine contractions, which facilitates the stabilization of the embryo.

• Selecting embryos with higher developmental potential
  Embryos that manage to reach the blastocyst stage naturally have already proven to have better quality and a higher probability of successful implantation.
  This allows us to select the most suitable embryo for embryo transfer.

Possible Limitations

Although blastocyst culture has clear advantages, there are also points that need careful evaluation:

• Not all embryos develop the same
  Some embryos may not reach the blastocyst stage in the laboratory, even though they would likely develop normally in the uterine environment.

• Smaller number of embryos for cryopreservation
  Because only a portion of embryos reach day 5, there may be fewer embryos available for freezing.