The biggest challenge in IVF success is to select the best embryo for transfer which will develop as a normal pregnancy. Most common reason for embryos not implanting is a genetic abnormality in the embryos.
There are very good monitoring parameters to judge which embryo is better. That includes egg quality, embryo development speed, embryo quality etc. However, better techniques are required.
Culturing the embryos in IVF lab till blastocyst stage – blastocyst culture, Preimplantation genetic testing – PGS– PGT – A, are the two best options. Blastocyst culture has many advantages over PGS. It is non-invasive on embryos, simpler to do, much less expensive also. The limitation is that it does not tell about the actual genetic constitution of the embryos.
Blastocyst and natural pregnancy
When an embryo becomes 5 to 6 days old, it reaches a stage of development which is called “ BLASTOCYST ”. In natural conception, the sperm fertilizes the egg in the fallopian tube. The embryo grows in the fallopian tube and slowly moves towards the uterus. An embryo reaches the uterus – endometrium after 4 to 6 days of fertilization at the blastocyst stage.
What is a Blastocyst?
All embryos which look good on day 2 or 3 of development may not develop further. If we culture them for more days, only the good quality embryos of them may develop further and reach the blastocyst stage successfully. The remaining stop developing at various stages in between. It is impossible to know which embryos will reach the blastocyst stage.
We can select and transfer one or two blastocysts and still achieve a very good pregnancy rate. This is called Blastocyst Culture.
Why Blastocyst culture?
Embryos selected by blastocyst culture have higher chances of implantation.
We know that only a few and not all of the transferred embryos can develop further and result in pregnancies. To compensate for this “stopped development” of a few embryos, we transfer more embryos at the 4 to 8 cell stage to achieve a better pregnancy rate. When we transfer more embryos, the chance of pregnancy increases, but at the same time, there is a significant increase in the chance of having multiple pregnancies, including higher-order multiple pregnancies.
Suppose we can select the embryos by blastocyst culture. In that case, we can transfer fewer embryos and still get a better pregnancy chance. We can reduce the chance of multiple pregnancies significantly.
Also, for patients who opt for preimplantation genetic testing PGS/PGD – PGT-A, PGT-M, PGT-SR technique, we have to do blastocyst culture and transfer of normal blastocyst.