What is Blastocyst Culture?
Normally, in standard IVF or ICSI cycles, the embryos are transferred back into the womb, on the second or third day after egg collection. This standardized method of day 2 or day 3 transfer yields good pregnancy rates.
However this method has some disadvantages:
- In the natural cycle the embryo is conceived in the fallopian tube. After this it takes 4 days for it to travel to the womb. By this time the embryo develops into mature stage called the Blastocyst, which then implants into the lining of the womb. In standard IVF or ICSI, we put back the embryos 2-3 days before they reach the Blastocyst stage. By putting the embryos back at the Blastocyst stage, there is an increase in pregnancy rates.
- When we put back the embryos on day 2 or day 3, we are not very sure as to which embryo is viable or will survive and grow to the Blastocyst stage and be implanted. Hence we tend to place 2 to 4 embryos into the womb, to try and increase the pregnancy rates. This results in an increase in pregnancy rates, but also gives rise to increase incidence of multiple pregnancies. Multiple pregnancies have their own set of problems such as miscarriage and pre-term births.
Keeping in view, the above, many units, including ours, are now growing embryos in the Incubator, for 5 days, till they reach the mature Blastocyst stage, and then placing them back into the womb. This is known as Blastocyst transfer.
How is Blastocyst Culture done?
Major steps in the sequence are:
- Monitor the development of ripening egg(s) in the ovaries.
- Collect eggs.
- Obtain sperm.
- Put eggs and sperm together in the laboratory, and provide correct conditions for fertilization and early embryo growth. (Through the IVF or ICSI procedure)
- The embryos obtained on Day 2 (2-4 cell stage) are placed in special sequential culture media and grown to Blastocyst stage. This takes 5 to 6 days after egg retrieval.
- Normally 50 -60% of embryos develop into Blastocyst.
- Two good quality Blastocyst are then selected, loaded into the transfer catheter and standard embryo transfer is done.
- The remaining Blastocyst can be frozen for later use, in subsequent cycles.
- Occasionally, prior to embryo transfer, the cover of the Blastocyst may be cut with a Laser or may be dissolved with an enzyme called Pronase. Research has shown this to increase pregnancy rates.
Why is Blastocyst culture not done routinely for all patients?
In 20 -30 % of patients, none of the embryos develop into Blastocyst. In these patients, there would be no viable embryo, available for embryo transfer. In such a patient the pregnancy chance will be zero.
This is a relatively new technique, and one does not know whether there would be long term adverse effects in exposing embryos for 5 days to the environment. At the same time, it would be important to note that there has been no increase in abnormalities in Blastocyst babies as compared to day 2/3 transfer babies.
Who would qualify for Blastocyst Culture?
- Patients have failed to get pregnant after IVF/ICSI cycles
- In patients who have more than 3 Grade 1 /Grade 2 good 6-8 cell embryos on day 3 after egg retrieval. In these cases, Blastocyst culture will help in selecting better, genetically more normal embryos and also help in reducing multiple births. This is the main criteria for perfoming Blastocyst, at the Babies And Us Fertility Centre.
- In patients who want to undergo Pre-implantation Genetics.
It is important to counsel the patient about the occasional risk of zero Blastocyst formation and hence zero pregnancy.
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