PGS method suggests
- Ovarian stimulation egg collection IVF or ICSI
- Growing embryos to day 5 blastocyst stage
- Embryo biopsy on day 5 and immediate freezing of blastocysts after biopsy via vitrification
Steps 1-3 can be repeated as many times as necessary to collect as many blastocysts as required for your age group to have a high chance to find at least one euploid embryo among the studied group. Please see the table “embryo banking” to find how many embryos may be needed for testing in your age group
- Testing of samples from all the biopsied embryos for 23 chromosome pairs.
- Within 1 month after the last egg collection we provide you with the PGS result.
- If there is at least one euploid embryo available, we perform frozen embryo transfer during your one day visit at your convenience.
More about PGS methodology you can read here:
Embryo biopsy on day 5
Until recently embryo biopsy was generally performed on day 3 in 8 cell stage. This timing of biopsy made it possible to receive the result of genetic test before day 5 and to perform fresh embryo transfer on day 5.
In 2011 Treff at al. has shown that day 3 biopsy itself reduces embryos’ capability to attach at least by 42%. At the same time biopsy on day 5 has not influenced the implantation rate in comparison to control.
|Implantation rate||Cleavage stage (day 3)||Blastocyst stage (day 5)|
The major advantage of blastocyst biopsy (day 5) in comparison to the cleavage stage biopsy (day 3) is a reduced impact of biopsy on the embryo viability
Vitrification of biopsied blastocysts
Biopsy on day 5 has risen a new challenge: either to obtain the genetic result very quickly and perform the embryo transfer on the morning of day 6, or to cryopreserve an embryo until the result of genetic test for 23 chromosome pairs is obtained.
Fresh embryo transfer on day 6 seems to be less effective than frozen embryo transfer of 5 day blastocysts due to the fact that the implantation window is often missed.
Vitrification of blastocysts immediately after biopsy provides a unique opportunity to win time for testing their material, obtained through the biopsy, and at the same time not to compromise implantation opportunity due to transferring embryos into advanced endometrium. Of course it is very important that the procedure of embryo freezing is well established. At AVA-Peter we have 95% survival rate of blastocysts after freezing- thawing and 45% of clinical pregnancy rate after frozen embryo transfer in all patient groups (without PGS).
Is frozen transfer as good as fresh?
A randomized control trial has been performed comparing transfer of 1 euploid blastocyst fresh vs frozen [Forman et al 2013]. Clinical pregnancy rate with one fresh euploid blastocyst was 65% and with a frozen euploid blastocyst – 55%.
Clinical results achieved with vitrification
[Schoolcraft et al., 2010]
|Cycles||Maternal age||Previous failed cycles||Embryos replaces||Implantation (fetal sac at scan)|
Advantages of FET:
- Endometrial receptivity potentially better in FET cycle
- Allows embryo banking: more embryos to select , less risk of having no embryos for transfer
- Reduces cost of test per embryo due to embryo banking