Preimplantation Genetic Testing for Aneuploidy (PGT-A)
What is PGT-A?
PGT-A is a test for people going through IVF that can determine if an embryo contains a normal number of chromosomes. Healthy embryos should have 23 pairs of chromosomes.
What can happen if an embryo has an abnormal number of chromosomes?
If an embryo has too few or too many of any particular chromosome, it will:
- Fail to implant
- Result in a miscarriage
- Lead to offspring affected by conditions such as Down syndrome
Who can benefit from PGT-A?
Any woman going through IVF may consider PGT-A, but it can be particularly helpful if you:
> Are older than 35
> Have experienced miscarriage
> Have previously failed IVF
What are the chances that a normal embryo will be found with PGT-A?
There are 2 main factors:
- A woman’s age: The younger the patient, the greater the chance that any individual embryo will be normal. About 80% of the chromosomal problems in the embryo are due to egg quality, which significantly deteriorates with age.
- The number of embryos available for biopsy: Most eggs will not lead to embryos that will survive to the blastocyst stage. The more embryos available for testing, the more likely it is to find at least one that is normal. This is also related to age, since younger women also tend to have more eggs retrieved, and subsequently more embryos available for biopsy.
How are the embryos tested?
Embryos created by IVF are grown to the blastocyst stage 5, 6 or 7 days after fertilization. A sample of about 5-10 cells are biopsied from the portion of the embryo destined to form the placenta. The inner cell mass, which will eventually form the baby, is left unharmed.
The embryos are frozen and remain at Olive, but cells are sent to a laboratory for genetic testing. The number of chromosomes for each embryo are analyzed with a technique called “next-generation sequencing” (NGS).
What are the advantages of PGT-A?
Selecting embryos that have been identified as normal with PGT-A can:
> Increase pregnancy rates to 70% or more
> Reduce miscarriages rates to 7-10%
> Minimize risks for chromosomal abnormalities such as Down syndrome
> Allow chromosomally normal embryos to be frozen for future use
What are some of the possible limitations of PGT-A?
PGT-A can identify embryos that are chromosomally normal but even embryos that are identified as normal by PGT-A do not guarantee a pregnancy or a healthy live birth.
Other important determinants of the health of the embryo that PGT-A can’t identify include:
> Genetic conditions like cystic fibrosis
> Non-genetically determined conditions like autism
> Problems with the uterus that may prevent implantation
What are the possible outcomes of embryos tested by PGT-A?
Results will be relayed to you by a telephone call from your doctor or a genetic counsellors. Details of the results for each embryo tested will be reviewed with you at this time.
Cost
As PGT-A requires several additional steps compared to traditional IVF, there is an increase in cost. However, many experts believe that the overall advantages of PGT-A, such as improved pregnancy rates and decreased miscarriage rates, will result in an overall cost benefit.
The Olive accounting department will discuss the expenses in detail.
I am interested in PGT-A what are my next steps?
If you have not already done so, have a discussion with Dr Van Tongeren. Genetic counsellors are also available for additional discussions if necessary.