Preimplantation Genetic Testing (PGT)

Key Facts 

  • PGT-A is a reproductive technique used at the same time as IVF.
  • We use PGT-A to choose embryos with a normal chromosome number.
  • PGT-A is a screening test that isn’t 100% accurate. It does not tell us about any other genetic conditions.

What are chromosomes?

Human genetic information is bundled into DNA strings called chromosomes.
A normal embryo contains 23 pairs of chromosomes. Each pair has one chromosome from the mother’s egg and one from the father’s sperm. It is a euploid embryo if there are 46 chromosomes paired into 23 pairs.
Each chromosome pair is labelled 1 to 22 with the 23rd pair being the sex chromosomes (X and Y).

What is aneuploidy?

Aneuploidy is where a chromosome pair has an extra copy or a missing copy of a chromosome rather than the usual two. This is due to random errors in division of these chromosomes.

Aneuploidy can lead to:

  • a potential miscarriage,
  • failure of the embryo to implant into your uterus or
  • a baby being born with a condition. One example of this is Down syndrome where the embryo has an extra chromosome 21.

With PGT-A, we can detect this error in chromosome number. This is why it is also known as 24 chromosome screening.

Who is PGT-A suitable for?

  • People with a history of recurrent implantation failure
  • Women of older age and are expected to develop a good number of blastocysts during IVF treatment.

What happens in PGT-A?

  1. After egg collection and insemination, the embryos are grown in the lab for 5-7 days.
  2. We biopsy an embryo on day 5, 6 or 7. This biopsy involves taking a few cells from the trophectoderm of the embryo.  The trophectoderm is the outer cell layer of the embryo that later develops into the placenta. The risks of damaging the embryo with this technique are thought to be minimal.
  3. These cells are then sent to an accredited diagnostic genetic testing laboratory.
  4. The embryos are frozen and stored in our IVF laboratory while we wait for the results, which take up to 6 weeks.
  5. If your results show that your embryo is suitable for transfer, you may have a frozen embryo transfer.
  6. Unused embryos will remain in storage.
  7. We will talk to you about what you would like to do with embryos with abnormal results. If aneuploidy is detected, an embryo will not be suitable to transfer.

What are the limitations of PGT-A?

Embyros

  • You may not have blastocysts that are suitable to be biopsied.
  • You may have no embryos that are suitable for transfer.
  • Some embryos may not survive being frozen and thawed.
  • Risk of embryo damage – there is a very small risk that the biopsy procedure may cause damage to the embryo.
  • There is a possibility of a mosaic result. This is when some cells in the embryo biopsy have a different number of chromosomes compared to other cells.  If this happens, it does not necessary mean that embryos cannot be transferred.  You would need to have a further detailed talk with a genetic counsellor.
  • Sometimes there is no result obtained for an embryo. You may choose to transfer this embryo despite not knowing the results.
  • Euploid embryos are not guaranteed to result in a pregnancy.
  • It is possible that undergoing PGT-A will reduce the number of embryo transfers required in order to conceive an ongoing pregnancy.
  • For some patients, PGT-A may shorten the time to pregnancy by avoiding multiple embryo transfers. However, the evidence shows that the time to achieving a pregnancy for most patients may be longer due to the additional time taken to carry out the genetic testing.

Limited testing

  • There maybe other genetic conditions or birth defects present which PGT-A does not test for.
  • PGT-A is not 100% accurate. The accuracy is shown to vary from 90-99% depending on the test type that is used.
  • We recommend routine prenatal screening after PGT-A.
  • PGT-A cannot be used for sex selection of the embryo unless there is a pre-existing sex-linked condition in the parents. This must be approved by an ethics committee.

What are the costs?

PGT-A is not publicly funded. PGT-A has an additional cost to that of an IVF cycle. 

It is $1470 per embryo for the 1st, 2nd and 3rd embryo, and from the 4th embryo onwards it is $840 per embryo. Price includes the courier fee.

How do I arrange PGT-A with the laboratory?

If you have been considering PGT-A, you will need to let the laboratory know you wish to proceed. You must inform us at Book On in order to be booked in with the lab. The best way to communicate about PGT-A is by email fertlab@adhb.govt.nz.
If you have not let us know, your IVF cycle may proceed as normal but without PGT-A.

Please see this website from The University of Melbourne to assist you in making an informed decision. The website uses the latest research, explains the benefits and risks, and offers clear, independent, expert-backed information.

PGT-A (Preimplantation Genetic Testing for Aneuploidy) (PGT-A testing) | Evidence-based IVF