PGT-A (Genetic testing)

PGT-A – Preimplantation Genetic Testing for Aneuploidy

PGT-A (previously known as preimplantation genetic screening or PGS) is a screening test used to determine the chromosomal status of an embryo by screening all 23 chromosome pairs prior to transfer in an IVF cycle.

How does it work?

A healthy human has 23 pairs of chromosomes (46 in total), which in total make up the human genome. It has been shown that any alteration in the number of chromosomes through gains or losses, is the leading cause of failure to implant (failure to get pregnant) and miscarriage. Each person inherits one half of the pair through their mother (via the egg) and one half from the father (via the sperm) which come together after fertilisation. Five days after fertilisation, the embryo has differentiated into two distinct parts: the inner cell mass, which will go on to form the baby, and the trophectoderm, which will form the placenta.

Approximately five cells of the trophectoderm (placenta) are carefully removed and analysed to assess the chromosomal number of the embryo. This ensures only those embryos shown to be carrying the normal complement of 23 pairs of chromosomes are chosen for transfer.

Is it right for me? 

All couples produce a mixture of chromosomally normal embryos (euploid) and embryos where there is an additional or lost copy of a chromosome (aneuploid). However, the frequency of aneuploid embryos increases greatly with age. On average, a woman of 35 will have equal numbers of both; by the age of 38, 70% are aneuploid. Any chromosome can be affected and it is impossible to tell simply by looking whether it carries an aneuploidy or not.

You might consider PGT-A for any of these reasons:

  • Recurrent miscarriage – natural or IVF-cycle miscarriage.
  • Repeated implantation failure.
  • Advanced maternal age
  • Couples interested in giving themselves the highest chance of success from a single embryo transfer

What next?

An initial consultation with one of our fertility specialists will take place to agree your personalised treatment plan. PGT-A requires a hormonal stimulation cycle followed by fertilisation with either IVF or ICSI. Embryos then need to reach the blastocysts stage to undergo the test. Any normal embryos are frozen for thawing and transfer in any subsequent cycle.

Our fertility specialists will offer advice on cycle management to ensure optimal times for embryo biopsy and embryo transfer. You’ll be able to take a pregnancy test two weeks after embryo transfer. If this is positive, you’ll have a pregnancy scan at Bourn Hall about 35 days after the initial procedure.

Get in touch

To learn more, contact our patient services team on 01954 717210 or complete the form below by clicking ‘get in touch’.