Pre-implantation genetic testing for aneuploidy (PGT-A) is a genetic screening test performed on embryos produced during an IVF treatment cycle. PGT-A gives information about your embryo’s genetic health to help us select healthy embryos for transfer.
We may recommend PGT-A if you have
Every cell in an embryo should contain 23 pairs of chromosomes – 46 chromosomes in total, known as euploid. One chromosome from each pair comes from the sperm and one from the egg that creates the embryo. As the cells of the embryo divide the chromosomes are copied and each new cell contains an identical copy of the same 46 chromosomes.
Sometimes, the sperm or egg that form an embryo has fewer or more than 23 chromosomes and because of this, the resulting embryo also has too few or too many chromosomes, known as aneuploid. These embryos may fail to develop or develop in the laboratory but fail to implant or implant but lead to pregnancy loss. Sometimes, an embryo with more or fewer than 46 chromosomes can develop to term but the baby is affected by a serious condition like Down’s syndrome (where there are three copies of chromosome 21) or Turner’s syndrome (which occurs when girls inherit only one X chromosome and so have only 45 rather than 46 chromosomes).
Embryos are produced through an IVF cycle.
5-6 days after fertilisation, embryos should reach the blastocyst stage. Blastocysts contain approximately 100 to 200 cells arranged into an inner cell mass and an outer ring of cells called the trophectoderm. The inner cell mass is made up of undifferentiated stem cells that will go on to form the foetus. The trophectoderm is a layer of cells that will become the placenta. A few trophectoderm cells are carefully removed by our embryologists and sent to the genetics laboratory for assessment, while we freeze your embryos and keep them safe.
To view a biopsy video, please click here
To freeze and thaw your embryos, a process called ‘vitrification’ is used. Vitrification involves much more rapid cooling than other less advanced methods of freezing, and it prevents ice crystals from forming. This preserves the quality of the cells and improves the chances of success when they are thawed. Vitrification has greatly improved the success of embryo freezing and it’s now a very reliable practice.
Testing is carried out using cutting-edge technology to analyse the number of chromosomes present within the embryo’s cells.
Embryos that are identified as having the correct number of chromosomes and therefore most likely to result in a healthy baby, are selected for transfer. Alternatively, your embryos can be frozen for future use.
[1] Based on 573 single euploid embryo transfers resulting in 281 pregnancies with a foetal heartbeat
[2] Based on 2645 embryo transfers resulting in 1016 pregnancies with a foetal heartbeat
Genetic testing for IVF is an eight-step process that takes place as part of a regular IVF cycle.
We’ll artificially stimulate your ovaries to produce several eggs for testing
When the time is right, we’ll retrieve your eggs and inspect them to see which ones are mature and suitable for screening.
The extracted eggs will be injected with sperm.
On the day after insemination, we’ll check to see if fertilisation has taken place.
Successfully fertilised eggs will be grown in a laboratory for around one week, allowing the embryos to form. We’ll then extract the cells that will go on to form the placenta. This should not harm the embryo in any way, and will be carried out by a specialist embryologist.
The removed cells are tested for any abnormalities.
Only the embryos that have shown no abnormalities during our genetic screening will be transferred to the woman’s uterus. We’ll transfer one embryo at a time, and freeze any other unaffected embryos for potential later use.
Twelve days after we’ve transferred the embryo, you will be given a pregnancy test to see if your embryo has successfully implanted.
The cost of genetic testing depends on whether you need PGT-A or PGT-M, and what other stages of IVF you’re going through. Take a look at all our pricing options to get a clearer idea of costs.
How effective is PGT-A?
The independent regulator of fertility treatment, the Human Fertilisation and Embryology Authority (HFEA), has developed a ‘red-amber-green’ rating system and provides information on their website about treatments that are offered on top of your routine fertility treatment – known as treatment add-ons. They consider that the only way to be confident that a treatment is effective enough to be used routinely is to carry out a randomised controlled trial (RCT). In an RCT, patients are assigned randomly to two groups: a treatment group, given the new treatment and a control group, given either a well-tried treatment or a placebo.
The HFEA has given PGT-A a red rating because it considers that there is no evidence from such trials that PGT-A increases the overall chances of having a baby. There is information on the HFEA website about PGT-A and its risks and benefits that you may find useful to consider.
Our partners, Care Fertility did participate in a large scale RCT called the STAR trial, which was published in December 2019. This trial concluded that there was a significant increase in pregnancy rate in a subset of women aged 35–40 where they had more than two embryos available for testing, although overall in all age groups there was no increase in ongoing pregnancy. However, we recognise that that more robust clinical and laboratory trials are needed to prove whether or not PGT-A significantly increases live birth rates.
Get in touch with one of our dedicated IVF advisers for more information on this, and how we can help you conceive.
At Zita West Clinic, we understand that each individual person needs an individual approach to starting a family. From the moment you walk through our door, you will receive personalised and comprehensive guidance and advice to help you through your fertility journey: the future of your family starts here.