Genetic Testing – An Expert Explains
July 2, 2022
Genetic testing – an expert explains
Over the past three decades, around 390,000 babies have been born from IVF or donor insemination (DI) cycles in the UK.
Since then, innovations have been developed in order to optimise this process. These tests and services are sometimes called ‘add-ons’. They are offered by fertility clinics claiming they can help your treatment in one way or another.
If you’re considering or having fertility treatment, you may be offered a wide range of ‘add-ons’. These might include genetic testing for chromosomal abnormalities. It can be tricky to know what’s worth the money, what has sufficient evidence behind it and indeed what you really could benefit from.
Geneticist Dr Alan Thornhill has all you need to know in this fascinating series.
Welcome to your genetic testing series
Welcome to Genetic testing – an expert explains, a series designed to help you understand the significance of these screenings, covering the stages from embryo to newborn.
About me
I’m Dr Alan Thornhill and I’ve been involved in IVF, fertility and genetics for 30 years, working in research and embryology labs, IVF clinics and the HFEA – the UK’s fertility regulator.
I now run a genetics laboratory focused on providing tests to help people make informed choices about building healthy families, quickly and with fewer obstacles along the way.
I believe that the main reason why couples don’t get access to the latest advances in genetics is because of a knowledge gap. Most patients (and even their healthcare providers) aren’t aware of what is available and how to access it.
That’s why I’ve created this series – to try and close that gap.
Let’s get back to basics…
Genetics is the study of genes, and these are the biological instructions your body uses to make you and your baby.
While not everything is governed by your genetics, a lot is – including your early development.
For every person, this set of genetic instructions is encoded in your DNA as thousands of genes, each responsible for their own part of the puzzle and packaged into a set of chromosomes.
You generally have 23 pairs of these chromosomes, including two X chromosomes in people born biologically female, or an X and a Y chromosome for those born biologically male.
An alteration in DNA (also known as a mutation) encoding a particular gene can lead to a specific genetic disease.
For example, gene mutations involved in the production of haemoglobin – the substance that makes your blood red and helps to carry oxygen around our body – are linked to diseases such as:
- sickle cell anaemia – a condition which affects how oxygen is carried throughout your body.
- thalassemia – a disorder in your blood which causes your body to produce less haemoglobin than normal.
Chromosome abnormalities during early cell division in embryos lead to additional chromosomes or fewer chromosomes than normal.
In most cases, these abnormalities prevent further development of the embryo and the pregnancy fails. This is one of the most common causes of IVF failure.
More rare, but much more noticeable, is when a chromosomally abnormal embryo results in the birth of a child with profound health issues and disabilities, such as Down’s syndrome – when a child has an extra copy of their 21st chromosome (which is more likely to occur in older mothers).
For most people, the chances of having a healthy child are higher than those of having a child with genetic disease.
Why is genetic testing used?
Changes in genes can have severe impacts on your health – sometimes with life-threatening consequences.
By identifying these changes, you may be more prepared regarding your baby’s future and make alternative choices if necessary.
Aside from detecting when something isn’t quite right, screenings can also give you a clearer understanding of normal variation in your body’s genetics so that any IVF treatment can be personalised to you in the hopes of improving your chances of success.
Many genetic tests are now available, accessible and affordable to minimise your risks of having a child with a genetic disease and to improve your odds of having a child in less time with fewer adverse outcomes.
It’s important to note that some of these additional treatments (often called add-ons in fertility clinics) are optional. They also may not have evidence from high-quality randomised control trials (RCTs – the gold standard of medical evidence) to prove their effectiveness.
Read more about treatment add-ons here.
What you’ll be getting from this series
I’ll be outlining each of the following genetic tests available in the UK – what they are and how they work:
- Pre-implantation genetic testing for monogenic disease (PGT-M)
- Pre-implantation genetic testing for aneuploidy (PGT-A)
- Endometrial receptivity analysis (ERA)
- Non-Invasive prenatal testing (NIPT)
- Products of conception (POC)
- Newborn screening
I’ll also be discussing why they’re performed, as well as their suitability, risks and costs. I hope I can help make the world of genetic testing a little clearer for you with this series.
What is PGT-M?
It’s estimated that 1 in 25 children is affected by a genetic condition. PGT-M is used to minimise this risk before conception, but what exactly is the test?
You may have an inherited disease in your family, such as cystic fibrosis or sickle cell anaemia, that you could pass on to your future children. This is where PGT-M could be an option for you.
Preimplantation genetic testing for monogenic disease (PGT-M), previously called PGD, aims to diagnose ‘affected’ embryos in an IVF cycle through a selection process.
PGT-M allows the transfer of unaffected embryos instead of affected ones – but the test itself can’t improve the quality of your embryo.
There are benefits but success rates after these screenings could be lower than if you conceived naturally or went through IVF without testing. This is because fewer embryos are available for transfer once you have selected only unaffected embryos.
It’s important to note that this test doesn’t check whether the embryo has any possible genetic disease. PGT-M detects genetic alterations that could potentially lead to a specific genetic disease that you are at a high risk of passing on.
The UK fertility regulator HFEA strictly licences PGT-M only for severe diseases that have a high likelihood of transmission.
Who might be recommended for this type of screening?
You’d be recommended for PGT-M if you’re at risk of passing a genetic disease to your future children and you wish to use your own sperm and eggs – while avoiding the difficult choice of terminating your pregnancy.
Regulations for this type of testing are strict in the UK, so you’d only be eligible if you have a high risk of transmitting a genetic disease (often considered as a 25% or more chance).
There are many new genetic diseases still being discovered, so if your specific genetic disease hasn’t yet been approved by the HFEA, a genetics professional may be able to apply for a specific licence for you to get tested.
Are there any risks?
There are no physical risks to you directly, other than those present for IVF.
However, there is a risk that you may have fewer or no embryos available for transfer if some or all embryos are reported as affected.
If these embryos were incorrectly reported as abnormal (false positives), there is a possibility that you would discard a potentially normal embryo.
In contrast, if any embryos were incorrectly reported as normal (false negatives), there is a chance that you could have a child with the genetic disorder you were trying to avoid. Fortunately, these risks are very low.
There is also a chance of your embryo becoming damaged during the biopsy procedure, but this risk is small and varies according to the skill of your embryologist.
Is it available on the NHS?
Yes, PGT-M is currently funded by the NHS for up to three cycles of IVF treatment, but you may only be eligible for testing at a limited number of clinics and could be put on a long waiting list.
As with IVF, depending on where you live, there may be different eligibility criteria and access to healthcare centres that can provide this specialist treatment.
PGT-M can also be accessed in private clinics that charge a flat fee of roughly £4,000 to £5,000 per cycle, in addition to your IVF costs.
What is PGT-A?
If you are considering IVF, you may have heard of the screening test PGT-A. But what is it and how effective is it?
Chromosomal abnormalities are the most common cause of IVF failure, and their incidence increases dramatically with your age. PGT-A aims to serve as a selection tool to combat this.
Pre-implantation genetic testing for aneuploidy (PGT-A), previously called PGS, screens embryos made in an IVF cycle, and helps identify which embryos should or shouldn’t be transferred.
While there are many studies published , the HFEA says there is no sufficient high-quality evidence yet to justify its routine use in IVF. However, in specific cases, there may be good reasons to perform this test.
Read more about treatment add-ons here
While PGT-A cannot improve the embryo quality or increase your chance of success overall, there is evidence that, as a selection tool, PGT-A may lower your chances of miscarriage and reduce the time to achieve pregnancy.
Who might be recommended for this type of screening?
You are most likely to benefit from PGT-A if you are 35 or older.
Other reasons for testing may include patients with a history of miscarriage, severe male factor infertility (where no sperm is found in the semen) or repeated IVF failure.
Are there any risks?
There are no physical risks to you directly, other than those present for IVF.
However, there is a risk that you may have fewer or no embryos available for transfer if some or all embryos are reported as abnormal.
If these embryos were incorrectly reported as abnormal (‘false positives’), there is a chance that you would discard a potentially normal embryo.
There is also a small possibility that your embryo could be damaged during the biopsy procedure. But, this risk is small and varies according to the skill of your embryologist.
Is it available on the NHS?
No, PGT-A is not currently NHS-funded, and in most cases, you won’t be able to add it to a NHS-funded IVF cycle – even if you’re willing to pay for it.
In the UK, clinics charge their patients for PGT-A by either:
- setting a fee for an average number of embryos tested, between £2,500 and £4,500 per round of testing;
- adding a biopsy fee per embryo tested. For example, the biopsy fee might be £1,500, with an additional per embryo tested fee up to £450.
There is wide variation in the pricing models between clinics, so try to find out the costs as soon as possible to avoid any surprises.
What is ERA?
ERA looks at whether your endometrium is receptive for embryo implantation. Find out if this test is relevant in your fertility treatment.
Since IVF was discovered, much of the research has focused on the embryo. If you consider the embryo as a seed, then it makes little sense to put a good seed in poor soil or to plant it at the wrong time.
A renewed focus on the endometrium or lining of the uterus (where the embryo needs to implant) has led to the development of new tests.
Endometrial Receptivity Analysis (ERA) is one such test. It aims to identify the optimal timing for an embryo transfer in a frozen-thaw IVF cycle.
The window of implantation is the period when the endometrium is ready for an embryo to implant and start to develop into a foetus.
It’s likely you have a window of implantation that is open (receptive) after five full days of exposure to progesterone (used to prepare the lining of your uterus) in a medicated cycle. But if you have a displaced window, you’ll need longer or shorter exposure to this hormone before your embryo transfer.
Using ERA to help find the best timing for transfer is known as a ‘personalised embryo transfer’.
While there are many studies published, the HFEA says there is no sufficient high-quality evidence yet to justify its routine use in IVF. However, in specific cases, there may be good reasons to perform this test.
Who might be recommended for this type of screening?
ERA may be used if you have had repeated implantation failure; defined as three or more failed transfers involving good-quality embryos.
Are there any risks?
You’ll need to undergo a standard endometrial biopsy, which carries a very small risk of bleeding or infection. The biopsy is usually performed after a medicated hormone replacement therapy (HRT) cycle.
Aside from its benefits in dealing with symptoms of menopause, HRT is also used in IVF to help prepare your uterus for the embryo transfer process.
Is it available on the NHS?
No, ERA is not currently funded by the NHS, and in most cases, you won’t be able to add it to a NHS-funded IVF cycle – even if you’re willing to pay for it.
The test is available in most private IVF clinics in the UK, charging between £900 and £1,500.
Please check whether this fee includes the cost of a medicated testing cycle, scans, blood tests and an endometrial biopsy, as these procedures can incur additional costs.