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Conception Pregnancy Feb 27, 2020
6 Minutes

Genetic testing: what you really need to know…

The growth in modern technology continues apace. Sometimes it’s great, sometimes it’s not so great. What is the real deal when it comes to the advances in genetic testing? Tests that can now happen throughout the journey from pre conception, during IVF and pregnancy and even post. We take a balanced look at the facts and help you decide what is right for you for every stage of the journey.

Don’t worry we promise you won’t need a degree in genetics to understand this! We’re gunna break it down…

Let’s start at the very beginning with a genetic test open to everyone preconception: CarrierMatch…. 

So what is it?

In a nutshell this is a test you can do at the very beginning of your journey to identify high risk of genetic abnormalities that can occur when both parties carry the same type of gene for a particular condition. Everyone can have this test done ahead of trying to conceive. This can also be done if you’re doing egg/sperm donation – you just need to know who you’re picking! It is a simple blood test. 

A few things to know: 

So we know that genes are responsible for expressing pretty much everything in our bodies. In a serious nutshell (!) you get dominant genes that will override everything and express themselves (you are likely to see whatever they express in yourself or in your partner). Recessive ones that will only be expressed if they are matched with another (your partner’s). These you can say are potentially ‘hidden’.

One example is blue eyes – they only come out if both parents have the recessive gene for blue eyes. Brown eyes are dominant however and if one person has them they are more likely to override and get expressed in a child.

So CarrierMatching is mainly looking for these ‘hidden’ recessive genes and working out whether or not you and your partner may have a matching one that could be potentially expressed in a child in a way that we might not wish.

Why would you choose to get this done? 

This particular test will only look for severe genetic diseases like Cystic Fibrosis or Sickle Cell. It won’t catch everything (it looks at around 600 genes). But can of course be a way to reduce your risks. It is open to everyone. People who are doing IVF may choose to do this, or those using donors or couples who are in some way related.

What happens if I get a result I don’t like? 

If you do show as having risk of a particular disease with your partner you can either choose another donor (if that’s the route you’re going) or you can then go on to have Pre Genetic Diagnosis (PGD) to test embryos more closely. The important thing to note however is that this is not enormously common.

Next up: testing the eggs: Pre-Implantation Genetic Screening:

Ok so if you are using a donor egg/sperm, doing embryo freezing or IVF this is something you may wish to consider.

What is it? 

This is used to test for genetic abnormality that could cause things like failure to implant or miscarriage. So, it can improve the success rates of IVF as you are able to see which embryos are genetically normal and can choose to implant those over others.

How does it happen? 

As you can imagine this is not a simple blood test! Instead this is extracting DNA from the embryo itself. It is what’s known as an embryo ‘biopsy’. 5-10 cells will be removed from the outer edge of the embryo – known as the Trophectoderm. It happens at what is known as blastocyst stage: day 5/6. The embryos are then frozen and you will get the results in around 2 weeks.

What are the pros/cons/things to be aware of with this particular genetic test? 

So first off the pros. It has been shown to improve the chances of success as you are actively choosing embryos that are ‘genetically normal’ to implant which will have a far greater chance of survival and implantation vs those with a genetic abnormality.

The other pro is that as we get older we have more eggs/sperm cells which have genetic mutations that can lead to genetically abnormal eggs. So, once again this can save time and money and potential heartache by reducing rates of miscarriage.

The cons: it’s only 95% accurate. Still pretty good, but, because such a small amount of DNA is being taken from the outer edge there is a small chance that it is not fully representative of the whole embryo. So there is a small chance that a genetically normal embryo may be discarded.

Can this process damage the embryo? 

There is no real evidence that the process of extracting tiny amounts of DNA from the outer edge of the embryo (the future placenta) impacts the survival rates of embryos. Phew!

Ok so what about when you are pregnant? What’s the next step in genetic testing? 

Tests in early pregnancy are now much more common. They are known as NIPT or NIPD: Non Invasive Prenatal Diagnosis.

Did you know that from early in your pregnancy your baby’s DNA is present in your blood?? 

As the name suggests (the non invasive part) this is just a simple blood tests as by week 10 which is typically when these tests are done some of your baby’s DNA will be within your blood known as cfDNA (cell free DNA). Pretty cool stuff. 

What do these tests do and why would I get them done? 

This test is targeted to detect certain common genetic abnormalities where a particular Chromosome is present three times instead of the usual two. The most common example of this being Downs Syndrome. It will test for common incidence of this. Previously the only way this could be diagnosed was by Amniocentesis which is more invasive and carries some degree of risk. It can also tell you the sex of your baby!

How accurate is it? 

It is pretty damn good, however there is a very small incidence of false positives which will then need further investigation. If NIPT is positive then this will be confirmed and double checked by your doctor and an Amniocentesis will be recommended.

Next up: not for everyone but good to know: Pre implantation Genetic Diagnosis:

This is a more specialised, complex and in depth topic that is not relevant to everyone. Essentially however, this is for couples who have a known genetic risk. So either those who have flagged a risk factor in CarrierMatch or where one or both partner has a known genetic condition or those who have a close family member with a genetic condition. This test is targeted genetic testing of embryos for specific conditions and in order to get this done you will need to see a specialist and get a referral. This can include people who have the breast cancer gene BRACA1&2.

Bottom line on genetic testing:

It’s pretty darn cool how far science has come and what we can now see. However, as always it is not totally straight forward and these are all very personal choices. There is a fine (and often individual) line when it comes to knowledge being power and knowledge causing stress. Nevertheless we hope this little crash course has helped you figure out what is right for your own situation.

For more info check out one of the leading clinics on Genetic Testing: The Centre for Reproductive & Genetic Health. Click here for more.  


This article is for informational purposes only. This article is not, nor is it intended to be, a substitute for professional medical advice, diagnosis, or treatment and should never be relied upon for specific medical advice. The information on this website has been developed following years of personal research and from referenced and sourced medical research. Before making any changes we strongly recommend you consult a healthcare professional before you begin.

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