What is a prenatal DNA test?

What is a prenatal DNA test?

What is a prenatal DNA test?

Until relatively recently parents had to wait until the birth of their baby to find out the sex, the health, and sometimes the paternity of their child. However, DNA testing is becoming more and more accessible to individuals and analysis techniques are continually advancing. It is now possible to learn a significant amount of information about your baby by taking a DNA test before birth, from as soon as nine weeks into pregnancy.

Prenatal DNA testing can now tell you if you should prepare for the birth of either a little boy or girl. It can ensure that if your baby is likely to be born with a health problem, he or she immediately receives the best possible care. It can also determine the paternity of a child which can help to reduce stress during pregnancy, and allow parents to make care and visitation arrangements early on.

If you would like to find out whether your baby will be a boy or a girl, take a look at our prenatal sex testing providers. Or, if you would like to confirm the biological parentage of your child, check out our prenatal paternity testing providers.

Pregnancy DNA Test Expectations

Prenatal genetic testing can provide you with a range of information about your unborn child, from its sex to the likelihood that it will be born with a health problem. Before taking a prenatal DNA test though, it’s important to know exactly what information you’ll be provided with, and what you are or are not able to find out.

Prenatal Gender DNA Tests

Prenatal genetic testing can predict the sex of your baby from seven weeks into pregnancy. These tests look at the sex chromosomes (XX for girls and XY for boys) in the mother’s blood. The presence of Y chromosomes in the blood indicates that the baby is likely to be a boy. If there are only X chromosomes, then it is likely that the baby is a girl. Although these tests are estimated to be 95% accurate, the companies that offer this type of prenatal genetic testing are careful to point out that it is only a prediction, the same as an ultrasound. A major reason for this warning is that it’s very easy for any male family or friends to contaminate the blood sample by coming into contact with it or with the sample collection kit. Even having a male person in the room when carrying out the test risks contamination! So, if you choose to take a baby DNA test for gender, make sure you follow the instructions very carefully to ensure you get a result that’s as accurate as possible.

Prenatal DNA testing and ultrasounds can both predict the sex of your baby, but there are several differences between them in terms of what information they can provide you with, and in what circumstances. Firstly, a gender-determining baby DNA test can be carried out from as early as seven weeks into pregnancy, though it’s worth noting that companies usually only offer this service from around nine weeks. Either way, this is earlier than when most women have their first ultrasound scan which can be as late as 14 weeks into their pregnancy. In addition to predicting gender, ultrasounds can be used to assess the health and development of your baby, as well as your due date. Therefore, prenatal DNA testing isn’t a replacement for ultrasound scans, but it does offer advantages in terms of gender prediction.

One benefit of prenatal genetic testing is that it doesn’t rely on your baby being in the right position to accurately predict gender, whereas an ultrasound does. The mother’s weight can also affect the accuracy of gender prediction via ultrasound, but not when using a pregnancy DNA test. Fortunately, many companies offer free second tests if the first is inconclusive. Finally, although having twins restricts what a baby DNA test for gender can tell you, it can still predict gender earlier than an ultrasound can. Using a DNA test while pregnant with twins won’t be able to tell you if you’re having one boy and one girl, or if both of your babies will be boys, but it can tell you if you’re likely to have at least one boy or all girls. If you want to find out more about the science behind pregnancy DNA tests used in gender determination, take a look at our DNA testing during pregnancy article.

Prenatal Paternity DNA Tests

You can also take a DNA test before birth to deal with any doubts that you may have about the paternity of your child. This type of baby DNA test can tell you with up to 99.99% certainty whether the alleged father is the biological father of the baby. If it turns out that he’s not the biological father, then the DNA testing provider you’ve used will often allow you to test other potential fathers for free or at a reduced price

This type of prenatal genetic testing is usually offered from around nine weeks into pregnancy and can provide reassurance about who the biological father of your baby is. Some companies now also offer a baby DNA test for legal paternity issues. These are more expensive, but the results can be used as evidence in court. The difference between so called ‘peace of mind’ and legal DNA tests is explained in our article What is legal DNA testing?.

You can choose between non-invasive or invasive prenatal DNA testing – non-invasive tests require a blood sample and invasive tests require chorionic villus sampling (CVS) and/or amniocentesis. Both types of invasive test involve taking samples from the environment in which your baby is developing.

It’s important to note that invasive prenatal DNA testing involves a risk of miscarriage, and in practice is not offered by many providers. It should also be said that doctors have a right to refuse to carry out invasive procedures for this reason.

Bear in mind that whether you want a non-invasive or invasive test, some companies will require you to organise having the samples taken. Further information about non-invasive and invasive prenatal DNA testing can be found in our article, DNA testing during pregnancy.

Prenatal Health Screening DNA Tests

Although thousands of diseases are thought to be genetically passed from parents to children, only Down’s syndrome (also called Trisomy 21), Edward’s syndrome (Trisomy 18) and Patau’s syndrome (Trisomy 13) are tested for by the NHS. This is done through a free blood test offered 10-14 weeks into pregnancy, and it works by looking at the proteins and hormones associated to the conditions.

However, if you wanted to screen for genetic conditions in addition to Down’s, Edward’s and Patau’s syndrome, perhaps due to your family history, a baby DNA test before birth can do this by identifying extra sex chromosomes and deletions – Counsyl is one such company that offers this.

Studies have shown that testing the baby’s DNA can more accurately predict whether he or she will be born with one of these conditions. In fact, it has been estimated that the current blood test for Down’s syndrome predicts the condition with 85-90% certainty which includes 2.5% of ‘false positive’ results – false positives are an important issue because in 90% of cases a positive prediction leads to the termination of the pregnancy. However, pregnancy DNA tests are 99% accurate and are thought to result in fewer false positives.

The NHS has recently announced that it will start offering prenatal DNA testing for Down’s syndrome from 2018, and this may eventually replace screening techniques for all conditions currently covered by the standard blood test.

What’s involved in a pregnancy DNA test?

Nowadays, the vast majority of prenatal genetic testing is non-invasive and simply requires a blood sample. DNA tests before birth for the baby’s gender only require a small blood sample which can be obtained via a ‘finger prick’ device (similar to those used by diabetes patients). The DNA test kit you’ll receive after ordering will usually contain this device which will allow you to prick your finger in a sterile and safe way, so that you can collect the blood sample from home.

All you have to do is place the drop of blood on the collection card provided, and leave it to dry for about half an hour. This should be done in a room with moderate temperature and light intensity, as both factors can affect the integrity of the sample. Once dry, you will be able to put the sample into an envelope, which should be provided in your kit, and send it back to the lab. Most providers will deliver your results within eight days of your sample reaching the lab, but you can often pay for an express service to get the results in half the time.

Larger blood samples, required when taking either a paternity DNA test before birth or a health screening DNA test before birth, must be drawn by a trained medical professional. If you’ve established that it’s your responsibility to arrange the sample collection, it’s a good idea to do this before ordering your pregnancy DNA test to make sure there are no unexpected delays.

Some providers such as DNA Worldwide offer to organise the sample collection appointments for you, and may even allow you to have the blood drawn from home. However, this isn’t always the case so make sure you check!

When you order a pregnancy DNA test for paternity, even though you can’t draw the blood yourself, the test kit you receive will still contain the equipment needed to store your samples – you should take this to the clinic where you are having the procedure. The kit equipment will include (normally two) collection tubes for the mother’s blood samples, swabs to take the alleged fathers’ saliva samples, instructions, and often return packaging suitable for the transport of biological samples.

For health screening DNA tests before birth, the test kits are often sent directly to your healthcare provider rather than to you personally, even if you ordered it independently of your doctor. These test kits will be similar to those for paternity, but they won’t contain swabs for the alleged fathers’ samples.

In all three cases, once your samples have reached the lab, providers will deliver the results in one to two weeks.

Involvement of medical professionals

As well as the requirement for a trained medical professional to take a larger blood sample, there are other aspects of taking a DNA test during pregnancy that should involve them; prenatal DNA testing for health screening for example. This is partly because of the mental and emotional effects of finding out that your baby may be born with a serious and/or lifelong health condition. For this reason, most companies offering these types of test will provide support once the results have been produced. This support is often termed ‘genetic counselling’ and isn’t unique to DNA testing while pregnant. Companies hire or form close partnerships with genetic counsellors and sometimes, with your permission, your doctor. They will help you to fully understand your results, to possibly organise further testing and if necessary, discuss your options in terms of how you want the pregnancy to progress. Our article ‘What are the implications of genetic testing?’ covers the broader issues associated with the impact of taking a DNA test should you wish to find out more.

Prenatal DNA tests for health screening can be ordered via a doctor. This usually means that you’ll have a consultation beforehand to make sure the test is suitable and necessary. Although this may seem like unnecessary bureaucracy, it may prevent you from taking a test that isn’t going to be helpful, or from searching for answers that your doctor may already have.

Discreet prenatal paternity tests

Several companies offer so-called ‘discreet’ prenatal paternity tests. These offer answers relating to the paternity of your child using items (e.g. toothbrushes) that contain the alleged father’s DNA, allowing the test to be undertaken without his knowledge. There are several understandable reasons why you may want to do this; to avoid unnecessary upset, or perhaps if someone has refused to cooperate. However, the Human Tissue Act 2004 states that it is a criminal offence to possess someone’s DNA with the intention of testing it without their consent. This isn’t something that is legislated for in the US which is why many providers can offer this option, but be aware that even if you use a provider based in the US, the law still applies to UK residents.

rebecca wain

22 June 2018

please can you help me find out how much it will cost to have the paternity test done whilst 16weeks minimum please and the best company to go to that is 100% proof safe and the testing 100% positive or as close to asap many thanks

    Hi Rebecca,

    Thank you for your recent comment.

    If you visit this page, you can read the reviews to see which test is best for you: https://dnatestingchoice.com/prenatal-paternity-testing

    Alternatively, if you email me directly at hseldon@dnatestingchoice.com, I will recommend you some of the companies we've worked with and trust.

    I hope this is helpful!

    Kind regards,


    Harriet Seldon | Services Team

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