Tests in pregnancy
Non-invasive prenatal testing (NIPT)
We offer NIPT via The Doctors Laboratory and can do the test in the comfort of your own home.
What is NIPT?
NIPT is a screening test that assesses the likelihood of a baby having one of the following chromosomal conditions:
- Trisomy 21 (Down’s syndrome)
- Trisomy 13 (Patau’s syndrome)
- Trisomy 18 (Edward’s syndrome)
There is the option to add sex chromosome aneuploidy screening which can assess the likelihood of the following, although this screening is deemed reliable it is not as accurate as the screening for trisomies 21, 13 and 18:
- Turner’s syndrome
- Klinefelter syndrome
- Other sex chromosome abnormalities
The NIPT can also assess fetal sex (optional extra, free of charge).
The NIPT is not a diagnostic test. What this means is that if you receive a high probability result, we would recommend referral to your local NHS team to discuss further diagnostic testing. It only screens for chromosomal abnormalities and does not screen for genetic conditions.
How is the test performed?
The NIPT involves taking a single blood sample from the mother or birthing person . This is then sent to and processed by The Doctor’s Laboratory in London. You must be at least 10 weeks pregnant and an ultrasound is required prior to the test to assess dates, viability and the presence of twins.
How does it work?
There are small fragments of DNA in a mother or birthing person’s blood that come from the placenta. TDL uses an NIPT assay called Veriseq v2 manufactured by Illumina and processed in their London laboratory. The assay analyses the proportions of the DNA fragments that come from specific chromosomes. If a certain proportion is too high or low this indicates that there may be a chromosome condition involving the placenta and possibly the baby.
How accurate is the test?
NIPT provides fewer false positives and false negative results for trisomy 21, 18 and 13 than the conventional first trimester combined screening or quadruple test which are routinely offered by the NHS . Combined screening will detect 82% of babies with a trisomy condition, compared to the NIPT which will detect >99% of babies with a trisomy condition.
When will I receive the results?
Results are ready in 3-5 business days following receipt in the laboratory and are usually sent to your healthcare provider. For each condition requested on the form, the report will indicate a high or low probability of the condition being present. We will discuss your results with you and make appropriate recommendations for referral for further testing, usually by liaising with your local NHS maternity trust. It is worth thinking about the implications of receiving a high probability result and what you may do in that situation before having the test.
Does a low probability mean that the baby is unaffected by a chromosomal condition?
No, there is always the chance with any screening test of receiving a ‘false negative’ result. However the likelihood of this happening with the NIPT is much lower than the conventional screening methods offered routinely on the NHS.
Does a high probability mean that the baby is definitely affected by a chromosomal condition?
Not necessarily, but it does mean there is a higher chance the baby may have a chromosomal condition. You will be offered further diagnostic tests to assess the chromosomes directly. The two diagnostic tests available are amniocentesis and chorionic villus sampling (CVS) and would be discussed with you by an NHS specialist.
Can I have the NIPT if I’m having twins?
Yes, however it is not suitable in the cases of a vanishing twin or demised twin. High probability results apply to one or both twins. If you’ve opted to find out the sex, a male result applies to one or both babies and a female result applies to both babies. The sex chromosome aneuploidy screening is not able to be performed for a twin pregnancy.
Will I always get a result?
According to TDL, two out of 100 women and birthing people will require a repeat test. There is no extra charge if the test needs repeating. In rare cases it is not possible to obtain a result, which is usually due to the complex biology of pregnancy. You will not be charged if the NIPT is unable to provide you with a result for the three most common chromosomal conditions (trisomy 21, 18 and 13).
Is the test available on the NHS?
NIPT is not routinely offered on the NHS. It is only offered to women and birthing people as a follow-up test if they have received a high chance result (>1:150) from a previous NHS screening test, such as the combined screening test or the quadruple test.
How much does it cost?
The cost of the test is £350.
Further information:
Antenatal Results and Choices (ARC)
Private blood tests
There are several blood screening tests that are offered routinely by the NHS during pregnancy. At a minimum you will be offered several blood tests at your initial booking appointment and then two repeat blood tests at 28 weeks. It is always your choice if you would like to have these bloods tests. Some women and birthing people choose to have these bloods taken privately and we can facilitate this via The Doctor’s Laboratory.
We can offer the following blood screening tests:
- Full blood count
- Blood group & rhesus status
- Antibodies
- HIV status
- Syphilis status
- Hepatitis B status
- Sickle cell, thalassaemia & other haemoglobin disorders
- Rubella status
- Chicken pox immunity status (Varicella zoster)
If there are any concerns with any of the blood tests results, we would recommend referral to an NHS obstetrician and/or your GP. Prices for these blood tests vary – please get in touch if you would like to find out more.