NIPT (Non-Invasive Prenatal Test): Ultrasound Scan and Blood Test

No – you cannot have a NIPT test if you

• are carrying more than two babies
• currently have active malignant cancer
• are currently undergoing radiotherapy or chemotherapy
• are carrying a pregnancy with fetal demise
• have a history of organ transplant
• have mosaicism or maternal aneuploidy, which are rare maternal biological conditions
• have received a transfusion of heterologus cells in the last 12 months

The Warwick Evidence Systematic Review of the performance of NIPT found that the negative predictive value (NPV) of NIPT was 99.9%. The NPV tells you how likely it is that a low probability NIPT result is correct. This means that if you get a result that shows a low probability of the chromosomal conditions you can be fairly certain you do not have a fetus with any of the conditions.

The positive predictive value (PPV), which shows how likely it is that a high probably NIPT result is correct, varies for each condition tested:

• 82% for Down’s Syndrome (known as Trisomy 21)
• 49% for Patau’s Syndrome (known as Trisomy 13)
• 37% for Edwards' Syndrome (known as Trisomy 18)

A high probability result does not definitively confirm the presence of one of the conditions and further testing is required.

The NIPT test will detect 99% of pregnancies where a high probability of Down's Syndrome, Edward’s Syndrome or Patau’s Syndrome is present.

Results can also be inconclusive, which happens in less than 1% of cases. This is usually because the proportion of fetal DNA present in the sample is not high enough to give an accurate result. The test may be repeated with the hope that the fetal DNA levels will have increased due to the increased gestation. In some rare cases however, the fetal DNA is naturally low and in these instances a result cannot be yielded.

The NIPT is more accurate than the first trimester combined test or second trimester quadruple test for estimating the chance that the baby has Down's Syndrome. The false positive rates are 0.01% for Downs Syndrome, 0.01% for Edwards' Syndrome and 0.01% for Patau's Syndrome. Conventional screening tests can miss 15% or more of Down’s Syndrome pregnancies.

cfDNA is short for ‘circulating free DNA’. Fetal cfDNA is the circulating free DNA from your fetus in a maternal blood sample. The proportion of cfDNA in maternal blood that comes from the placenta is known as the fetal fraction.

The fetal fraction must be above 1.4%, which typically occurs around the tenth week of pregnancy. Low fetal fractions can mean the NIPT test can’t be done, or create a false negative result. Reasons for low fetal fractions include testing too early in the pregnancy, sampling errors, maternal obesity, and fetal abnormality.

An ultrasound Nuchal Translucency (NT) measurement (which measures the thickness of the fluid at the back of the baby's neck) when combined with a blood test and other maternal information provides an indication of the likelihood of a baby being born with Down’s Syndrome.

NIPT directly analyses the cell-free fetal DNA circulating in the pregnant mother's blood to detect the presence (or absence) of Down’s Syndrome, Edward’s Syndrome and Patau’s Syndrome.

The detection rate for NIPT is among the highest available for this type of antenatal screening and is recommended by the International Society of Prenatal Diagnosis (ISPD).

Yes, but not for triplets or higher multiple pregnancies. If one of the fetuses is no longer viable, the Harmony NIPT test cannot be performed.

We’ll take a new sample at no extra cost. There is a 0.2% failure rate for the overall test.

Yes, because the relative proportion of cell-free fetal DNA is reduced in people with a high BMI as they have more of their own cell-free DNA circulating in their blood. This may increase the chance of getting an inconclusive result.

No, we do not offer this. A microdeletion is the absence of a small piece of chromosome and is named by the area of the chromosome that is absent. Due to a lack of research into the reliability of this test, we do not offer it.

We do not offer this type of screening to evaluate the X and Y chromosomes. This is due to a lack of research currently available into the accuracy and detection rates of this test.

On rare occasions we are unable to complete the primary purpose of a scan. For pregnancy scans, this may be due to your baby being in a difficult position, or something else such as overlying bowel gas which can obscure the ultrasound image. If this happens, we’ll book you a free of charge rescan so we can try again! The primary purpose is outlined on each scan webpage.

As healthcare professionals the health and wellbeing of you and your baby is our priority. There may be occasions when we need to discuss unexpected findings or bad news. If this happens during your scan, our team will ensure you receive the best possible compassionate care delivered to you as sensitively as possible.  

We will also recommend your next steps. With your consent, we can contact the local early pregnancy unit or midwife on your behalf where possible. For general health scans, we can email our report and supporting images to your GP.  

If after your scan you become concerned about the scan itself or your images and video clips, just call the clinic where you had your scan to discuss any concerns. If the clinic is closed, contact our head office who will be more than happy to help with your query.

Absolutely! Every scan at Ultrasound Direct is performed by a fully qualified sonographer whose primary interest is your health. All our sonographers are fully trained and appropriately qualified to perform ultrasound scans. Many of our team also work in the NHS locally.

All our sonographers are registered with the Health and Care Professions Council and/or the Register of Clinical Technologists and follow the latest safety guidelines.

We are also registered with the Care Quality Commission, an independent regulator, to make sure you always receive the highest possible standards of care. 

All our sonographers who take blood for blood tests are phlebotomy trained.

If you are experiencing pain or bleeding, go directly to your local A&E or contact your midwife – do not book an ultrasound scan. This is because you may be experiencing a medical emergency and waiting for a scan will cause a potentially harmful delay.

Research suggests that there are no known risks to our method of ultrasound scanning. Scans are painless (although an internal scan may be slightly uncomfortable) and have no known side effects. Ultrasound scans do not use any form of ionising radiation, unlike other diagnostic imaging services such as x-rays.

 We follow the British Medical Ultrasound Society’s guidance for the safe use of diagnostic ultrasound equipment.

 During pregnancy scans, we can record your baby’s pulsebeat – this sounds very similar to the heartbeat, but is recorded in a different way. We record the pulsebeat by scanning blood flow through the umbilical cord, rather than recording the heartbeat by scanning the heart. This is because consistent ultrasound output in one place can have a heating effect, and we don’t want to put your baby at any level of risk. The fast-moving blood in the umbilical cord quickly disperses any potential heating effect.

Visit our FAQs page for any further questions you may have.