WHAT IS NIPT?

NIPT is a term used for a method of genetic screening used in antenatal screening, used to screen circulating free DNA (cfDNA) which can be found in a sample of a mother’s blood. It examines DNA in the chromosomes that originate from a baby and with today’s technology it is used to identify the risk of whether you are at an increased risk of giving birth to a child with a genetic disorder. There are 2 chromosomes in a set and a person usually has 46 sets of chromosomes, 23 sets from the mother and 23 sets from the father. NIPT can detect where there are extra chromosomes ie with Downs Syndrome or only one of a set as with Turners Syndrome.

 

NIPT EXPLAINED

Non-invasive prenatal testing works by analysing the cell-free DNA (cfDNA) present in the maternal bloodstream.

CfDNA is made up of genetic material from both the mother and baby. NIPT can identify small changes in the amount of DNA derived from individual chromosomes, these occur when the pregnancy has an abnormal number of chromosomes (aneuploidy).

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WHY TEST?

Everyone has their own personal reason for performing NIPT. For some they do not know their biological family or there is a history of genetic disease within the family. For other parents it is due to a history of recurrent miscarriage or general pregnancy anxiety, for may it is purely for reassurance purposes. 

 

This safe method of screening is used to enhance the depth of testing without adding any risk to your baby and does not replace your routine NHS Antenatal Care. The NHS Combined Screening has a high false positive rate compared to NIPT testing, and if given a 'higher chance' result, you will be asked to undergo further 'invasive' testing, which is often a very worrying time for parents. 

 

According to NICE guidance, a NIPT Test is the next recommended step before moving to diagnostic testing by Chorionic Villus Sampling (CVS) or Amniocentesis. Because both of these are 'invasive 'methods they come with increased risk of miscarriage. Therefore, many parents opt straight for NIPT as the reliability and accuracy of this screening method is recognised as being superior to NHS combined screening.

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However, NIPT tests are NOT diagnostic tests and the results alone must never be used to make critical decisions, you should always consult your care provider to discuss your results and plan further care. 

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CAUSES OF GENETIC CONDITIONS

Humans have 23 pairs of chromosomes (for a total of 46 chromosomes) { One copy of each chromosome comes from the mother (egg); the other copy comes from the father (sperm).

• The first 22 pairs are called autosomes, and they are same in males and females

• The 23rd pair of chromosomes are called sex chromosomes.

Females have two copies of the X chromosome and males have one X and one Y chromosome. 

An abnormality in an embryo's chromosomal configuration may cause a specific syndrome to occur or may cause the pregnancy to miscarry. Sometimes embryos are created with too many or too few chromosomes—a condition known as aneuploidy. 

Aneuploidy is a major contributor to miscarriage, in vitro fertilization (IVF) failure, and various health conditions, including Down's syndrome. 

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WHO ARE NIPT TESTS SUITABLE FOR?

• NIPT tests are suitable for pregnant women from the 10th week of pregnancy.

• We have tests that are suitable for both single and twin pregnancies (including vanishing twin). Please note the NIPT test will analyse the chance of an affected result for the pregnancy, but will not be able to provide a twin-specific chance. 

• The test is suitable for pregnancies achieved by IVF techniques, including gamets donation.

• The test is suitable for surrogate pregnancies.

• Gender determination can only report if a Y chromosome is or is not present. It will not identify which twin or if both twins are male.

 

NIPT RESULTS

NIPT involves a quick blood sample from the arm, making it safe and easy for you and your baby. Your sample is then sent to a laboratory where a technician will look at the DNA in your blood for signs of genetic abnormalities. Once the result of your test is analysed the laboratory will determine whether you are placed in the LOWER or HIGHER chance category. This can be used to indicate whether further diagnostic testing should be taken to confirm the result. Result times can vary between 3-10 working days depending on the test chosen and the analysis method of the test. ALL P test results are delivered personally to you by a medical professional.

 

NIPT RESULTS & ACCURACY

Accuracy is dependent on the syndrome you are screening for. There is a very small chance the test will not detect an affected pregnancy. There is a small chance (around 0.3%) that the test will incorrectly show a positive result, in this instance we would always recommend diagnostic testing.

NIPT is more accurate than the first trimester NHS combined test or second trimester NHS quadruple test for estimating the risk of genetic disease. However, NIPT is a form of 'screening' and is not a diagnostic test. Amniocentesis or Chorionic Villus Sampling are the recommended tests which are diagnostic however, as these come with risks of miscarriage it is recommended to use the no risk NIPT test as the first step. Any concerns during pregnancy should always be discussed with your healthcare provider.​

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FACTORS THAT AFFECT RESULTS

Results that are reported as negative do not eliminate the possibility that the pregnancy has other chromosomal abnormalities, genetic conditions, or birth defects. There is a small possibility that the results might not reflect the chromosomes of the baby, but the chromosomal status of the mother or placenta (a situation known as “placental mosaicism”) or the presence of a tumour (as tumours often have an incorrect number of chromosomes in their cells). 

 

WHEN CAN NIPT TESTS BE PERFORMED?

PrenatalSAFE NIPT’s can be performed any time after 10 weeks — this is earlier than any other antenatal screening or diagnostic test. 

NHS antenatal screening; 

• Nuchal translucency scanning: between 11 and 13 weeks 

• CVS: 10 to 13 weeks 

• Quad screen: between 14 and 22 weeks

• Amniocentesis usually performed between 16 and 18 weeks & sometimes as early as 13 or 14 weeks or as late as 23 or 24 weeks

 

THE ACCURACY OF NIPT

NIPT tests create less false alarms than standard NHS first-trimester blood screenings (like first-trimester bloodwork or quad screening). Research has shown that NIPT is much more accurate than those same standard screenings in predicting the risk of chromosomal abnormalities. Because of the high rates of false 'positive' from NHS combined screening, many women are often referred to us from our NHS colleagues when they receive a 'higher chance' combined result. Some hospital offer NIPT privately themselves for a similar fee, however they do not include gender determination AND take much longer to report the results back to you. Contact us for further information on the test you have chosen.

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'HIGHER CHANCE' RESULTS

In the event of a 'higher chance' NIPT result we make a medical referral to your local fetal medicine team who will help you to decide the next steps forward, including whether to have a fully diagnostic test like Chorionic Villus Sampling (CVS) or amniocentesis (“amnio”). Both tests analyze a baby’s own genetic material, collected from the amniotic fluid or placenta to tell with 100 percent certainty whether a baby actually has a chromosome abnormality. However, these tests are invasive, which means they slightly increase the chance of miscarriage approx 2% for Chrorionic Villus Sampling (CVS) nationally ie. approximately 1 in every 50 women, and 1% increase for Amniocentesis, which is 1 in every 100 women who have the procedure. 

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WHEN IS NIPT NOT SUITABLE?

• NIPT is not suitable if you have been diagnosed with cancer or know that you have chromosomal abnormalities including Trisomy 13, 18 and 21. 

• NIPT cannot be performed if you have had an organ transplant or received stem cell therapy or immunotherapy within the last 12 months. 

• NIPT cannot be performed if you have had a blood transfusion with the last 3 months.

 

TWIN PREGNANCY & GENDER REPORTING

All Trimester tests can be performed with a pregnancy that began as a twin or has remained a twin pregnancy. As with all NIPT test providers, the status of each individual baby cannot be determined, therefore the result will reflect the entire pregnancy. The test can also only report the presence or absence of Y chromosome material (found only in males) but it will not be clear whether both twins are male or just one of them.

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POINTS TO CONSIDER

Results apply only to conditions tested.

A negative result means your pregnancy has a decreased chance of having a condition { In most cases, the condition is truly not present (true negative result) { Rarely, the condition may be present (false negative result)

A positive result means an increased chance of having the condition { In most cases, the condition is truly present (true positive result) { In some of these, the condition is not present (false positive result)

Since NIPT is a screening test, results should be taken into context of the overall pregnancy picture and positive results should always be confirmed prior to making pregnancy management decisions.

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WHAT IS A FAILED RESULT

This means that it has not been possible to produce a result.  In a small number of cases (less than 0.1%)* it is possible that there is not enough cFDNA from your baby present in your blood (Fetal Fraction) to produce the result. The laboratory will request a second sample at no additional cost. However, you may be asked to pay for the Phlebotomy appointment if one is required.
Please note: A failed test result will only be reported after comprehensive testing of your sample. * Dependent on the test you have chosen

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STOPPING THE CONTRACEPTIVE PILL TO START YOUR FAMILY?

Once stopped, gradually, the body's natural hormones will resume and begin regulating the menstrual cycle. Most people have their first period 2–4 weeks after coming off the pill. However, it can take up to 3 months for the natural menstrual cycle to fully re-establish itself.

 

PRE TEST PREPARATION

For the mother - It is recommended that the mother has her blood test before the father has the buccal swab. We recommend that you eat as normal but you can increase your fluid intake by drinking a pint of water an hour before your appointment. Until your test, please keep your arms warmly covered to help with blood flow. Do let us know beforehand if you have ever fainted during a blood test or had an allergic reaction to anything within a medical environment.

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PREPARATION FOR THE FATHER

It is recommended that the father refrains from eating, drinking, chewing gum, brushing teeth, or smoking for at least 30 minutes before sample collection. This is vital to obtain a usable sample for processing.

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