Non-invasive Prenatal test (NIPT)

Screening tests are different to diagnostic tests. Diagnostic tests are often more invasive. However they confirm for certain if the result is positive.

During pregnancy, some of the baby’s DNA passes into your bloodstream. The non-invasive prenatal test analyses the genetic information contained in this DNA. It’s used to screen for a number of genetic conditions. The test is particularly sensitive to Down syndrome.

An NIPT is done from 10 weeks into the pregnancy. Before the test you will be asked to give consent.

What does it test for?

The NIPT is a safe and very effective way of screening for certain conditions. These include:

• Down syndrome (also called trisomy 21)
• Edwards syndrome (trisomy 18)
• Patau syndrome (trisomy 13)
• Turner syndrome

Some laboratories also test the sex of your baby and look for differences with the sex chromosomes.

The test identifies many chromosomal anomalies. It doesn’t screen for genetic disorders such as:

• cystic fibrosis
• thalassaemia
• sickle cell anaemia

Screening will tell you how likely it is that your baby has a chromosomal difference. The only way of knowing for sure is to have a diagnostic test such as:

• chorionic villus sampling (CVS)
• amniocentesis

Should I have an NIPT?

The NIPT is very sensitive. It picks up more than 99% of cases of Down syndrome. But it is a screening test rather than a diagnostic test.

It can tell you whether there is an increased chance of having a baby with a genetic condition. It doesn’t give you a definitive answer. For some parents, information from screening tests can help them decide about whether to have diagnostic testing.

You might choose to have an NIPT test if:

Your first trimester combined screening test shows you have an increased chance of having a baby with Down syndrome (this test combines results from a blood test at 10 to 12 weeks and an ultrasound at 11 to 13 weeks).

• You did not have the first trimester combined screening test because it was too late or the test wasn’t available in your area.
• You want to understand your chance of having a baby with Down syndrome before considering diagnostic tests such as amniocentesis or CVS.
• You have an increased chance of having a baby with Down syndrome because you are older or you or your partner already have a baby with Down syndrome or another genetic condition.

It’s a good idea to consider genetic counseling before you have an NIPT to help you make an informed decision. It’s important to understand the risks and benefits of having the test.

Genetic counselors can:

• review your family and medical history
• give you information about genetic tests
• help you learn about how the condition is inherited
• offer advice on support services

If your pregnancy is affected by a genetic condition, your genetic counsellor can:

• help support you
• help you understand what the results mean for you and your family

What can I expect from my NIPT results?

It can take up to 2 weeks to get the result of your NIPT.

If your NIPT result shows that your baby is likely to have a chromosomal difference, a diagnostic test such as: CVS or amniocentesis can confirm the result.

You should discuss your options with your doctor, midwife or genetic counselor.