Non-invasive pre-natal DNA test

Pre-natal tests can be taken from 10 weeks of pregnancy after the pregnancy date has been confirmed by a date scan. The 10-week scan would still be then followed by a 12 week (nuchal translucency) scan looking at the structural development of the baby. Results from prenatal testing are ready in around two weeks. Depending on the results, you may want to proceed with a more invasive test such as an amniocentesis.

NIPT can detect the above syndromes but NOT other physical defects such as spina bifida. The tests won’t show information on foetal growth, so you will still need to have your scheduled ultrasound scans during your pregnancy. The test is not intended for use in cases of multiple pregnancies.

The test involves analysing the cell-free DNA from the baby which is present in the mothers’ blood, making the test extremely accurate. Cell-free DNA (cfDNA) is DNA from the baby which circulates freely in the mother’s blood so can ,therefore, be accessed via a blood test. Unlike more invasive tests such as amniocentesis, where a needle is inserted into the womb to extract a sample of amniotic fluid, NIPT does not have an increased risk of miscarriage or other adverse outcomes.

The following trisomies can be tested for with a NIPT:

·       Trisomy 21

Also known as Down’s syndrome, trisomy 21 is the most common trisomy. Children born with Down’s syndrome often have heart disorders, digestive disorders, intellectual disabilities and other issues.

·       Trisomy 13 and Trisomy 18

Trisomy 18 (Edwards syndrome) and Trisomy 13 (Patau syndrome) are conditions which are associated with a high miscarriage rate. If babies with these conditions are carried to term then they are likely to be born with severe brain abnormalities, heart defects and other birth defects. Most babies affected by these syndromes won’t live beyond a year.

·       Y chromosome aneuploidy (XYY)

This chromosome disorder happens when the baby has an extra copy of chromosome Y. XYY can lead to mild disorders such as slight learning difficulties but these issues are so mild they are often not detected.