Non-invasive prenatal screening (NIPS) is a simple blood test that can be done from 10 weeks of pregnancy onwards to analyse the 23 chromosome pairs of a fetus’ genome. The screen is a way of determining if there is an increased chance that the fetus may have a genetic condition caused by a chromosome aneuploidy.
How does it work?
As the fetus grows, fragments of DNA are released from the placenta into the maternal bloodstream – this is called cell-free DNA (cfDNA). These fragments are free floating and not contained within cells (unlike most DNA, which is found inside a cell’s nucleus). Analysis of the cell-free DNA allows for screening of certain genetic conditions in the fetus.
The non-invasive prenatal screening service you’ll learn about on this website is called Illumiscreen and is the only NIPS service of its kind in Aotearoa New Zealand where your patient’s blood sample and personal / genetic information will remain in the country.
Conditions detected by Illumiscreen
Until recently, NIPS could only screen for the three most common pregnancy related conditions caused by a chromosomal aneuploidy.
- trisomy 21 (Down syndrome)
- trisomy 18 (Edward syndrome), and
- trisomy 13 (Patau syndrome).
Trisomy means that there is an extra chromosome present on the affected chromosome pair e.g. three chromosome 21s in Downs syndrome.
This type of prenatal screening has been available globally for over 30 years. The focus on just these three genetic conditions was due to limitations of the screen, not because they were the only known chromosomal conditions.
Today, Illumiscreen takes advantage of whole-genome sequencing (WGS) to deliver an expanded range of genetic conditions that can be screened.
This technology allows us to obtain a comprehensive view of all 23 chromosome pairs of the fetal genome while continuing to limit any risk to your patients. Illumiscreen can now also screen for:
- Rare autosomal aneuploidies (RAAs) – the most common RAAs detected in NIPS involve chromosomes 7, 16, 15, and 22.
- Partial duplications and deletions – partial deletion of a chromosome results in the loss of genetic material while duplication of chromosome results in the gain of extra copies of genetic material
- Copy number variants (CNVs) – this is when sections of the genome (the entire set of DNA instructions) are repeated and the number of repeats in the genome varies between individuals
With Illumiscreen, we will always screen all 23 chromosome pairs. The cost remains the same. See pricing for more information.
Having earlier insight into these chromosomal conditions may aid pregnancy and delivery decisions for you and your patient.
Medical Societies endorse NIPS for all pregnancies
As of October 2020, The American College of Obstetricians and Gynecologists (ACOG) and the Society for Maternal-Fetal Medicine (SMFM) endorsed NIPS as having the highest detection rate and lowest false positive rate of all prenatal screening options for the common aneuploidies, regardless of maternal age or baseline risk.
Not a diagnostic test
It is important to note that NIPS is a highly reliable non-invasive prenatal screening test – NIPS is not a diagnostic test. It will not provide a definite yes or no answer. The report will indicate if there is an increased chance the pregnancy has a chromosomal condition – see ‘Reading the report’. To confirm an increased chance result from this screen, a diagnostic test such as amniocentesis or chorionic callus sampling (CVS) is still necessary.
As a healthcare provider, you will need to discuss these procedures and their risks with your patient.
