It is now possible to be screened for Down’s syndrome and certain other chromosomal abnormalities based solely on a blood test taken from the pregnant woman (NIFTY). This test analyses the foetal hereditary genes which circulate freely in the mother’s bloodstream (known as ffDNA).
It is currently possible to test for trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome) and trisomy 13 (Patau syndrome), as well as X and Y chromosomes, which determine the foetus’s gender. In all trisomies, there is an extra chromosome present and thus an increased amount of the specific DNA.
The test can be carried out after 10 completed weeks of gestation and there is no risk of causing a spontaneous abortion.
More than 200,000 of these tests have been carried out worldwide. The degree of certainty for detecting Down syndrome is over 99% and is slightly lower for other trisomies. The risk of a false positive screening is also very low, but for the time being, a placenta or amniotic fluid test is recommended if the screening detects the presence of an extra chromosome.
The screening is offered to pregnant women:
- Who would like to be screened for the chromosomal abnormalities mentioned without risking a spontaneous abortion (also in the case of twin pregnancies)
- Who have an increased risk of chromosomal abnormalities following a double test and a nuchal translucency scan
- Who have undergone IVF treatment
- Who have a higher risk purely because of their age
- Who are less suited to invasive diagnostic treatment due to an increased risk of abortion, infectious hepatitis or HIV (AIDS)
Results are normally available within 2–3 weeks.