A non-invasive prenatal test (NIPT) can detect the most common chromosomal abnormalities (trisomies 21, 18, and 13, and depending on the test method, sex chromosome aneuploidies as well as certain microdeletions) through modern high-throughput methods () performed on cell-free DNA of placental origin. This DNA is present in maternal blood or plasma during pregnancy. This significantly reduces the low procedural risk associated with invasive prenatal diagnostics for these specific questions. However, positive results should always be confirmed by amniocentesis, as false-positive and false-negative results are possible due to, for example, fetoplacental mosaicism.

All test methods require a sufficiently high fraction of placental DNA against the background of maternal DNA. The foetal fraction increases as pregnancy progresses but can be very low (< 4%) in some pregnant individuals. To ensure a sufficiently high foetal fraction for most individuals being tested, blood collection should not occur before the 10th week of pregnancy.

The tests currently available in Germany have been validated on high-risk populations, such as those with advanced maternal age or abnormal first-trimester screening results. For individuals without increased risk (e.g., pregnant individuals with unremarkable family histories or younger pregnant individuals), there is currently a lack of reliable data. Despite high sensitivity and specificity, false-positive and false-negative results can occur, which is why these tests are not currently considered diagnostic. Therefore, it is recommended that any abnormal findings be confirmed through diagnostic amniocentesis.

After genetic counselling (NIPT is regulated under the Genetic Diagnostics Act), 10-20 mL of blood are collected from the pregnant individual using specialized BCT tubes. After separating the blood plasma, the cell-free DNA from the placenta and mother is enriched and then quantitatively and/or qualitatively analysed using NGS.