MaterniT21™ PLUS is a new test that offers women an alternative to traditional Down syndrome screening methods during pregnancy. Unlike amniocentesis and chorionic villi sampling (CVS), which are invasive tests, MaterniT21™ PLUS is a simple blood test that is non-invasive to you and your baby.
The testing can detect Down syndrome and other chromosome abnormalities, including trisomy 18, 13 and sex chromosome abnormalities. It has a higher detection rate and a lower false positive rate than first trimester screening, which is the most common non-invasive screening test in pregnancy today.
A New Approach to Down Syndrome Testing
MaterniT21™ PLUS utilizes sequencing technology to identify DNA derived from fetal chromosomes. The technology is applied to the circulating cell-free DNA in maternal blood (i.e., fragments of DNA present in maternal blood that is not enclosed by a membrane). This DNA from chromosomes 13, 18, and 21 is quantified and when overrepresented, the likelihood of these chromosome problems is significantly increased.
The detection rate for Down syndrome has been estimated to approach 99.1%, with a false positive rate less than 0.2%. The detection rate for trisomy 18 is over 99.9%, with a 0.28% false positive rate. The detection rate for trisomy 13, based on a small study, is estimated to be 91.7%, with a 0.97% false positive rate.
Additionally, the lab is testing for sex chromosome anomalies with a combined detection rate of 96.2% with a false positive rate of 0.3%. These include: Turner syndrome, Klinefelter syndrome, Triple X syndrome and 47, XYY syndrome.
At this time, the technology has only been validated in a high-risk population, which includes 1) women over the age of 35 at delivery 2) presence of an ultrasound finding 3) a personal or family history of chromosome abnormalities and 4) abnormal screening (e.g., first trimester screening).
A negative result significantly reduces the risk of Down syndrome and other chromosome abnormalities, and therefore, reduces the number of unnecessary invasive tests like amniocentesis and CVS.