Non-Invasive Prenatal Testing (NIPT) Factsheet
IntroductionNIPT, which analyzes cell-free fetal DNA circulating in maternal blood, is a new option in the prenatal screening and testing paradigm for trisomy 21 and a few other fetal chromosomal aneuploidies. (For more information about current screening/testing options, see Background.)
NIPT Test Characteristics
Genetic testing using cell-free fetal DNADNA from the fetus circulates in maternal blood. Unlike intact fetal cells in maternal blood, which can persist for years after a pregnancy, circulating cell-free fetal DNA (ccffDNA) results from the breakdown of fetal cells (mostly placental) and clears from the maternal system within hours. Fetal DNA detected during a pregnancy, therefore, represents DNA from the current fetus. Although only about 10-15% of the cell-free DNA circulating in maternal blood is from the fetus, it can be detected and measured. Quantitative differences in chromosome fragments in maternal blood can be used to distinguish fetuses affected with trisomy 21, and a few other fetal aneuplodies, from those that are not affected.
When NIPT is performedTesting can be done any time after 10 weeks; typically it is done between 10-22 weeks. Results can take a week or more.
Maternal indications for NIPTNIPT technologies have been validated in singleton pregnancies at high risk for trisomy 21 due to:
- advanced maternal age
- an abnormal serum screen
- personal or family history of aneuploidy
- abnormal ultrasound