PrenatalSEQ Test
Genetic testing during pregnancy
- Trisomy 21 (Down syndrome)
- Trisomy 18 (Edwards syndrome)
- Trisomy 13 (Patau syndrome)
- Sex Chromosomal Disorders (Optional)
- Fetal Sex Determination (Optional)
About PrenatalSEQ Test
DNA from the fetus circulates in the mother’s blood. Cell-free DNA (cfDNA) results from the natural breakdown of fetal cells (presumed to be mostly placental) and clears from the maternal system within hours of giving birth.
During a pregnancy, cfDNA can be tested to give the most accurate screening approach in estimating the risk of a fetus having a common chromosome condition sometimes called a trisomy. This occurs when there are three copies of a particular chromosome instead of the expected two. The test looks to detect the following conditions:
- Trisomy 21 is the most common trisomy at the time of birth. Also called Down syndrome, it is associated with moderate to severe intellectual disabilities and may also lead to digestive disease, congenital heart defects and other malformations.
- Trisomy 18 (Edwards syndrome) and Trisomy 13 (Patau syndrome) are associated with a high rate of miscarriage. These babies are born with severe brain abnormalities and often have congenital heart defects as well as other birth defects. Most affected individuals die before or soon after birth, and very few survive beyond the first year of life.
- Sex chromosome conditions occur when there is a missing, extra, or incomplete copy of the X or Y chromosomes. The NIPT test with sex chromosome aneuploidy panel option can assess risk for XXX, XYY, XXY (Klinefelter syndrome), and a missing X chromosome in a girl (Turner syndrome).
In addition, NIPT can assess fetal sex. This is optional (no additional cost).
NIPT does not screen for non-chromosome disorders, familial mutations, malformations, fetal growth or fetal viability.
Risk
The testing is non-invasive: it involves taking a blood sample from the mother. The pregnancy is not put at risk of miscarriage, or from other adverse outcomes that are associated with invasive testing procedures such as amniocentesis.
Accuracy
NIPT provides fewer false-positive and false-negative results than combined first trimester screening for trisomy 21, 18 and 13.
It is important to note that NIPT is a screening test and does not provide a definitive genetic diagnosis, as NIPT cannot differentiate potential chromosome differences between the placenta and fetus. A definitive genetic diagnosis of the fetus requires cytogenetic analysis of either amniotic fluid or chorionic villus sampling (CVS).
Who can have the test?
NIPT can be ordered by healthcare professionals for women with pregnancies of at least 10 weeks’ gestational age. This test can be requested for any singleton or twin pregnancy, including those conceived naturally or by IVF using the patient’s own egg or a donor egg.
Note that, in twin pregnancies, sex chromosome (X and Y) analysis can determine fetal sex but not sex chromosome conditions. This test is not suitable in the case of a vanishing twin. The sex of twins will be reported as one result. If male, one or both of the twins will be male. If female, both twins will be female.
The test does not assess risk for mosaicism, partial trisomies or translocations.
