Non-Invasive Prenatal Test (NIPT) is a DNA test on maternal blood to screen for the most common fetal chromosome anomalies: Trisomy 21 (Down Syndrome), Trisomy 18 (Edwards Syndrome) and Trisomy 13 (Patau Syndrome).
- 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.
- 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. Please note, however, that sex chromosome (X and Y) analysis is not available for twin pregnancies. The test can be ordered for women with pregnancies of at least 10 weeks’ gestational age.
Although NIPT can be performed in every pregnancy, it is especially indicated:
- If the triple test or first-trimester screening indicates an increased risk for Down Syndrome, Trisomy 18 or Trisomy 13.
- Advanced maternal age.
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. Once the mother decides to have the test performed, she will be asked to sign a consent form and her blood sample can be taken from a vein in her arm.
Clinical studies have shown NIPT has exceptional accuracy for assessing fetal trisomy risk. A high risk result is indicative of a high risk for a trisomy. The test identifies in singleton pregnancies more than 99% of fetuses with Trisomy 21, 98% of fetuses with Trisomy 18, and 80% of fetuses with Trisomy 13, and 96% of fetuses with Turner Syndrome. X and Y analysis provides >99% accuracy for fetal sex.
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Aneuploidy is a condition in which there are missing or extra chromosomes. In a trisomy, there is an extra chromosome. In a monosomy, a chromosome is missing. Inherited disorders are caused by changes in genes called mutations. Inherited disorders include sickle cell disease,
cystic fibrosis, Tay–Sachs disease, and many others
- Prenatal screening tests: These tests can tell you the chances that your fetus has an aneuploidy and a few additional disorders. This FAQ focuses on these tests.
- Prenatal diagnostic tests: These tests can tell you whether your fetus actually has certain disorders. These tests are done on cells from the fetus or placenta obtained through amniocentesis or chorionic villus sampling (CVS).
Genetic screening tests:
- They include carrier screening and prenatal genetic screening tests:
- Carrier screening is done on parents (or those just thinking about becoming parents) using a blood sample or tissue sample swabbed from inside the cheek. These tests are used to find out whether a person carries a gene for certain inherited disorders. Carrier screening can be done before or during pregnancy.
- Prenatal genetic screening tests of the pregnant woman’s blood and findings from ultrasound exams can screen the fetus for aneuploidy; defects of the brain and spine called neural tube defects; and some defects of the abdomen, heart, and facial features. They include first-trimester screening, second-trimester screening, combined first- and second-trimester screening, and cell-free DNA testing.
First-trimester screening includes a test of the pregnant woman’s blood and an ultrasound exam. Both tests usually are performed together and are done between 10 weeks and 13 weeks of pregnancy:
- The blood test measures the level of two substances.
- The ultrasound exam, called a nuchal translucency screening, measures the thickness of a space at the back of the fetus’s neck. An abnormal measurement means there is an increased risk that the fetus has Down syndrome or another type of aneuploidy. It also is linked to physical defects of the heart, abdominal wall, and skeleton.
- The “quad” or “quadruple” blood test measures the levels of four different substances in your blood. The quad test screens for Down syndrome, trisomy 18, and neural tube defects. It is done between 15 weeks and 22 weeks of pregnancy.
- An ultrasound exam done between 18 weeks and 20 weeks of pregnancy checks for major physical defects in the brain and spine, facial features, abdomen, heart, and limbs.
Cell-free DNA testing:
Cell-free DNA is the small amount of DNA that is released from the placenta into a pregnant woman’s bloodstream. The cell-free DNA in a sample of a woman’s blood can be screened for Down syndrome, trisomy 13, trisomy 18, and problems with the number of sex chromosomes. A positive cell-free DNA test result should be followed by a diagnostic test with amniocentesis or CVS.
This test is non invasive but due to costs and some false positive rate is not offered to all patients.Discuss with our physicians about your specific risks and available testing.
- A positive screening test result for aneuploidy means that your fetus is at higher risk of having the disorder compared with the general population. It does not mean that your fetus definitely has the disorder.
- A negative result means that your fetus is at lower risk of having the disorder compared with the general population. It does not rule out the possibility that your fetus has the disorder.