Non-Invasive Prenatal Test (NIPT)
What is it?
The Non-Invasive Prenatal Test (NIPT) screens for certain conditions caused by an abnormal number of chromosomes in a developing pregnancy. It also commonly known as a cell-free DNA (cfDNA) prenatal screen.
What is the difference between a screening test and a diagnostic test?
- Screening tests are used to estimate whether your developing pregnancy is at higher risk or lower risk of having a certain condition.
- Diagnostic tests can give a definite answer about certain conditions in the baby. These tests include an amniocentesis or chorionic villus sampling (CVS).
When can I do a NIPT?
Your doctor will do bloodwork to run the NIPT screen as early as 10 weeks of pregnancy and up until delivery.
Who can do a NIPT?
NIPT is available to anyone who is pregnant. Keep in mind, however, that NIPT has been shown to be less accurate if you are:
- Pregnant with twins or triplets
- Pregnant with a donor egg
- Pregnant and a gestational carrier
- Less than 10 weeks pregnant
- Taking certain blood thinners
How is it done?
A simple blood test on a pregnant woman is all that’s needed to do a NIPT. Some of the genetic material (DNA) from a developing pregnancy circulates in the mother’s bloodstream starting as early as 10 weeks and a blood sample will contain maternal DNA and DNA from the pregnancy. The blood sample is drawn in your doctors office and then analyzed in a special laboratory.
What are the risks associated with NIPT?
NIPT poses no physical risks for you or your baby. While it might cause some anxiety, it might also help you avoid the need for more invasive tests, treatment or monitoring during your pregnancy.
What does it screen for?
NIPT screens for common chromosomal trisomies. Trisomy means that there are three copies of a particular chromosome instead of the normal two copies. For instance, Trisomy 21 means that there are three copies of chromosome 21. NIPT can also provide information about the baby’s sex.
Major conditions screened for:
- Down Syndrome (Trisomy 21)
- Edwards Syndrome (Trisomy 18)
- Patau Syndrome (Trisomy 13)
- Sex chromosome abnormalities
Conditions not screened for:
- Problems that are detected by ultrasound, such as neural tube defects, heart defects, and abdominal wall defects.
- Many other chromosomal and genetic disorders.
What does a negative test result mean?
A negative NIPT result means that the test did not detect an abnormal number of chromosomes for the genetic conditions that were tested. This is a reassuring or normal test result.
A negative test result does not ensure an unaffected pregnancy, but it does significantly reduce that risk. For example, with a negative test results there is only a 1% chance that the pregnancy may be affected by Down Syndrome.
What does a positive test result mean?
A positive NIPT result means that the test detected an abnormal number of chromosomes for the genetic conditions that were tested. However, this does not necessarily mean that the baby is affected by this condition.
Any positive NIPT result should be discussed with your provider and/or a genetic counselor. You will likely be referred for a diagnostic test such as chorionic villus sampling (CVS) or amniocentesis.
I have a negative NIPT result – do I need any more testing?
NIPT is not a diagnostic test and screens for only the most common chromosomal abnormalities that can be found in early pregnancy. While a negative NIPT result is certainly reassuring, it does not guarantee that the pregnancy may not be affected by a genetic disorder. There are many syndromes or disorders such as Autism that cannot be screened for during pregnancy.
THE BOTTOM LINE:
- NIPT is a good screening test to detect common chromosomal disorders, but it does have limitations.
- This blood test is done at or after 10 weeks of pregnancy and there is no physical risk to mother or baby.
- A negative result does not rule out the possibility of having a baby with a chromosomal disorder or other disorders that NIPT does not screen for.
- A positive result can be followed up with a diagnostic test to determine if the baby is truly affected.