Prenatal testing or screening can provide valuable information about your baby’s health and can identify whether your baby is more or less likely to have certain birth defects, many of which are genetic disorders.
These tests can be invasive or non-invasive in nature and they are usually offered during the first or second trimester of pregnancy. They include blood tests, a specific type of ultrasound and prenatal cell-free DNA screening.
What is Non-Invasive Prenatal Testing?
Non-invasive prenatal testing (NIPT), or sometimes called non-invasive prenatal screening (NIPS), is a method of determining the risk that the fetus will be born with certain genetic abnormalities. NIPT is a blood screening that the doctor may offer any time after 10 weeks gestation during your pregnancy.
The testing analyzes small fragments of DNA that are circulating in a pregnant woman’s blood. Unlike most DNA, which is found inside a cell’s nucleus, these fragments are free-floating and not within cells, and so are called cell-free DNA.
During pregnancy, the mother’s bloodstream contains a mix of cell-free DNA that comes from her cells and cells from the placenta. The placenta is tissue in the uterus that links the fetus and the mother’s blood supply. These cells are shed into the mother’s bloodstream throughout pregnancy.
The DNA in placental cells is usually identical to the DNA of the fetus. Analyzing cell-free DNA from the placenta provides an opportunity for early detection of certain genetic abnormalities without harming the fetus.
Why is NIPT considered non-invasive?
NIPT is considered non-invasive because it requires drawing blood only from a pregnant woman and does not pose any risk to the fetus. Essentially, NIPT is a screening test, which means that it will not give a definitive answer about whether or not a fetus has a genetic condition.
The test can only estimate whether the risk of having certain conditions is increased or decreased. In some cases, NIPT results indicate an increased risk for a genetic abnormality when the fetus is actually unaffected (false positive), or the results indicate a decreased risk for a genetic abnormality when the fetus is actually affected (false negative).
Because NIPT analyzes both fetal and maternal cell-free DNA, the test may detect a genetic condition in the mother.
What disorders can NIPT screen for?
NIPT is specific and doesn’t screen for every genetic condition. Most often it is used to look for chromosomal disorders that are caused by the presence of an extra or missing copy (aneuploidy) of a chromosome.
Specifically, the NIPT test primarily looks for:
- Down syndrome – trisomy 21, caused by an extra chromosome 21
- Edwards’ syndrome – trisomy 18, caused by an extra chromosome 18
- Patau syndrome – trisomy 13,- caused by an extra chromosome 13
- Klinefelter syndrome – caused by an additional X chromosome
- Turner syndrome – caused by a missing or partially missing X chromosome
These are all genetic conditions that can cause developmental delays and physical or mental defects. The accuracy of the test varies by disorder.
NIPT may include screening for additional chromosomal disorders that are caused by missing (deleted) or copied (duplicated) sections of a chromosome, and now it is beginning to be used to test for genetic disorders that are caused by changes (variants) in single genes. It is expected that NIPT will become available for many more genetic conditions.
How is NIPT test carried out?
There must be enough fetal cell-free DNA in the mother’s bloodstream to be able to identify fetal chromosome abnormalities. The proportion of cell-free DNA in maternal blood that comes from the placenta is known as the fetal fraction.
Generally, the fetal fraction must be above 4 percent, which typically occurs around the tenth week of pregnancy. Low fetal fractions can lead to an inability to perform the test or a false negative result.
To determine chromosomal aneuploidy, the most common method is to count all cell-free DNA fragments (both fetal and maternal). If the percentage of cell-free DNA fragments from each chromosome is as expected, then the fetus has a decreased risk of having a chromosomal condition (negative test result).
If the percentage of cell-free DNA fragments from a particular chromosome is more than expected, then the fetus has an increased likelihood of having a trisomy condition (positive test result). A positive screening result indicates that further testing (called diagnostic testing, because it is used to diagnose a disease) should be performed to confirm the result.
What are the benefits of NIPT?
- Non-Invasive Prenatal Testing (NIPT) can offer important clues about your developing baby’s health.
- The test may help you make informed healthcare decisions for your child, both while the baby is in the uterus and after birth
- Can tell you if you are at higher risk of having a baby with Down syndrome, Edwards’ syndrome, Patau syndrome, Klinefelter syndrome and Turner syndrome
- More than 99 percent accurate. False positives or false negatives rarely occur
- Fast (results within 10 working days)
- Affordable (inexpensive and only a tube of maternal blood is required)
- Safe because it is non-invasive, so poses no miscarriage risk or any other risk to the mother or the baby
Who should have Non-Invasive Prenatal Testing?
NIPT is a blood screening your doctor may offer any time after 10 weeks gestation during your pregnancy. Most often, your doctor will recommend the testing if you are at higher risk of carrying a child with a chromosomal abnormality.
You are more at risk if you are 35 or older, you have a prior pregnancy with a chromosomal condition or you have abnormal test results from other tests or screening. But you may also opt for the testing if you don’t have risk factors.
What can the NIPT results tell you?
We have explained above that NIPT works by analyzing cell-free DNA which is made up of maternal, fetal and placental DNA in your blood.
The testing also looks at the number of your baby’s sex chromosomes, which can tell you whether you’re having a boy or a girl. If it finds extra or missing sex chromosomes, that also may signal a genetic condition.
While the test is a safe way to screen for the three chromosomal conditions, it can’t tell you for sure whether your child will have one of them. It’s a non-diagnostic test.
If results indicate an increased risk for a genetic disorder, your doctor may encourage you to meet with a genetic counselor who can help you better understand your results and will discuss options for follow-up, including diagnostic tests and additional imaging.
So in a nutshell, NIPT can tell you:
- Risk of your baby for a genetic disorder
- Whether you need to go for a diagnostic test or see a genetic counselor
- Sex (gender) of your baby
Is NIPT available in Nigeria? (NIFTY and UNITY tests)
The NIPT test is carried out by Genomix, Nigeria’s leading provider of innovative healthcare and lifestyle solutions based on preventive genetic testing.
Genomix is based in Lagos. It enables pregnant women to have access to safe, accurate and affordable prenatal screening for the listed genetic conditions. It routinely carries out the NIFTY test which is its own patented NIPT test and conveniently screens for the above-listed genetic conditions caused by extra or missing genetic information in the baby’s DNA.
Genomix also carries out the UNITY test which is its patented highly accurate NIPT test that screens for cystic fibrosis, spinal muscular atrophy, sickle cell disease, alpha thalassemia, and beta-thalassemia.
The UNITY NIPT is the only test that screens mother and baby for the five commonly inherited conditions from a single tube of blood.