I heard there’s a new prenatal blood test for Down syndrome and other problems. What’s the deal?
Non-invasive prenatal testing (NIPT) is a relatively new blood test taken in the first trimester of pregnancy to determine a fetus’s risk for chromosomal abnormalities, including Down syndrome (trisomy 21), trisomy 13 and 18 and sex chromosome abnormalities, such as Turner syndrome.
The test is highly accurate -- it has a 98% accurate detection rate and very low rate of false positives – but it’s a screening test, not a diagnostic test. In other words, NIPT can’t tell you, definitively, whether or not your baby has Down syndrome or another chromosomal abnormality. It can only tell you whether there’s a high probability or a low probability of one. If the test says there’s a high probability, you may want additional, invasive testing, such as an amniocentesis or chorionic villus sampling to help confirm or deny the diagnosis. Some moms-to-be prefer have do the blood test before deciding to have an amnio or CVS because it doesn’t pose any risk to the baby-to-be, and those others do have risks associated with them.
If you’re saying, “I’m in!” hold on a sec. The test, which can be performed around 10 weeks of pregnancy, isn’t for all pregnant women. The American College of Obstetricians and Gynecologists (ACOG) doesn’t recommend NIPT as a first-line screening test for young women with low-risk pregnancies. But if you’re over 35 (because the risk of fetal chromosomal abnormalities increases with the mom-to-be’s age) or at increased risk of carrying a baby with an abnormality due to family history, it will likely be offered to you. Note that the test shouldn’t be used in twins and other multiples pregnancies, since there’s been limited research on how it works with multiples so far.
Talk to your doctor or midwife if you’re considering NIPT, to find out if you’re a candidate. If so, only you can decide whether you should get the test. For even more information, you can request a referral to a genetics counselor before making prenatal testing decisions. A genetics counselor can help you evaluate your personal risk factors and risk tolerance to help you make the right choices for your family.
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