Here’s What Noninvasive Prenatal Tests Actually Screen for
There’s no shortage of emotions that come with being pregnant. One minute you’re overjoyed, the next you’re crying over commercials—thanks, hormones!—and many women might even feel a bit anxious about baby’s health. Luckily, over the next 40 weeks, you’ll be spending plenty of time at your doctor’s office checking up on that last one. At your first prenatal visit, your ob-gyn will likely run through an overview of testing options that’ll help keep tabs on your health and the health of your baby. If genetic conditions are a concern, cell-free fetal DNA testing, also known as noninvasive prenatal testing ( NIPT), is an elective test you might want to consider.
NIPT is a simple genetic screening that analyzes fragments of baby’s DNA circulating in your blood to assess the genetic health risks of your pregnancy. Since it can be done as soon as 10 weeks, it’s a good way to look for any possible chromosomal abnormalities early on. It can determine whether baby is at an increased risk of certain genetic conditions (and, as a bonus, can even tell you baby’s sex). And because it’s a simple blood test, it doesn’t present any risks to your pregnancy that diagnostic tests like amniocentesis and chorionic villus sampling do. While NIPT is still relatively new, the American College of Obstetricians and Gynecologists (ACOG) recommends it should be discussed and offered as an option to all women. Check whether your insurance plan covers it, though—you may have to pay out of pocket.
NIPT isn’t diagnostic, meaning it can’t definitively tell you whether baby has a certain condition or not. However, it can give you an accurate idea of baby’s genetic health so you can discuss options and next steps with your doctor, like getting a diagnostic test for confirmation.
While you may not have heard of some of the genetic conditions on this list, chances are you’re familiar with Down syndrome. People with the condition—which is caused by an extra copy of chromosome 21—experience mild to moderate learning difficulties and have physical differences like heart defects, hearing problems, thyroid problems and an upward slant to the eyes. However, many people with Down syndrome can hold jobs, live independently with support, and have a good quality of life. According to a recent study, NIPT can accurately detect 99.2 percent of cases, and has significantly lower false positive rates and higher positive predictive values than standard first trimester screening tests.
Edwards and Pateau Syndromes
Two lesser-known and very severe conditions are Edwards syndrome, aka Trisomy 18, and Patau syndrome, aka Trisomy 13. These are caused by extra copies of chromosomes 18 and 13, respectively. Only about 10 percent of babies diagnosed with these conditions will reach their first birthdays, and those who survive have severe physical and cognitive impairments.
Sex Chromosome Conditions
You probably learned in biology that females typically have two X chromosomes and males typically have one X and one Y. However, when there’s an extra or missing X or Y chromosome, it can cause a genetic condition that otherwise might not be obvious at birth. This difference can result in a person having a higher chance of difficulty in school, behavioral issues or infertility.
If you screen positive for any of these genetic conditions, your doctor will likely recommend a more invasive diagnostic test that’ll analyze a sample of baby’s genetic material to determine whether baby actually has the condition. This is typically done via chorionic villus sampling (CVS), where your doctor takes a sample of cells from a part of your placenta—usually between weeks 10 and 13—or an amniocentesis, where a sample of your amniotic fluid is removed and tested between weeks 15 and 20.
Again, NIPT is a screening test and doesn’t 100 percent confirm or eliminate the chances that your baby will have a genetic condition. However, it can give you peace of mind and help you become better informed and prepared for what’s to come. Talk to your doctor if you’re interested in getting NIPT; they can guide you from there.
Published February 2019