A positive result on a prenatal screening test for Down syndrome does not mean your baby has Down syndrome. It means the screening detected a higher-than-average risk, and the next step is deciding whether to pursue a diagnostic test that can give you a definitive answer. For the most common screening test, cell-free DNA screening (often called NIPT), a positive result for Down syndrome is accurate about 84% of the time. That means roughly 1 in 6 positive results turn out to be wrong.
What “Positive” Actually Means
Prenatal tests fall into two categories: screening tests and diagnostic tests. These are fundamentally different. A screening test estimates risk. A diagnostic test gives a clear yes or no. When people talk about a “positive Down syndrome test,” they’re almost always referring to a screening result, not a diagnosis.
The most common screening tests include the first-trimester screen (a combination of blood work and ultrasound, done between weeks 11 and 13) and cell-free DNA screening, which analyzes fragments of fetal DNA circulating in your blood. Both can flag an increased chance of Down syndrome, but neither can confirm it. The false positive rate for cell-free DNA screening is low, around 0.13%, but because the test is given to so many people, false positives still happen regularly.
The positive predictive value, the likelihood that a positive result is truly correct, depends heavily on your age and baseline risk. Across a large study population, cell-free DNA screening had a positive predictive value of 84% for Down syndrome specifically. For other conditions these screens check for, accuracy drops significantly: 76% for trisomy 18, 45% for trisomy 13, and as low as 26% for Turner syndrome. This is why professional guidelines are clear that no screening result alone should be treated as a diagnosis.
What Happens Next
The American College of Obstetricians and Gynecologists recommends three things after a positive cell-free DNA result: genetic counseling, a detailed ultrasound, and the option of diagnostic testing. You are not automatically funneled into any procedure. Each step is a choice.
A genetic counselor will walk you through what your specific result means given your age, family history, and the type of screening you had. Their role is to help you understand the numbers and decide what you want to do next, not to push you in any direction. During the consultation, you’ll review your family health history, discuss the accuracy of your particular screening result, and talk through the options available to you.
A detailed anatomic ultrasound can sometimes reveal physical markers associated with Down syndrome, like heart defects or differences in bone length. On its own, an ultrasound can’t confirm or rule out the condition, but it adds useful information to the picture.
Diagnostic Testing Options
If you want a definitive answer, two diagnostic tests can provide one. Both involve collecting a small sample of fetal cells and analyzing the chromosomes directly.
Chorionic villus sampling (CVS) can be done between weeks 10 and 13 of pregnancy. A small tissue sample is taken from the placenta. The risk of miscarriage from CVS is less than 1%, according to Cleveland Clinic data.
Amniocentesis is typically performed between weeks 14 and 20. A thin needle guided by ultrasound withdraws a small amount of amniotic fluid. When performed by an experienced provider, the miscarriage risk is lower than CVS, roughly 0.1% to 0.3%. Research suggests that amniocentesis done before 15 weeks carries a somewhat higher risk of pregnancy loss than when done later in that window.
Both tests are highly accurate for chromosomal conditions like Down syndrome. The choice between them often comes down to timing. If you’re early in pregnancy and want answers sooner, CVS is available weeks before amniocentesis. If you’re already past 13 weeks, amniocentesis is the standard option.
You can also choose not to pursue diagnostic testing at all. Some parents decide that the screening result, combined with ultrasound findings, gives them enough information. Others prefer certainty. Neither choice is wrong.
If the Diagnosis Is Confirmed
A confirmed diagnosis of Down syndrome opens a different set of decisions, and there’s no single “right” path. Some parents use the information to prepare for their child’s arrival. Others weigh whether to continue the pregnancy. Both are deeply personal choices, and genetic counselors are trained to support you without judgment regardless of what you decide.
For parents who continue the pregnancy, early preparation can make a real difference. Down syndrome affects children in a wide range of ways. Some children have significant heart defects that need surgical attention shortly after birth, while others have relatively mild health challenges. Knowing the diagnosis in advance lets your medical team plan for any complications at delivery and connect you with specialists early.
Early intervention programs, which include speech therapy, physical therapy, and developmental support, are available in every state and can begin shortly after birth. Organizations like the National Down Syndrome Congress offer resources specifically designed for new and expectant parents, including peer support from other families. The National Down Syndrome Society publishes guides on everything from early childhood development to educational planning. Family Voices, a national network, helps parents navigate healthcare systems for children with disabilities.
The Emotional Weight of Waiting
The period between a positive screening result and a diagnostic answer is often the hardest part. It can take one to three weeks to get diagnostic test results back, and that uncertainty is genuinely difficult. Many parents describe feeling panicked after a positive screen, only to learn later that the result was a false positive.
It helps to remember what the numbers actually say. If your cell-free DNA screen came back positive for Down syndrome, there is still roughly a 16% chance the result is incorrect. That’s not a small number. Until a diagnostic test confirms the finding, you are dealing with a probability, not a certainty. Genetic counselors can help you interpret your individual risk more precisely based on factors specific to your pregnancy, and talking through the numbers with someone trained to explain them often makes the waiting period more manageable.