QNatal Advanced results are reported using straightforward terms: “negative,” “positive,” or “increased risk,” depending on what’s being screened. But understanding what those terms actually mean for your pregnancy, and what the additional numbers on your report tell you, takes a bit more context. Here’s how to read each part of your results.
What the QNatal Test Screens For
QNatal Advanced is a cell-free DNA screening test offered by Quest Diagnostics. It analyzes tiny fragments of placental DNA circulating in your blood to check for chromosomal conditions in your baby. The test screens for three major trisomies (where there’s an extra copy of a chromosome): trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome), and trisomy 13 (Patau syndrome). It also screens for sex chromosome differences like Turner syndrome, Klinefelter syndrome, Triple X, and XYY syndrome.
Beyond those, QNatal includes an optional microdeletion panel that looks for small missing pieces of chromosomes linked to conditions such as DiGeorge syndrome (22q11.2 deletion), Prader-Willi and Angelman syndromes (15q), Cri-du-chat syndrome (5p), and several others including deletions at 1p36, 4p, 8q, and 11q. If your provider didn’t opt out of microdeletion screening, those results will appear on your report too. Fetal sex is also reported unless you’ve asked not to know.
Negative Results
A “negative” result for trisomy 21, 18, or 13 means the test did not detect extra copies of those chromosomes. This is the result most people receive, and no specific follow-up is needed. It’s worth remembering that “negative” means low risk, not zero risk. Cell-free DNA screening is highly accurate but is not a diagnostic test. The detection rate is roughly 93% for trisomy 21, 89% for trisomy 18, and lower for trisomy 13, which means a small number of affected pregnancies will still get a negative result.
Positive Results and the PPV Number
For the three major trisomies, a “positive” result means the test detected a pattern consistent with an extra chromosome. Every positive result on your report will include an important number called the positive predictive value, or PPV. This is the piece most people need help interpreting.
The PPV tells you the probability that a positive result is a true positive, adjusted for your age. A PPV of 90% means that out of 100 people with the same result and age profile, about 90 would have a confirmed chromosomal condition and 10 would not. In large studies of this test’s platform, the PPV was about 98% for trisomy 21, 88% for trisomy 18, and 59% for trisomy 13. That last number is key: a positive result for trisomy 13 is actually a false alarm roughly 4 out of 10 times. Your individual PPV may differ from these averages because it factors in your specific age-related risk.
A positive result is not a diagnosis. The recommended next step is genetic counseling followed by a diagnostic procedure, either chorionic villus sampling (CVS) or amniocentesis, which directly examines fetal chromosomes and gives a definitive answer.
Increased Risk Results
Sex chromosome conditions and microdeletions use different language on the report. Instead of “positive,” these are labeled “increased risk.” The distinction exists because these findings are less predictable than trisomy results. In clinical studies, the PPV for sex chromosome conditions was around 69%, and for microdeletions it was about 75%, meaning false positives are more common in these categories. If your report shows “increased risk” for any of these, genetic counseling and possibly diagnostic testing are the typical next steps.
Non-Reportable or Inconclusive Results
Sometimes the lab can’t generate a result at all. Your report may say “non-reportable” or “inconclusive,” and this simply means the test couldn’t be interpreted. The most common reason is that there wasn’t enough fetal DNA in your blood sample. The test requires fetal DNA to make up at least 3.5% to 4.5% of the total cell-free DNA present. If the proportion falls below that threshold, the lab can’t reliably distinguish fetal chromosome patterns from maternal ones.
Several factors can lower the amount of fetal DNA in your blood. Higher body weight is the most common: for roughly every 11 pounds of additional maternal weight, the fetal DNA concentration drops measurably due to a dilution effect from increased blood volume. Early gestational age also plays a role, since fetal DNA levels rise as pregnancy progresses. In one study, women who got results on a second attempt were on average about two and a half weeks further along than they were at the first draw. Less commonly, certain autoimmune conditions, blood disorders, or blood-thinning medications can interfere with the test.
If you get a non-reportable result, your provider will typically recommend a repeat blood draw. If the second attempt also fails, diagnostic testing with amniocentesis or CVS is appropriate. A failed result isn’t itself a positive, but it is associated with a slightly higher chance of chromosomal abnormalities compared to the general population, so it shouldn’t be dismissed as “probably fine.”
Fetal Fraction on Your Report
Some QNatal reports include the fetal fraction percentage. This number tells you what proportion of the cell-free DNA in your blood sample came from the placenta (and therefore represents the baby). A higher fetal fraction generally means the result is more reliable. Most successful tests have a fetal fraction well above the 3.5% to 4.5% minimum. If your fetal fraction is listed and it’s on the lower end, the result is still valid if it was reported, but it provides context for how much DNA the lab had to work with.
Fetal Sex
If you opted to learn the baby’s sex, the report will indicate either XX (female) or XY (male) based on the presence or absence of Y-chromosome DNA. This determination is highly accurate when fetal fraction is sufficient. Very early in pregnancy or at very low fetal fractions, there’s a small chance of an incorrect sex call, particularly for male fetuses where trace Y-chromosome DNA might be missed.
How to Access Your Results
QNatal results are typically available within 5 to 14 days of your blood draw. You can view them through MyQuest, the free patient portal at MyQuestResults.com, or through your provider’s office. Complex prenatal screens like QNatal tend to fall on the longer end of the turnaround window. If your provider reviews results with you in a scheduled appointment rather than releasing them directly, the timing will depend on your office’s scheduling.
What to Do With a Positive or Increased Risk Result
The single most important thing to understand about any positive or increased risk result is that this test is a screening tool, not a definitive answer. The American College of Obstetricians and Gynecologists recommends that any positive cell-free DNA result be followed by genetic counseling and an offer of diagnostic testing. Diagnostic procedures like amniocentesis (performed around 15 to 20 weeks) or CVS (performed around 10 to 13 weeks) analyze actual fetal cells and provide a confirmed yes or no.
A comprehensive ultrasound is also typically part of the follow-up, both to look for physical markers associated with chromosomal conditions and to evaluate fetal anatomy. In cases where a structural abnormality is seen on ultrasound, diagnostic testing becomes especially important regardless of what the screening result says.