How to Read NIPT Results for Gender Labcorp

Labcorp NIPT results report fetal sex as “Male” or “Female” based on Y‑chromosome DNA; accuracy is high after 10 weeks, but NIPT is a screening test.

You waited about a week, checked your Labcorp patient portal, and finally saw the words: “Fetal Sex: Male” or “Fetal Sex: Female.” It feels like the big reveal—but that single line sits inside a larger report full of chromosome numbers, risk scores, and medical jargon. Most of it matters for different reasons.

Knowing how to read NIPT results for gender from Labcorp means understanding what that sex call is based on, why it’s rarely wrong but not perfect, and what to do if the result says “no result” instead of a gender. Here’s what to look for and what the rest of the report is telling you.

Where the Gender Result Appears on a Labcorp Report

Labcorp’s MaterniT NIPT sample report includes a result summary near the top. The fetal sex line is usually labeled clearly—”Fetal Sex” followed by “Male” or “Female.” It appears separately from the trisomy screening results (T21, T18, T13).

Below that summary, there’s a table that shows whether an increased amount of chromosome material was detected. The fetal sex line doesn’t use a “positive” or “negative” flag; it’s a simple binary call based on Y‑chromosome presence. If Y‑chromosome DNA fragments are found in your blood sample, the result is Male. If not, it’s Female.

The test looks for cell‑free fetal DNA circulating in your bloodstream. That’s the same DNA used to screen for common chromosomal conditions—sex determination is an additive feature, not the test’s primary purpose.

Why the Gender Call Is Usually Trustworthy (But Not a Guarantee)

When you’re reading NIPT results for gender, a healthy dose of confidence is fair—but a tiny sliver of uncertainty matters. NIPT is often described as about 99 percent accurate for sex determination when performed at or after 10 weeks, according to some pregnancy resources. That leaves roughly a 1 percent chance that the call could be off.

Why would it be wrong? A few biological factors can interfere:

• Low fetal fraction: If blood is drawn too early (before 9–10 weeks) or if your fetal DNA percentage is low, there may not be enough Y‑chromosome material to detect a male fetus, producing a “female” result by mistake.
• Vanishing twin: If a twin pregnancy ended early, residual Y‑chromosome DNA from the vanished twin can linger in your blood, causing a false male result for a female singleton.
• Confined placental mosaicism: The placenta’s DNA doesn’t always match the baby’s exact chromosome makeup. This is a known source of false‑positive and false‑negative NIPT calls.
• Rare maternal conditions: A prior male pregnancy can leave tiny amounts of male DNA in the mother’s bloodstream, or maternal mosaicism (where some of the mother’s own cells have a Y chromosome) can confuse the test.
• Laboratory or technical errors: Sample mix‑ups, insufficient blood volume, or processing issues can produce a wrong reading, though these are uncommon.

The bottom line for gender: a “Male” result is correct the vast majority of the time, but if anything about your pregnancy history (such as a vanishing twin) could skew the test, let your provider know before you buy the blue ones.

Reading Beyond the Gender Line: Chromosome Risk Results

The rest of the Labcorp report is more important clinically than the sex line. For each chromosome screened (21, 18, 13, and sometimes the sex chromosomes), the result will say “An increased amount of chromosome 21 material was detected” or “No increased amount of chromosome 21, 18, or 13 material was detected.” Negative results are reassuring—but a peer‑reviewed review in NIPT requires diagnostic confirmation because false negatives are possible, though rates are low.

A “positive” or “anomaly detected” result for a chromosome condition should never be taken as a diagnosis. It means the test found more fetal DNA from that chromosome than expected. The next step is diagnostic testing—chorionic villus sampling (CVS) or amniocentesis—to confirm or rule out the finding.

Your report may also include a fetal fraction percentage. A fetal fraction below 4% is considered low and increases the chance of a no‑result or inaccurate result. If that happens, your provider may recommend a repeat draw after a week or two, or skip NIPT and move directly to ultrasound or diagnostic testing.

One important note: a negative NIPT result does not ensure an unaffected pregnancy. Labcorp’s own sample report states that there is still a residual risk of chromosomal abnormalities. No screening test is perfect.

How to Access and Share Your Labcorp NIPT Results

Labcorp puts your results in your online patient portal as soon as they’re ready. Log into your account and look for the test name, usually “MaterniT21 PLUS” or “MaterniT GENOME.” Results typically post within a few days of the lab receiving your blood sample.

1. Check the “Fetal Sex” line first for the gender call. It is clearly labeled. Don’t confuse it with the chromosome risk results below.
2. Look at the chromosome results table to see whether any “increased material” flags appear. If everything says “no increased material,” that’s a negative screen.
3. Note the fetal fraction if it is included. Some reports list it; if it’s below 4%, discuss the accuracy of the results with your provider.
4. Contact your OB or midwife for interpretation—they have your full medical history and can explain what the results mean for your specific pregnancy.
5. Save a PDF or screenshot for your records and for any specialist visits.

If you’re sharing the report with a partner or family member, point out the gender line but also explain that a low‑risk result is not a guarantee of a healthy baby. The report is a screening tool, not a final verdict.

What to Do If Your NIPT Result for Gender Is Incomplete

Sometimes the Labcorp report says “No result” or “Incomplete” for fetal sex. This happens most often when the fetal fraction is too low—your blood didn’t contain enough fetal DNA for the test to make a call. It is more common in early draws, certain maternal weights, or with multiple gestations.

Clinical guidance from genetics laboratories suggests that repeating the NIPT is not the best approach if the result is incomplete. Instead, an incomplete NIPT result next steps typically involve moving to fetal ultrasound (around 18–20 weeks) or diagnostic testing if chromosome screening is still needed. Your provider may also recommend a repeat blood draw if the timing was borderline.

An incomplete result does not mean something is wrong with the baby. It means the test couldn’t process enough fetal DNA. Many women go on to have a normal pregnancy and learn the sex at the anatomy scan. The key point: don’t order another NIPT without talking to your doctor first.

The Bottom Line

Reading NIPT results for gender from Labcorp is straightforward once you know where to look: the fetal sex line near the top of the report. But the real value of the test lies in the chromosome screening results, which require follow‑up if flagged. Gender accuracy is high after 10 weeks—some sources put it around 99 percent—but it’s still a screening call, not a guarantee.

If your result is incomplete or you have questions about what “Male” or “Female” means given your pregnancy history, your obstetrician or midwife can review the fetal fraction, timing, and any confounding factors like a vanishing twin to give you a confident answer tailored to your situation.