TikTok ultrasound tech's blood test claims, fact-checked

What did @natalieavni actually say?

The creator, who identifies as an ultrasound tech with six years of experience, explains that a non-invasive prenatal test (NIPT) screens for chromosomal abnormalities like Down syndrome and can also determine fetal sex. She recommends waiting until around 11 weeks to get the test, arguing that testing at 10 weeks or earlier can produce inconclusive results. She states she personally has never seen a wrong gender result from the test, though she acknowledges hearing about errors online. She also describes confirming fetal sex via ultrasound once she can visualize it.

The video is framed as a response to a follower question and draws primarily on personal clinical observation rather than published research. That framing matters when evaluating what she says.

Does the science back this up?

Mostly, yes, but with important caveats she glosses over. NIPT is highly accurate for fetal sex determination, but "highly accurate" is not the same as "never wrong."

A 2015 meta-analysis by Devaney et al. in Genetics in Medicine, covering over 3,000 pregnancies, found NIPT fetal sex determination had a sensitivity of 95.8% and specificity of 98.9% for male identification. A 2019 systematic review by Meng et al. in Ultrasound in Obstetrics and Gynecology confirmed accuracy rates above 98% when testing occurred after 10 weeks of gestation. The timing recommendation around 10 to 11 weeks is supported by data: fetal cell-free DNA (cfDNA) fractions are lower before 10 weeks, which increases the rate of inconclusive or failed results. The American College of Obstetricians and Gynecologists (ACOG) notes that a fetal fraction below 4% is the most common reason for a no-result report.

So her advice to wait until 11 weeks is reasonable. Her claim that results are essentially never wrong is where the science parts ways with her anecdote.

What did they get wrong (or right)?

She got the core biology right. NIPT is a chromosomal analysis, timing does affect result quality, and the test is genuinely useful for early sex determination alongside its primary purpose of screening for aneuploidies. Credit where it is due.

What she gets wrong, or at least overstates, is the error rate framing. Saying "I haven't seen anything come back wrong" is an anecdote from one clinic's patient population. It is not evidence that errors do not occur. False sex assignments do happen, most commonly in cases of vanishing twin syndrome, maternal sex chromosome mosaicism, or very low fetal fraction. A 2021 study by Hartwig et al. in Prenatal Diagnosis documented cases where NIPT incorrectly reported male sex in female fetuses due to maternal mosaic conditions. The creator briefly acknowledges internet reports of errors but dismisses them too quickly. Those reports often have biological explanations that do not reflect lab failure, but they are real and deserve more than a shrug.

Her conflation of "inconclusive" with "wrong" is also worth flagging. An inconclusive result is a quality control signal, not an error. They are different problems with different causes.

What should you actually know?

NIPT is one of the most accurate prenatal screening tools available, but it is a screening test, not a diagnostic test. That distinction matters. A positive NIPT result for a chromosomal abnormality should always be followed by confirmatory diagnostic testing like amniocentesis or chorionic villus sampling. For fetal sex, the accuracy is genuinely high after 10 weeks, but "high" still means a small percentage of results can be incorrect.

If you receive a sex result from NIPT that surprises you at the anatomy ultrasound around 18 to 20 weeks, do not panic. Ask your provider to review the original fetal fraction percentage and whether any flags appeared on the report. Low fetal fraction is the most common culprit for inaccurate sex calls.

• NIPT is offered starting at 10 weeks, with most labs recommending 10 weeks as the minimum and accuracy improving slightly through weeks 11 to 13.
• The test requires a maternal blood draw and analyzes cell-free fetal DNA circulating in maternal blood.
• Insurance coverage varies significantly. Not all plans cover NIPT for low-risk pregnancies.
• Fetal sex results from NIPT are not the same as a clinical diagnosis of a gender identity. The test identifies chromosomal sex, specifically XX or XY.