healthHealth and Medicine

Finger-Prick Blood Test Reveals Your Baby's Sex Way Earlier Than An Ultrasound Scan


Robin Andrews

Science & Policy Writer


Click. Boom. Done. Aomboom/Shutterstock

If you’re not an expecting mother that likes to wait until the end of the exhausting pregnancy journey to find out whether you’ve spawned a boy or a girl, then you’ve likely gone for your second routine ultrasound checkup around 18 to 21 weeks post-conception.

It may soon be time to forget that gooey tummy gel and a blurry image of a baby hiding in the womb, however. A new study, published in the journal Prenatal Diagnosis, describes a quick, finger-prick blood test that can determine the sex of your still-cooking offspring within the first trimester (until the 12th week).


Tests like this already exist, mind you. Such blood-based examinations – currently privately available in the UK – are used to detect Down syndrome, along with several others, including Edwards’ and Patau’s syndromes. Termed the non-invasive prenatal test (NIPT), it’s meant to make an early diagnosis of such syndromes safer.

Ordinarily, in order to test for these syndromes, amniocentesis is opted for. This involves extracting a sample of cells from the amniotic fluid, which surrounds and protects the developing baby in the womb. This, unfortunately, brings with it a small risk of a miscarriage occurring, something that NIPT avoids.

NIPT, whether it’s looking for evidence of such conditions or is being used to determine the sex of the almost-child, works by taking a blood sample from the expecting mother using a syringe. This is as non-invasive as the test has managed to be at this point.

Now, however, as first spotted by New Scientist, this new study makes everything a little simpler and more streamlined. Instead of any nasty massive needles, all you need is a single drop of blood from your finger to find out what kind of hellraiser you’ll be having.


Led by Sabin Laboratory, a Brazilian medical diagnostics company, it involved recruiting 101 pregnant women, each who gave away a solitary blob of their crimson to be analyzed via said finger-prick method. The team then had a poke around for the male-exclusive Y chromosome with fragments of fetal DNA, which allowed them to find out whether a boy or girl was on the way.

The test results – corroborated with later clinical examinations of the newborn at birth – was deemed reliable if carried out after the 8th week of gestation. It’s reported to be able to, overall, correctly determine the presence of the Y chromosome 95.4 percent of the time; this is around the same accuracy as an ultrasound test, but far earlier and with far less hassle.

The only potential problem is that these blood samples are more vulnerable to be contaminated by foreign DNA on the surface of the finger, which can lead to some false positives. Venous blood doesn’t present this problem, but the team note that proper cleaning of the finger immediately preceding the test circumvents this issue.

It’s not clear whether the test can be used to look for those aforementioned syndromes or other malevolent genetic conditions, and at present, this is a proof-of-concept design. It’s not yet available for use, although it probably won’t be long until it will be.


As with such tests, there’ll likely be worries about this new method making sex-specific abortions easier – but that’s a debate for another time.


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  • detection,

  • blood test,

  • Y chromosome,

  • proof-of-concept,

  • first trimester,

  • 8th week,

  • finger-prick,

  • genetic disorders,

  • syndromes