What Is the Nub Theory Gender Test & Does it Really Work?

When my friend, Ashley, first told me she was pregnant with a girl — at only 11 weeks — I couldn’t hide my curiosity. Finding out a baby’s gender doesn’t usually happen until the 20-week ultrasound (unless you do special genetic testing). So, how could she possibly know her baby’s gender so much earlier than that? Ashley explained that she’d opted for a slightly less conventional gender prediction technique by trying to determine her baby’s sex with a method called the Nub Theory Gender Test.

What is the Nub Theory Gender Test?

The nub itself is a genital tubercle that appears in the first trimester and will develop into either a penis or a clitoris. Interestingly, in the those early weeks the nub kind of looks like a penis either way, so the only way to determine a baby’s gender (by the nub) is to analyze the angle of the dangle.

How do you do it?

  • Grab your first ultrasound picture (a pretty clear profile shot helps).
  • Draw a line along the base of your baby’s spine (the baseline).
  • Now comes the hard part: identifying the nub. Look for a small lump near the fetus’s butt (it kind of looks like a tail).
  • Draw a line of the nub in relation to the baseline (it should create a pie-shaped angle rather than parallel lines).

What do the results of the Nub Theory Gender Test?

If the nub appears to be tilting upward at an angle that’s greater than 30 percent (big pie-wedge), it means you are having a boy. If the nub is fairly level or even slanting down a bit, that suggests you are having a girl.

Does it really work?

Not really. According to Eden Fromberg, DO, of Holistic Gynecology New York, in New York City, environmental and industrial toxins (like BPA which is found in everything from plastic water bottles to cash register receipts and recycled toilet paper) can alter the nub. “BPA is associated with changes in genital development of the penis and testicles,” she explains. Endocrine disrupting chemicals will not deform all male (or female) genitalia — don’t worry! — but the fact that it could influence development makes the idea of nub gender testing less reliable. In Dr. Fromberg’s opinion, the nub theory gender test should only be used by a medical professional who is testing for chromosomal abnormalities. “Otherwise (nub theory) is for entertainment value only,” she says. “It’s better to wait a month or two until after your anatomy scan, when your baby’s gender can be more reliably identified, to purchase gender specific baby items.”

More for Pregnant Moms:

30 Totally Cool Gender Reveal Ideas
7 Pregnancy Old Wives Tales That Were True for Me
31 Creative Ways to Tell Your Husband You’re Pregnant