What is nub theory and does it work at 12 weeks?

IF you’re in the early weeks of pregnancy, it can seem like forever until your mid-pregnancy ultrasound where you'll find out the biological sex of your child.

That’s why there are plenty of different gender prediction methods, including the nub theory. Here's everything you need to know.

What is nub theory?

The nub theory is also known as the angle of the dangle.

It uses your baby's spinal cord and genital tissues forming at your first pregnancy scan to predict the gender of your baby.

The idea behind nub theory is that if you can get a really good look at this nub, you can figure out which way it will go in the coming weeks.

How can you predict gender from a 12 week ultrasound scan?

According to proponents of nub theory, you can work out your baby’s sex at a 12-week ultrasound.

While it's not recommended by midwives - the NHS recommends you wait until your second ultrasound between 18 and 21 weeks - many parents say they've used the nub test to make an educated guess earlier.

To apply the nub theory to your baby’s ultrasound, you need to catch them in a clear profile so the length of their spine is visible horizontally.

From there you would search for the nub, or a small protrusion, in between where your baby’s legs will form.

Mum Clementine Salmon told The Sun: ''The one thing I firmly believe in is the 'nub' test.

"As this is my third pregnancy I compared all three 12-week scans and all had the nub at the same angle.''

Becky Rutherford, a midwife sonographer, wrote for "The sex of your baby is fixed at conception. All embryos have a small bud or swelling (genital nub).

"If you're having a boy, testosterone starts being produced at seven weeks.

"Testosterone prompts the bud to grow and develop into a penis and scrotum. In a girl, the genital nub will become the clitoris and labia.

"Nub theory is based on the idea that it's possible to tell which type of genital nub your baby has from the dating scan image.

"But nub development is a gradual process, and it's a real challenge to see which way the nub is developing around the time of your dating scan."

The angle of the nub can supposedly tell you the sex of your baby.

If the nub is angled higher than 30 degrees in relation to its spine, that indicates your baby is a boy, according to nub theorists.

But if the nub is pointing straight out, under 30 degrees, or down, it is likely a girl.

Can you predict whether you are having a boy or girl at a 12 week scan?

The nub theory might seem like a fool-proof way to tell the sex of your little one, but midwives and other doctors recommend you wait until your second ultrasound, typically at 20 weeks, to be certain.

That's because it's incredibly difficult to determine the sex of your baby in the first trimester as the genitals haven't formed properly yet.

The main reason your second scan is done between 18 and 21 weeks is to check for physical abnormalities in your baby, but you can also ask the sonographer to check if it's a boy or girl.

Research conducted in 2012 indicates that even when ultrasounds are read by professionals, nub theory is only accurate about 30% of the time on fetuses less than 11 weeks’ gestation

If your baby is lying in an awkward position or moving around a lot, it may be difficult or impossible to tell whether your baby is a boy or girl, for example.

Some hospitals even have a policy to never tell expecting parents what the sex of their baby is - as there is still room for error even later in the pregnancy.

If your hospital has that policy you can always pay for a private scan to find out, but remember that it may still be wrong.

Let's face it though a healthy baby no matter what their sex is all any parent can hope for.