Your pregnancy, your midwife, your choice


20 Oct

Nub Theory

What is nub theory?

Is it true about the angle of the dangle?

Can you really find out your babies sex at 12 weeks?

Any best guess would be only slightly better than 50/50 and would have to be confirmed again at the anomaly scan at around 20 weeks. The honest truth is that it is very difficult for a sonographer to see clearly all the structures at dating scan and the genitalia of a fetus at this stage is very unclear and looks very very similar for both male and female foetuses.

'The correct visualization of any fetal part depends on many factors such as fetal position, amount of amniotic fluid and thickness of the abdominal wall. Establishing gender can sometimes be very difficult.'

The theory is as follows:

The following images are from 12-14 weeks.

Image 1: Supposed male fetus in development. With the male fetus, the genital tubercle usually creates an angle of greater than 30° with the lower part of the spine.

Image 2: Supposed female fetus in early development. In the female fetuses, the genital tubercle protrudes in the same direction as the lower portion of the spine with an angle of less than 30° relative to the backbone.

Various studies have supposedly been done to test this theory.

Studies have been conducted in Brazil, London (2studies) and Israel. Out of a total of 1619 pregnancies; gender was assigned and confirmed in 1424.

The results when combined together found that genre was accurately predicted at:

11 weeks 68%
12 weeks 88%
13 weeks 94%
14 weeks 98%


I must highlight that I have searched one of the biggest online journal forums on the internet (which has never failed me when it comes to medical research) and I couldn't find any of these supposed studies!!

You must also remember ladies that not all sonographers will be trained to recognise and capture images like the ones here. This is not something we usually look at so early on.

I personally and professionally am not convinced. You may believe what ever you like though and I would LOVE to see the original articles and research if anyone has any links to them then please post them below.

Post by Sally Barnes, One to One Midwife

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