Between 12 and 14 weeks, if you can get the right view during your NT scan, you can make a pretty good guess of what the fetal sex is of your baby! What you need to get is a sagittal view of the baby, which is a vertical image of the body seen on its side like lying on a table, backside down(if the baby is inverted or upside down, then this approach will not work) and you need to be able to see the spine and the end of the baby where the nub is located.
Within this shot, at the end of the spine, there is a genital tubercle sometimes referred to as a genital ‘bump’ or nub. The gender determination is made by studying the angle between the genital bump(nub) and the direction of the lower portion of the spine.
If the angle that is created is greater than 30 degrees then it is a male and if the genital tubercle is parallel or less than a 10 degree angle to the spine, it is a female.
How accurate is a scan this early for determining gender?
Not 100% but pretty good. Out of 1,424 pregnancies in the study, at 11 weeks it was only correct 50% of the time but at 12 weeks, it showed to be 80% accurate and at 13 weeks, 94% accurate!
12 Week Baby Boy
12 Week Baby Girl