It’s a guessing game that has amused people for generations. Whether you want to find out before the baby is born or not, myths and old wives tales such as cravings, the way you are carrying and the ring test have been fun ways to try to predict the sex of your baby, without any scientific fact whatsoever.

Recent studies have suggested that fetal sex can be identified at the 12 week scan by assessing the angle of the genital tubercle. Most sonographers feel it is too early to determine the fetal sex by ultrasound at the 12 weeks, offered routinely on the NHS either as a dating scan or First Trimester Combined Screening.

The popular ‘Nub theory” has little foundation.  A male and female baby’s sexual organs will look very similar, so assessing the angle at which it is lying is very difficult until they are sufficiently developed.

It is only after the 16th week of pregnancy when the baby’s sexual organs have grown to a point at which they can be correctly identified.

Up until this point, these look very similar and the results inconclusive, and that is the reason why it is vitally important to do this at the right time to avoid any inaccurate outcomes. At the correct gestation, a boy’s testicles and penis can be seen clearly on an ultrasound scan, as can a girl’s labia.

What does have an influence on whether the fetal sex can be identified is the co-operation of the baby. It is impossible to see the genitalia which obviously determine if the fetus is a boy or a girl if the legs are crossed, or the bottom down in the mother’s pelvis. If this happens, it is a case of trying to encourage the baby to move. We initially ask mums to come with a full bladder, and to go for a brisk walk and come back to see if the activity helps the baby into a new position, play music, or encourage Mum to eat something sweet.

If you do decide you want to find out whether you are carrying a boy or a girl, and before you have the ‘gender reveal’ scan at around five months, indulge yourself by playing guessing games and old wives tales– just don’t start painting the nursery.


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