New craze sees mums-to-be asking strangers online to guess their baby’s sex

Mums-to-be are asking strangers to guess their baby’s sex by posting scan pictures online, in a wacky new craze sweeping the internet.

Traditional medical scans won’t determine whether a baby is male or female until 20 weeks.

But some experts think it is possible to predict the foetus’ sex at 12 weeks, by analysing the skull shape and ‘nub’ area between the legs.

Boys predominately have squarer chins, a chunkier skull shape and more pronounced brow ridge, whereas girl’s skulls have a smaller brow ridge and more pointed chins.

Babies with a ‘nub’ – or genital tubercle – angled at greater than 30 degrees are likely to be boys, while girls’ nubs sits below 30 degrees.

Some experts claim up to 88 per cent accuracy using the technique – making it more effective than the 75 per cent of parents who said their 20-week scan correctly predicted their baby’s sex.

The fast-growing worldwide trend has seen an explosion in dedicated online ‘nub and skull’ forums where medics guess the infant’s sex.

According to a study by parenting site ChannelMum.com 45 per cent of pregnant women now take part in the phenomenon known as the ‘nub and skull theory’.

ChannelMum.com gender expert Lisa Lum said: “The Nub and Skull theory is the fastest-growing gender prediction technique simply because it’s so social.

”Three quarters of mums who try it say they like getting other people’s opinions on their child’s sex while 30 per cent see it as a worldwide craze they like to be part of.

”While no non-medical technique is 100 per cent accurate, it’s fun and brings people together, which is exactly what children should do at all ages.”

The study also found one in five (21 per cent) mums-to-be have posted their picture for an expert to predict the sex, compared to just seven per cent who show the image to their midwife.

And one in ten mums said studying the scan picture with strangers helps them bond with their baby.

Another 63 per cent said they ask midwives at the 20-weeks scan.

While almost half of parents (45 per cent) try the nub method, 27 per cent also looked at the shape of their baby’s skull.

The theory claims boys have square chins, a chunkier skull shape and more pronounced brow ridge whereas girl’s skulls have a smaller brow ridge and more pointed chins.

Overall, the study of 1,275 parents found three quarters (72 per cent) of mums and dads want to find out their unborn baby’s sex.

The most popular method remains asking the 20-week scan with 63 per cent of mums quizzing medical staff on their child’s sex.

Also fashionable is the ‘Chinese Gender Prediction’ calendar which guesses the sex based on the date couples conceive and is tried by over half of mums (57 per cent).

A further 48 per cent try to work out of they are having a girl or a boy by the size and shape of their bump and 45 per cent use the ‘heart rate theory’ which claims a foetus’ heartbeat above 140 beats per minute is more likely to be a girl.

Meanwhile 44 per cent analysed their food cravings and 30 per cent tried an old wives tale of dangling a ring on a piece of string above the bump, with a circling ring indicating a girl and side-to-side movement meaning a boy.

One in five even tried to guess their tot’s sex from the amount of morning sickness they suffered, with worse sickness believed to show a baby girl.