The new craze is sweeping the nation, led by proud new mums who believe that anyone other than themselves and the fathers care about the sex of their baby.
Whatever next? The Pregnancy Test Kit Reveal Party, perhaps?
In the States, websites have been set up offering 'revealing' mums the chance to buy decorations, party food and baby clothes – all with a colour theme to denote the sex of the pending arrival.
Over here, women can get a cake baked that, beneath neutral icing, hides pink or blue sponge. In some cases, expectant mums ask the sonographer at their 20-week scan to keep their baby's identity secret and to put it in a sealed envelope.
Mum-to-be then pops along to her local cake maker and asks them to bake a cake with the envelope sealed inside. More novel than choc chips and raisins, but not nearly as tasty!
Pioneering the American import over here is Lisa Finnigan, who runs Pretty Princess Cakes and Cupcakes in Cheshire.
Hers is now one of a growing number of UK cake shops catering for the trend, with the special cakes pictured among the wedding and birthday confectionery on her website.
"People are just slowly catching on around here," she said.
"I haven't had anyone who has done the sealed envelope from the doctor yet, but nothing surprises me any more about what people ask for. It's been fun to do it, though.
"One couple did it because they both had children from previous relationships and they wanted those children to be involved in the new baby, so they did it for them.
"Having a big family party and the cake was really nice. I do get why they did it."
One of Lisa's first clients was her friend Michelle Whitney, 27, who threw a Gender Reveal Party to surprise 40 friends and family about the sex of her baby daughter, Betsy.
"My cousin, who has been my bridesmaid, was leaving for New Zealand and I really wanted her to know what I was having before she went," Michelle said.
"I hate baby showers because I didn't want people giving presents to a baby before it's born; it's unlucky and tacky.
"Then I saw all these videos on YouTube of women cutting open gender-revealing cakes in America and I thought it was a great idea."
And although Betsy's gender was news to her family, Michelle knew her daughter's sex.
"There was no way I wasn't going to be the very first to know," she said.
Michelle, who already had a baby boy, cut into the icing to reveal the the first slice of pink sponge. "It was a fantastic occasion," she told BBC Breakfast.
Baker Lisa said that the cakes available in the U.S. might be a bit too over-the-top for British tastes. One that has icing reading "Am I a superhero in blue or a Pretty Princess in pink?" is popular, while guests are often asked to come dressed for their preferred result – "team blue" for a boy or "team pink" for a girl. And unlike baby showers, dads, uncles and male friends are invited too.
But for all the enthusiasm for the idea – on blogs, YouTube, Facebook and Twitter - there are cynics. "When will smug mothers-to-be realise that no one but them really cares too much," said one parent.
What do you think? More excuses to sell you stuff before the baby's even born or a fun idea?
More on Parentdish: The other extreme - the UK couple who kept their child's gender secret for five years!