It's called Doing A Demi – a phrase that has crept into the vernacular to describe any heavily-pregnant woman (usually famous) who sheds her inhibitions to display her bare bump.
And the latest star to go nude is Sienna Miller - showing a whole lot more than any of her predecessors.
The craze was started in August 1991 when Demi Moore posed on the cover of Vanity Fair while seven months pregnant with her second child, Scout.
She was followed by Cindy Crawford, Claudia Schiffer, Myleene Klass, Jessica Simpson, Danielle Lloyd and others – all completely naked, but still covering their modesty with strategically placed hands and arms.
Artist Jonathan Yeo painted Sienna shortly before the arrival of her first baby, Marlowe, as part of a series of portraits, including Nicole Kidman and model Erin O'Connor, to be exhibited next year.
Yeo, 41, said it was a 'tribute to her courage and self-confidence' that the actress, 30, agreed to sit for him in July only weeks before the arrival of her daughter by On The Road star Tom Sturridge.
"I can think of many figures whose public currency in part revolves around their appearance, who would prefer to hide themselves away for nine months," the artist said.
"Sienna is usually so petite and such a wonderful fashion clothes horse, and the fact she is so transformed means it has all the more impact.
"There is a nervousness but I think it's the anticipation of becoming a parent - that thing that your life is about to change."
He said that Sienna was a 'fabulous' subject, adding. "She is bright, she is so chatty, she makes me laugh endlessly. And because she's an actress, she is a chameleon and can look very different in different ways. Her job is to be looked at but I guess the way I look at her is a bit different from the way movie cameras or fashion cameras do."
What do you think? A beautiful portrait or 'put it away'?
More on Parentdish: Why pregnant women should be proud of their bodies
• Some People, November 16 to December 8, at Eleven, Eccleston St SW1. www.jonathanyeo.com