Fashion loves to break its own rules, then unbreak them, then pretend the rules didn’t exist, then act as though everyone knew the rules all along, and since from the outside there is only one rule – be thin – this leads to some quite complex conversations. One year, you will find a plus-size model on every catwalk, and the next year they will have vanished.

But the final frontier is the pregnant woman, or – pretty much interchangeably, because you always look pregnant for ages after you are, unless you’re Madonna – the breastfeeding woman. There was that brief moment in 1991, when Annie Leibovitz put a gravid Demi Moore on the cover of Vanity Fair wearing nothing at all (commentators describe her pose as the “hand-bra”). Nothing came after. The pregnant woman remained culturally invisible, which really is a curious sensation when you’re in it, given how ginormous you are.

New York fashion week broke that article of faith last year, when the Eckhaus Latta show featured Maia Ruth Lee, who was eight months pregnant at the time, wearing a cardigan dress with a perfectly domed opening for her mighty tum, like something a midwife might design if he or she were in such a rush they wanted to measure everyone’s fundus by eye. But that reminded everyone: there actually had been some pregnant catwalk models, this decade. You could fit them all into two taxis, like the Lib Dems, but nine is more than none.

There was Jourdan Dunn for Jean Paul Gaultier’s spring/summer 2010 show and Italian model Bianca Balti for Dolce & Gabbana’s autumn/winter 2015 collection.

New Zealand model Ashleigh Good was the final showstopper in the Chanel show for autumn/winter 14/15, looking so pure and punk, so breathtakingly wonderful, that close observers may have felt that chill of the truly unattainable standards of fashion: to meet its trend criteria, you might have to get pregnant.

Victoria’s Secret has been at the vanguard, accounting for three of those nine. But its catwalk always has an uncomfortable relationship with the fashion mainstream, being too raunchy and saucy and seeming to miss the point (it’s art, not clothes-porn), but every now and then sailing past the point to make a new and possibly better one.

Jenni Kayne, an LA brand you might put into the category athleisure, saw sales triple after an image of TyLynn Nguyen breastfeeding went up on billboards in New York this month, defying marketing truisms (who last bought something they saw on a billboard? Nancy Reagan?) but also deeper assumptions about where our ego sits in relation to images of female beauty. If we were simply spectators to the more urgent male gaze, a breastfeeding woman would be like a regular woman, only not as good. But if we’re projecting ourselves, our hopes and memories, on to the image, then it makes perfect sense for this to spike sales, since breastfeeding is a much more profound romantic experience than, say, having a shower.

It would be fanciful to claim that pregnant models do much to spread the idea that pregnancy is, in itself, beautiful. But I still find the development quite heartening, for putting the female audience at the centre of an art form. For a bloody change.