Style: Big news from the front

The whole process can be somewhat unsettling. After the excitement and congratulations, you survey your wardrobe and realise that what was once an old friend is now forbidden territory. It's not as if you can try to squeeze into your trouser suit and look vaguely fat. Think more along the lines of having a hard large ball stapled to your stomach, while the rest of your body stays reasonably the same shape. You have nothing to wear. At the same time you don't really feel like waddling around in a kaftan looking like Demis Roussos. And thus when the zip on my snappy little boucle suit from Oasis gave up the ghost, I realised I would have to start shopping specifically for my expanded frame.

"It's a pity you're not a policewoman," said my friend Paul. Apparently the minute their Predictor test goes blue, policewomen can dump their uniforms and slob around out of the public eye on Planet Legging for the next nine months. "Security reasons," said Paul.

However, most working women have to stay on show. So, it was off to inspect the ranges I was confident would exist in my favourite shops.

"Hello, Harvey Nichols? Do you have a maternity department?" The assistant reacts as if I have just walked in with E coli. "Oh no, no maternity here."

"But I thought you did all sorts of fashion?" I suggest. Call me Paula Yates, but this is a natural condition even for fashion victims. "Well, our designers don't do maternity. There's no call for it."

The woman at Selfridges thought there probably wasn't a call for it, either. "Ooh, no, we closed ours about a year ago. I don't think it was selling very well."

I don't even bother going into Oasis. I begin to envisage a life dressed entirely in clothes advertised by the National Childbirth Trust. Smocks, bras with zips, that sort of thing.

What about trail-blazing mothers-to-be like Carol Vorderman, maths whizz on Channel 4's Countdown? I bet she didn't go around in NCT gear, I think crossly.

"I think Emma Forbes got all her stuff from Dorothy Perkins," says my sister. Indeed, on investigation, Dorothy Perkins has been rather clever. With its competitors either turning a blind eye or having a wholly dismissive approach (witness Hennes, whose tiny range of dingy clothes in its "flagship" Oxford Circus branch is a) miles away from any changing-room and b) the size of a broom cupboard), DP appears to have cornered the high-street market. Nearly all its 550 stores carry a maternity range, which includes groovy suedette trousers, swing dresses and brightly coloured suits, with prices (pounds 10 to pounds 55 per item), which reflect the fact that you will probably only wear them for a few months.

Which, of course, is the reason most shops don't bother stocking the stuff at all. "Maternity lines don't make much money because most people don't want to spend any money on pregnancy gear," says Gill Lee, head maternity buyer at Harrods, which, almost alone among the department stores, has a section resplendent in expandable trousers and A-line dresses.

"Most women think they can get away with wearing their husband's shirts, but there comes a time when they realise they simply have to have properly designed stuff. Of course by then they are about seven months gone, and then it really is a waste."

Ms Lee, an extremely chic-looking woman (with a small son), is firmly in the "Proud to be Pregnant" camp. "We sell Lycra tube dresses here, very tight over the bump, and women look great in them. The idea is not to wear voluminous stuff which is two sizes too big and hides everything, but to buy stuff in your pre-pregnancy size and show your figure off with a well-cut suit. We have lots of professional women in here, older women maybe, who need to look smart for work."

To get you really into the antenatal swing, Harrods has maternity fitting- rooms equipped with a delightful range of "tummy cushions", to demonstrate how the clothes will hang.

"We have four-month cushions and eight-month cushions," says Ms Lee, expertly tying the four-month one around my five-month middle. I look vast. "There we are!" cries Ms Lee. "Marvellous!"

I try on a pounds 250 lime-green shift dress. It looks great. "Some women let themselves go, but you know there's no need to lose your fashion sense," Ms Lee says encouragingly.

However, even those who can be legitimately large (hooray) don't necessarily want to look like a house. "When I discovered I was pregnant I started on normal clothes, just in larger sizes," says 33-year-old Helen Bartram, 14 weeks down the line. "But I just felt so big and frumpy. It was dreadful." Helen looks doubtfully down at a pair of canvas trousers she is clutching. "I might feel a bit better in these."

We are standing in Formes, one of a rare breed of shops entirely devoted to worship of the bump. Somewhere between Harrods and Dorothy Perkins in price range, Formes, a French chain, is the sort of place from which you can happily march in smart working gear that accommodates your tummy without screaming life-long allegiance to the NCT, zipped bras or not.

As with all things familial (eg, children in restaurants), the French are far more fashionably positive about the whole issue. Formes, which has 28 branches in France, five in the UK and a mail-order section, is so keen on advertising funky fecundity that it sells stretchy cummerbunds to wear over leggings around your stomach.

"They're not ashamed of it," says Sarah Amigoni, company manager. "We even have a line in maternity wedding dresses, or, shall we say, dresses you can wear for a wedding."

Clearly well-heeled French mothers-to-be anticipate having a good nine months of it from the evidence of Formes' silk empire mini-dresses, boot- leg trousers and swimsuits without that ghastly mid-tummy ruching that cossies from the likes of John Lewis seem to specialise in.

"Not all women want to be changed utterly by the experience of being pregnant," Ms Amigoni says. "They still want to wear fashionable, normal clothes that are simply adapted for them."

And no boring fuss about dieting, either. What a pity it only lasts nine months.

Rosie Millard is the BBC's arts correspondent.

Formes UK: 0171 820 3434.