How disturbing that Spanx for pregnant women are now a maternity must-have With celebrity endorsements, sales of pregnancy shapewear are soaring Control underwear is many women's secret weapon But should expectant mothers squeeze into it because it's fashionable? And could Spanx affect an unborn baby's wellbeing? By Thea Jourdan Holding it all in: But are control pants good for mums-to-be? The night before my third child was born sticks in my memory for all the right reasons. My husband and I had decided to get a babysitter and head out for a romantic dinner a deux, a last hurrah before the baby arrived. As he waited for me to get ready, I pulled on my comfiest pair of granny knickers and a stretchy, maternity bra. Admiring my vast bump in the mirror, I then slipped into an empire-line dress which emphasised my full curves. Happy with what I saw - and proud as punch of my bump - I headed out of the door, arm-in-arm with my husband, who told me, lovingly, that he thought I looked like a ship in full sail. I wasn't remotely offended: he was right, and I felt wonderful. That night, in 2009, it never occurred to me to worry about my wobbly bits. I never once considered whether I had a sleek silhouette or pert behind. I was in a blissful state, thrilled to be nurturing a new life, feeling free of all the usual constraints of fashion. How times have changed. Now the cellulite police have turned their attention to pregnant women. Where expectant mothers could once let it all hang out, they are increasingly expected to look svelte even in the latter stages of pregnancy. And how is this to be achieved? With maternity shapewear, which lifts bottoms and smoothes out hips and thighs while supporting the lower back and tummy. Pregnancy shapewear is fast becoming a maternity must-have - available in every shape and size for women who feel they need extra help from their underwear to smooth, enhance and reshape what lies beneath. Since the most successful brand, Mama Spanx, was launched in the UK in 2011, sales have soared. M&S and Debenhams have their own lines of maternity shapewear, and Primark offers a budget version. And in online chatrooms and maternity blogs, pregnant women seem delighted that they can squeeze themselves into the human equivalent of a sausage skin. Why is utterly beyond me. As someone who has carried three children, the most important thing when it comes to what to wear during pregnancy is good old-fashioned comfort. Not so for a happy Spanx customer, however, who wrote a glowing online review of the Power Mama Maternity Shaper, a £28 nylon and Lycra body suit extending from below the breasts to the knees. She writes: 'They are easy to put on. I was worried that it'd be a struggle. No tell-tale visible pant lines and no band at the bottom of the leg so you don't get the mark under clothing where the shaper finishes. Red carpet-endorsement: Both TV presenter Amanda Holden (left) and Danii Minogue have extolled the virtues of control underwear I put them on and the effect was quite dramatic. I lost the saddlebag hips I seemed to gain during pregnancy and they smoothed my bottom into a rounder, perkier shape. You feel supported all round without feeling squashed. I wanted a smoother shape under a jersey maternity party dress -these do the job. Control underwear may be many women's secret weapon, but should we really be expecting pregnant women to squeeze themselves into it simply for the sake of fashion? Spanx founder Sara Blakely insists she designed her maternity range to first and foremost provide comfort. 'The fact they make your bottom and thighs look less jiggly and more toned is a side benefit,' the U.S. businesswoman argues. But the pregnant woman on the Spanx packet looks far from comfortable. Photographed wearing a nude pair of maternity control pants and towering stiletto heels, she looks rather like a pregnant pole dancer. She is also, disconcertingly, headless, since the picture is cropped just above the breasts. 'Control underwear may be many women's secret weapon, but should we really be expecting pregnant women to squeeze themselves into it simply for the sake of fashion?' So how did this trend for maternity corsetry start? As with so many other bonkers trends, it began on the red carpet. TV presenter Amanda Holden, 42, credited Spanx with allowing her to hide her pregnancy from photographers for six months. Similarly, Dannii Minogue, also 42, extolled the virtues of control underwear, wearing it to firm up her behind when she was expecting her son, Ethan. In many ways, Amanda and Dannii may be typical of the maternity shapewear fan base - older women who need a little more help when it comes to sagging bottoms and dimpled thighs. However, I can't help but wonder if the fact that they were older when they conceived meant they felt uneasy with the appearance of a generous bump after so many years of being red-carpet ready. Can maternity shapewear affect an unborn baby's wellbeing? 'Babies are safely cocooned in the womb,' says London-based consultant gynaecologist and obstetrician, Dr Mike Bowen. 'It's going to take a lot more than support hosiery to cause them even mild irritation.' However, the National Childbirth Trust takes a more cautious approach. NCT policy adviser Elizabeth Duff says: 'It is important not to restrict blood flow anywhere in the body during pregnancy, as the growing baby needs the oxygen that is supplied through the increased blood volume in expectant women. 'Any woman considering wearing tighter clothes for support is advised to talk to her midwife before investing in this kind of shapewear,' she adds. The physical difficulty of removing constricting shapewear could cause other problems, according to Gail Johnson, a midwife and education adviser at the Royal College of Midwives. She tells women to embrace their natural pregnancy shape instead of trying to constrict it. Soaring sales: Mama Spanx is the most successful brand - but maternity shapewear could affect an unborn baby's wellbeing 'Anything that encourages pregnant women not to go to the toilet when they need to is likely to cause problems and increase the risk of urinary tract infection,' she says. If a woman's pregnancy reaches its third trimester in the summer months, she can expect to feel rather overheated in high-control underwear. There is also the troubling issue of muscle wastage: a garment that supports your stomach and bottom all day, every day, will take the load away from muscles and ligaments. London-based physiotherapist Sammy Margo, a spokeswoman for the Chartered Society of Physiotherapy, explains: 'What I say to my patients is "use it or lose it." What we find is that women who wear maternity shapewear when they have no physical need can weaken muscles in their bottoms, stomachs and lower backs. 'After the birth of their baby, they are more likely to be injured as they lift and care for their newborns' she warns. It's perplexing that so many women are relying on maternity shapewear when pregnancy fashion has never been better. For thanks to High Street trailblazers such as JoJo Maman Bebe and the Duchess of Cambridge's favourite maternity clothing store Seraphine, it is perfectly possible for expectant mothers to look stylish in maternity wear. The trendy outfits make a feature of a bump without the need for shapewear. Fashion stylist Tamara Cincik, whose celebrity clients include singer Christina Aguilera and top models Lily Cole and Daisy Lowe, says pregnant women should be confident in themselves whatever their shape - but there is one piece of maternity lingerie which she says is absolutely vital. A good-fitting bra is important and needs to be resized regularly. I would recommend women are measured for their bras regularly over the course of their pregnancy and afterwards when they're breastfeeding.' Above all else, women shouldn't be made to feel insecure about how they look during the swingeing physical changes that come with pregnancy. And they certainly shouldn't feel some kind of imperative to be teetering around on heels in underwear that is hot, tight and uncomfortably restricting. I for one would be a lot happier if that Mama Spanx model kicked off her stilettos and shapewear and slipped into some roomy PJs and a comfy pair of slippers.