The Duchess of Cambridge was pretty in purple as she attended the Goring Hotel 's 105th birthday celebration in London today , but she 's not the first pregnant star to have sported the flattering Erdem frock . Back in September 2012 , Yahoo ! CEO Marissa Mayer , then eight months into her first pregnancy , wore a similar dress from the same Resort 2013 collection , which she had custom made by the London-based designer in honor of the San Francisco Symphony Opening Gala . Kate , 33 , who is seven months pregnant , wore the £995 ( $ 1,528 ) Darla design , which features three-quarter-length sleeves and ends just above the knees ; while Marissa , 39 , opted for a longer sleeveless variation which was better suited for evening wear . Scroll down for video . Maternity chic : The Duchess , 33 , who is seven months pregnant , wore a £995 ( $ 1,528 ) Erdem design , which features three-quarter-length sleeves ( L ) , while Marissa Mayer , 39 , opted for a sleeveless variation in 2012 ( R ) While Kate appears to have worn an off-the-rack version of dress , which is no longer available for purchase , Marissa was lucky enough to have been gifted a custom version in 2012 . 'My friend and brilliant designer Erdem made me a maternity gown for the opening of the SF Symphony tonight , ' the Wisconsin-born mother-of-one tweeted before the gala . Kate , who was pictured leaving the five-star London property at lunchtime today , wore her chestnut locks loose and teamed the dress with a pair of bespoke navy suede court shoes made by her favourite designer , Alexander McQueen , and a neat indigo clutch by Stuart Weitzman for Russell & Bromley . Stepping into spring : Kate appears to have worn an off-the-rack version of the dress ( L ) , which is no longer available for purchase , from Erdem 's 2013 Resort collection . Erdem Resort 2013 Darla dress in purple . Click to check out the current Erdem collection at Net-a-Porter ! Visit site . Well this is a nice surprise . We were n't expecting to see the Duchess of Cambridge today but here she is looking fresh as a daisy in a lovely floral print frock as she stepped out of the Goring Hotel . This spring-ready dress is by Erdem and is from the London based designer 's Resort 2013 collection . So not only is Kate rocking one of the coolest high end labels around but she 's still wearing regular fitting clothes , despite being seven months pregnant . How does she do it ? With fans in Alexa Chung , Kate Bosworth and Keira Knightley , Erdem is now a regular feature on the red carpet and Kate 's look today confirms just how into fashion she is . Styled with her favorite navy blue suede Alexander McQueen heels and a clutch by Stuart Weitzman , she 's the picture of elegance . And what you ca n't see is that the dress has a cute cut out at the back . Gorgeous ! Unfortunately it is no longer available to buy but if you click the link ( right ) you can take a look at the current collection at Net-a-Porter . For those who want to steal Kate 's style for less we 've found some pretty prints that will do the trick . L.K . Bennett 's 'Rosa ' dress is a dead ringer for the Erdem original or check out Coast and Marks and Spencer for similar styles . If the Duchess is dressing for spring then we 've all got the royal seal of approval . Coast Harla print dress . Visit site . Asos Maternity floral print dress ( now reduced to $ 41.50 ) Visit site . Little Mistress floral print dress at Asos ( now reduced to £56 ) Visit site . Sam & Lavi floral dress at Revolve . Visit site . Fond of purple : Marissa , pictured in February ( R ) , had a version of Erdem 's floor-length dress ( L ) custom made for her by the Canadian-born designer when she was eight months pregnant . Marissa , who is estimated to be worth more than $ 300million , opted for a small silver clutch and a set of statement earrings to accompany her maternity gown , and wore her blonde hair scraped up into a bun . The executive first revealed her pregnancy news on the very day Yahoo ! announced her hiring , and gave birth to her son Macallister on September 30 , 2012 , with her lawyer husband Zachary Bogue present . Canadian-born British-Turkish fashion designer Erdem Moralıoğlu , is known for his romantic and imaginative designs , which range in price from £390 ( $ 600 ) to more than £1,300 ( $ 2,000 ) . The label counts celebrity fans including Alexa Chung , Kate Bosworth and Keira Knightley , and has been a favourite of Kate 's for some time . Indeed , the English rose was regularly photographed wearing Erdem 's versatile designs while she was pregnant with Prince George , now one . Kate is due to give birth to her second child with Prince William , the Duke of Cambridge , in May .
The Duchess of Cambridge , 33 , wore a £1,528 ( $ 995 ) floral Erdem dress today in London , from the designer 's 2013 Resort collection . Marissa Mayer , 39 , wore a custom variation of the same dress to a San Francisco event in September 2012 .