Meghan's maternity and the fashion brands hoping to strike gold

Meghan wore a dress by Australian designer Karen Gee as she arrived in Sydney on her first overseas tour

The Duchess of Sussex's first outfit after announcing her pregnancy has sparked an online shopping frenzy.

The website of the Australian designer Karen Gee crashed as it was flooded with new customers looking for the £975 ivory "Blessed" dress

Ms Gee said she was "thrilled" to see Meghan wearing her design.

"We didn't know she would be wearing the Blessed dress on the first day of the royal tour - it was a wonderful surprise," she said.

"The response has been absolutely overwhelming and the website was inundated yesterday.

"We are feeling blessed to have had such a great amount of interest even if it means fulfilling orders all night."

• Why the fashion industry loves Meghan Markle

• Meghan: From actress to duchess

Ms Gee said the dress had attracted attention across the world, with strong sales in the US, the UK and Dubai, as well as Australia.

Celebrity stylist Alex Longmore said Meghan's American links could mean her influence on the international market will be even greater than her sister-in-law Catherine, the Duchess of Cambridge, had when she was pregnant with her first-born child, Prince George.

"The impact won't just be in the UK, it will be in America too. Retail power in America is huge," she said.

Ms Longmore recalled being told by one British designer that, when Meghan wore one of the brand's bags, the designer received calls from numerous American retailers wanting to stock it.

Cecile Reinaud, founder of maternity brand Seraphine, has experienced the royal effect first hand.

The Duchess of Cambridge wore the brand several times during her three pregnancies and each time the items of clothing quickly sold out.

Catherine (right) wore a Seraphine dress during her first official appearance with Meghan in February

"When our clothes are worn by royals it's always been good for sales and raising the profile of the brand internationally," Miss Reinaud said.

"In pregnancy in particular there's an even greater focus from the media. I think Meghan will have a similar effect."

JoJo Maman Bebe had a similar experience when Catherine wore the maternity brand's Cream Princess Coat while pregnant in 2015. The coat sold out instantly.

The brand's founder Laura Tenison said: "It is really exciting to hear Meghan is pregnant. Her style is effortlessly cool.

"As a global modern woman, she is not afraid to experiment with fashion and that could mean she will wear more contemporary, edgy maternity wear."

Kate Middleton wore this coat by JoJo Maman Bebe several times while pregnant with both Princess Charlotte and Prince Louis

But Ms Longmore says that Meghan, in contrast to her sister-in-law, is unlikely to be showcasing high street brands within the budget of ordinary shoppers.

Despite the excitement caused when she wore a £45 Marks & Spencer jumper earlier this year, Meghan has tended to have more expensive tastes than Kate, who was famously seen in a Topshop dress during her pregnancy.

"The High Street is Kate's thing. I don't think Meghan's ever been a High Street girl," said Ms Longmore.

She predicted that, during her pregnancy, Meghan would stick to her favourite designers, such as Givenchy, who designed her wedding dress.

Meghan caused a stir when she wore an M&S jumper for a visit to a community radio station in Brixton, south London

But this doesn't mean she won't still influence the High Street.

"Her clothes are very wearable. They might be expensive but they are pretty easy to emulate," said Ms Longmore.

She said Meghan's trademark looks, including tailored jackets, oversized shirts and autumnal colours could all be picked up for a fraction of the price on the High Street and also translated well to maternity wear.

"I imagine given her petite form she will probably carry on with a similar style," said Ms Longmore.

"She's going to wear lines that flatter her and maybe show off her bump. I don't think we'll see a huge change in her style but an adaption."

Meghan is a fan of tailored outfits and shirts

Ms Tenison agreed Meghan's style was still likely to influence more affordable brands like her own and said major retailers would be "watching her closely" to bring her style to their customers.

And the interest isn't likely to end when her baby is born.

All eyes will then be on what baby clothes, pram and other infant accessories the duchess might go for.

The Queen's granddaughter Zara Tindall recently became an ambassador for iCandy pushchairs and appeared alongside her three-month-old daughter in an advert for a buggy costing £1,500.

As Mrs Tindall does not have a royal title, she faces fewer restrictions on forging commercial partnerships. Meghan, as a duchess and wife of a prince, is unlikely to follow her lead.

So baby brands may not be securing lucrative sponsorship deals any time soon, but Miss Reinaud said they would still be looking to tap into Meghan's global influence.

"Whether [she is] pregnant or not, every designer is watching her."