(Credit: Séraphine | TRH The Duke and Duchess of Cambridge 2013)

The maternity dress worn by Kate Middleton, the Duchess of Cambridge, in her latest photo with the royal baby and Prince William sold out within hours of the release of the family portrait.

The new mother was seen previously in fashion by British company Séraphine, shopping in the brand's "Renata" polka dot dress, which retails for $79, when she was still pregnant. Three weeks ago, the new mother was photographed arriving at her parents' home wearing Séraphine's blossom knot front lavender dress.

Cecile Reinaud, founder of Séraphine, said she was honored, once again, that the duchess chose her company's fuchsia knot front dress, which retails for $79, for the official family photograph.

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The company's customer A-list includes Angelina Jolie, January Jones, Jessica Alba, Jennifer Garner and Kate Hudson, but none seem to have attracted the same viral attention as images of the duchess.

Images in the media showing Kate wearing these dresses have led to a spike in Séraphine's sales of over 100 percent in July, the company says, and the dresses sold out within hours of the photos being distributed.

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"We heard rumors online that an official royal family photo was going to be released imminently, so we were on the look out to see what her next outfit would be and hoped it would be Seraphine," she said. "We saw the picture go live online overnight and are absolutely honored and so happy to see her in another one of our dresses!"

The company touts the dresses worn by Kate on its website, stating the tag-line "as worn by the Duchess of Cambridge," and the advertising seems to be working. There are waiting lists that are expected to last for weeks for customers hoping to buy the same dresses. When ordering the fuchsia dress, the website informs patient customers: "Due to high popularity of this style, please be advised that orders will be dispatched week commencing 16th of September."

The 10-year old company owns stores in London, with retail partners around the world, while the website serves customers in over 20 countries, including the U.S.

Though many companies have tried to capitalize on the "Kate effect" marketing goods related to her pregnancy, only a handful have been able to market from the few public appearances of the royal family since the "royal birth."

The first public appearance of Prince George leaving the hospital in a swaddled blanket led to the website crash of the blanket manufacturer, aden + anais of Brooklyn, N.Y.

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