"It is an immense honour that the Duchess chose a Seraphine dress for her official family photograph," Seraphine founder Cecile Reinaud told HELLO! Online.
"It's a dream come true to see that she likes my designs so much that she continues to wear them after the birth of Prince George. I was delighted to see her three weeks ago in our Blossom dress and today she looks so radiant in our bright fuchsia design, it's a perfect choice to show the world her happiness with her newborn and husband."
The brand also described how Kate's royal stamp of approval has affected the brand's sales. Since she was spotted sporting the Blossom dress to leave Kensington Palace and travel to Bucklebury with her newborn baby, sales have increased more than 100%.
Both dresses were sold out within hours of the new mum being pictured in them and an eight week waiting list quickly built up for customers eager to purchase the same dress.
"The Kate effect is worldwide, from China, Russia or South Africa, sales are boosted due to her pregnancy and by the fact that she chose to wear our brand," said Cecile.
Seraphine registered an annual turnover of £5.2million in the year ending March 2013, but is expected to rise above £8million by the next financial year.
Kate was also a fan of the brand during her pregnancy - she was spotted wearing Renata polka dot dress and white Colette maxi skirt.