"Saks Fifth Avenue always strives to meet the needs of our customers. After recent review, we concluded there are customers who desire designer clothing in sizes that are not currently available in our stores," the company said in a statement.

Saks has for years had its Salon Z department, which caters to plus sizes, but this new initiative targets ripped-from-the-runway looks from the likes of Oscar de la Renta and Carolina Herrera, and will include larger sizes within designer departments.

Adding larger sizes, especially for designers who sometimes don't sell anything larger than a 10 or 12 in their own boutiques, is a considerable commitment, said Sasha Iglehart, deputy fashion director at Glamour. "It's a real investment for these brands to make sizes in that range. It's not just taking a pattern and making it bigger," she said. "The proportions are different, and there has to be real thought into what's flattering to women in that size range."

"I hope this inspires other retailers and designers," Iglehart added.