Pregnant Kate Middleton stepped out in a budget-friendly $50 maternity dress by ASOS on Wednesday, Mar. 18 -- and it's already sold out! Credit: REX

Thrifty and thriving! Duchess of Cambridge Kate Middleton proved yet again on Wednesday, Mar. 18, that she can make anything look luxe.

Prince William's pregnant wife, 33, stepped out for her visit at the Brookhill Children's Centre in Woolwich in East London in a polka-dot maternity dress by ASOS, a breezy black-and white skater style that retails for just $63.

While her retail look made initial headlines, the Duchess also shared some special baby news during her visit on Wednesday. Us Weekly can confirm that Middleton disclosed the due date of her second baby — marking the first time that she's shared it publicly.

Christine Osborne, a volunteer at the charity, first asked the Duchess when the baby would be born. "I’m due mid-April to the end of April," Middleton replied. "Not long to go now."

Osborne, a grandmother who's worked for the Home-Start family support charity for seven years, told Us and other reporters: "I couldn’t resist asking! It’s very exciting — and it was wonderful to have her here."

As for the Duchess' dress? The bad news is that less than one hour after her appearance, the dress in both the 3/4 sleeve and the short-sleeve version was already out of stock online. ASOS, however, told British outlets that the (new!) dress will be restocked by next week. The Duchess is, of course, no stranger to relying on the print during her pregnancies.

This past March, she recycled the Dalmatian-print Hobbs coat that she first slipped on while pregnant with Prince George, 19 months. During her first pregnancy, she caused quite the "Kate Effect" after wearing a polka-dot Topshop maternity dress in April 2013 while touring the set of Harry Potter.

The Duchess brought a refreshing dose of originality to the look by accessorizing the piece with black pumps, silver jewelry, and a tiny black clutch. Unlike her updo hairstyles she's worn for recent engagements, Middleton’s trademark brunette tresses were blown out in a sleek, voluminous hairstyle.

Similarly Middleton's appearance on Wednessday was far less bundled up than her time at the St. Patrick's Day parade hosted in Aldershot, England the previous morning. Middleton beamed in a bespoke coat by Catherine Walker, which she accessorized with suede heels, and a chocolate hat and gloves.

Tell Us: What do you think of Middleton's thrifty new look? Tweet with @UsWeekly using the hashtag #stylebyUs!