Shiri Appleby Credit: Courtesy of Shiri Appleby/Instagram

Countdown to baby! Shiri Appleby shared a photo of her bare baby bump in a bikini shot on Instagram Friday, March 1. The Girls guest-star and Chicago Fire actress, 34, is expecting her first child with fiance Jon Shook any day now. "T minus 20 days," the pregnant star captioned the shot.

In the stunning photo, Appleby proudly shows off her growing bump in a green string bikini while posing for the camera on the beach. Appleby and Shook, who become engaged during a July 2012 trip to Ventotene, Italy, have decided to keep the gender of their baby a surprise.

"He really wanted to do it and it sounded like fun," the actress told Us Weekly of her fiance, a chef at L.A.'s Animal. "It's really made the whole pregnancy a heightened excitement because you just don't know what it's going to be!"

Appleby celebrated her baby shower on Jan. 27 and her fiance's eatery with about 50 of her female friends. The mom-to-be told Us that her pregnancy has brought her even closer together with Shook.

"When you see this guy going to all the doctor's appointments with you and you tell him you're feeling a certain way and two minutes later he's looked it up on the Internet to tell you that it's normal, you realize that you're really starting a family with somebody," she told Us, "and it's just -— there's no way to look at that person and not be more in love."