Jessica Simpson Posts Revealing Twitpic

By Marla Lehner

12/27/2012 at 04:55 PM EST

Jessica Simpson is pregnant and proud to show it.

The expectant star – who is vacationing in Hawaii with her fiancé Eric Johnson, their 7-month-old daughter Maxwell Drew and other family members – posted a revealing photo of herself smiling and clearly enjoying the laid back lifestyle of the islands on Thursday.

"Fun in the sun," Simpson, 32, wrote to accompany the Twitpic, which shows the star wearing her sun-kissed blonde hair loose and dressed in a red beach frock and a cowboy hat.

Simpson hasn't been shy about sharing her happiness on Twitter over the holidays. On Christmas Day, she revealed the news of her pregnancy by sharing a picture of her daughter with the words "Big Sis" written in the sand in front of her. And on Wednesday, Simpson posted a shot of herself grinning with Johnson on the beach.

RELATED: Pregnant Jessica Simpson Walks on the Beach in Hawaii