Jessica Simpson shows off bare baby bump in bikini picture

Behold: Jessica Simpson's baby bump!

The hot mama revealed her expanding belly for the first time in a candid self-portrait from her hotel bathroom in Hawaii, where she's vacationing with her family.

"Bumpin' and Proud!" tweeted the fashion designer Sunday (Dec. 30), sporting a colorful bikini and matching cover-up (though it's not covering up much in this snapshot).

Simpson and her fiancé, Eric Johnson, haven't yet announced the due date for their second child, but their 8-month-old daughter, Maxwell Drew, is apparently very excited about being a "big sis."