Courtney Stodden and Doug Hutchison are eagerly awaiting their first child together.

The 21-year-old reality star took to Instagram on Sunday to wish her 56-year-old husband, Doug Hutchison, a happy first Father's Day, and also flaunted her growing baby bump in an itsy bitsy, teeny weeny pink polka dot bikini.

WATCH: Courtney Stodden Shares Candid Morning Sickness Pic -- 'When Does This End?'

"Happy first Father's Day to my amazing hubby! #fathersday #babyontheway," Stodden captioned the shot.

Last week, Stodden posted another picture of herself in the same bikini, and spoke out in defense of her baby bump.

"Stop fat shaming pregnant women. Honestly," she captioned the snap. "If our society thinks that it's actually ok to say a pregnant woman is 'fat' there's something seriously wrong with it."

Stodden announced she was pregnant with the controversial couple's first child last month.

"I feel happy about it but extremely overwhelmed," she admitted to ET. "I'm going through a lot at the moment. This wasn't a planned pregnancy. But life happens."

Still, her relationship with Hutchison remains strong. The two recently renewed their wedding vows at the Hollywood sign in Los Angeles to celebrate their five-year anniversary.

"Today marks my 5th wedding anniversary," she wrote on Instagram last month, sharing a picture of her hubby carrying her on their wedding day in 2011. "Five years ago I married an incredible man & we are celebrating by renewing our vows in a very special place!"

WATCH: Pregnant Courtney Stodden Embraces Her 'Insane Body Changes' With Bikini-Clad Dance Session