In the selfie she shared, she's wearing a bikini and showing off her baby bump.
The superstar couple's daughter was born on September 21, 2016.
"I have a daughter, I have the most attractive wife in the entire world", he said later at a Hollywood Star event.
"I am one of the luckiest people who's ever lived and it has nothing to do with me".
"Adam and Behati are so happy to be adding another baby to their family", a source tells PEOPLE.
"I love Adam, and when you get married and you fall in love with someone, you think that there's no greater love than that love", she added at the time.
Behati revealed in an interview with Access Hollywood earlier this summer that Adam is an awesome parent to Dusty, and they would love to expand their brood. "And then you have a baby, and it's just next-level love". "They are in love with Dusty and can't wait to make her a big sister".