Nicole Johnson is showing off her baby bump. Olympic star Michael Phelps and his fiancée Nicole Johnson are expecting their first child together.

Johnson and Michael Phelps took to Instagram on Wednesday, Nov. 18, that they are set to welcome their first child - a baby boy.

Phelps posted a photo of him and Nicole in front of a swimming pool. He cradled her baby bump. Nicole wore a tee shirt and held a tiny underwear with "MP" written on them.

"We found out 8weeks ago we were expecting," Phelps captioned the photo.

"Today we're over 12 weeks and it looks like we're having a boy!!! #babymp #mp #lifeabouttochange #mpswim [photo] @djnolan5."

The former Miss California USA 2010 also shared the news on Instagram.

"Today marks 12 weeks and 5 daysof us having a little one and yesterday we learned we're having a BOY. Wecouldn't be happier!!" she posted.

The couple made the announcement that Johnson is 12 weeks pregnant with a baby boy.

Phelps, 30, has dated former Miss California Johnson on and off for eight years. Johnson stood by Phelps' when he checked into rehab after his second DUI arrest in 2014.

The 22-time medalist got engaged to Johnson, 29, in February.

"She said yes," Phelps wrote when he announced the engagement on Saturday, Feb. 21.

"I'm gonna be a Mrs. Phelps," the former Miss California , showing off the engagement ring.

Michael Phelps won 22 medals in his four summer Olympics. He won six gold in Athens, eight gold in Beijing and four more in London.

After a Sept. 30 bust, the swimmer faces charged of driving under the influence, excessive speed and crossing a double yellow line. He faces two years in jail.

That was Phelps's second DUI arrest since 2004. 

Michael Phelps first official public appearance since the DUI was to make a plea for swimmers and coaches to adopt safety guidelines to prevent Shallow Water Blackout.