Chicago Fire star Jon-Michael Ecker has announced he’s set to become a dad.

The actor shared an adorable picture of his wife Laura James cradling a baby bump, announcing they are expecting their first child together.

“In this big book of life, this has to be one of the most exciting… and scariest chapters,” he captioned his Instagram picture.

“Gonna have to start spending less on sandpaper and more on diapers. Not sure how @lauraellenjames does it but just 4 months to go.”

He also posted a sweet sonogram picture, showing their baby giving a thumbs up.

Laura, who married the actor in October last year, replied: “Love you. You’re going to be the best dad.”

She also posted a few pictures of her stomach on her own social media, alongside an ultrasound snap.

“5 months with you. We can’t wait to meet you,” she wrote.

Ecker joined Chicago Fire in season 9, playing Fire Lieutenant Greg Grainger. His character instantly became a fan favourite, but left later the same season.

The show’s co-creator and co-showrunner Derek Haas said he’d like to see Greg return, previously telling TVLine: “I really like him. I would definitely want to see him again.”

Fans of the show will be seeing a familiar face returning in the form of Matthew Casey, with original star Jesse Spencer returning.

It’s reported he’ll be back later in season 11, but details of his return are being kept under wraps.

It follows Taylor Kinney taking a leave of absence from the program to deal with a personal matter, with character Kelly Severide leaving to take part in an arson investigation training program.