And there is no doubt that the couple - who already have two year old daughter Wyatt Isabelle together - will pick an unusual moniker for the little boy as Ashton previously revealed he wants to call him Hawkeye.
Mila Kunis welcomes second baby. PICTURE: Reuters/Mario Anzuoni
He said: "There was a rallying cry from a collective that believed in the name Hawkeye. Hawkeye Kutcher, it didn't fly, it didn't cross the Mila threshold, it came to the threshold but it got knocked out. You don't want everyone else's opinion on the name. When we get in the naming process she hates every name I come up with."
Meanwhile, Mila previously admitted she has become incredibly selfless since she became a mother.
Asked how she's changed since becoming a mom, she said: "It changed everything. It gave me a really interesting sense of confidence. My priorities shifted and I think I became incredibly selfless.
Knowing that I was going to have a baby made me be like, I have to give up so much of myself and I'm happy to do that. It wasn't like, oh I'll sacrifice. It was more, I want to do this.
"It makes you pick projects differently. In my twenties I had nothing to lose. I was travelling the world, working non-stop and I was like, life is great, because I didn't have a home to come back to. Then all of a sudden I had a husband and child and wanted to be at home with my family."