Ashton Kutcher and Mila Kunis Are 'Incredibly Excited' for Their Daughter to Arrive

Mila Kunis and Ashton Kutcher

FameFlynet

09/19/2014 AT 05:50 PM EDT

It could happen any day now!

Ashton Kutcher and Mila Kunis are waiting with bated breath for their baby girl to arrive, and like any expectant parent, the actor is filled with a mix of excitement and anxiety.

"He is a nervous wreck," a source tells PEOPLE. "They were hoping the baby would come this week because he's on hiatus [from his show Two and a Half Men].

So far no luck, which leaves Kutcher, 36, and Kunis, 31, waiting for their bundle of joy while continuing with their usual routines.

For Kunis, that includes going to yoga classes and taking walks around her neighborhood.

And though Kutcher has been doting on his fiancée, he did take some time out – perhaps to shake off some of those nerves – for a birthday party Thursday night.

After possibly alluding to his pre-baby jitters on his Twitter account earlier in the day ("Nervous is excited's victim sister," he wrote), the soon-to-be father stepped out to celebrate his pal Richie Akiva's birthday at 1OAK that night where he hung out with Jamie Foxx, Robin Thicke, Diddy and Jason Derulo.

"He is incredibly excited for the baby," says the insider. So is Kunis, of course. "Mila just wants the baby to come out already!"