Ashton Kutcher refuses to leave Mila Kunis' side as her due date approaches.

The 'Two and a Half Men' star, 36, has been spending as much quality time as possible with the pregnant 'Black Swan' actress, who is expecting a baby girl, recently and can't wait to meet their first child.

A source told E! News: ''Ashton is not letting Mila out of his sight. They are spending every moment together. He can't wait.''

The 31-year-old beauty isn't ''nervous'' about going into labour.

The insider said: ''Mila is so excited about the baby. She's not nervous at all. She's been really calm and chill about it all.''

The Ukrainian-born star is currently in nesting mode at their $10.2 million home in Beverly Hills and is doing everything she can to get organised for their unborn daughter's imminent arrival.

The source said: ''Right now she's just getting everything ready. She is making sure the house is prepared and the nursery is stocked. She's been very involved in everything. She really wants to be a hands-on mom.

''She is beyond thrilled that she's having a girl. She would have been happy with anything, but she is so excited that it's a baby girl.''

The couple, who got engaged earlier this year and started dating in 2012, are planning to get married after their baby's birth.