Jenna Fischer isn't prepared for her baby's birth.

The 40-year-old actress and her husband Lee Kirk, who married in 2010, are "getting close" to welcoming their second child into the world, but the brunette beauty is yet to set up the tiny tot's nursery and fill it with supplies.

She said: "There's nothing done. My mum and I got all the nursery supplies in order, so we have the appropriate number of onesies and diapers and a Diaper Genie -- but there's no décor. I just ordered a chair for my nursery and I'm very concerned that the baby is going to get here before the chair arrives."

Meanwhile, the star has been busy trying to prepare her two-year-old son Weston Lee for the upcoming arrival.

She explained: "He likes to talk a lot about what big boys can do and babies can't. Like, big boys can eat cupcakes and walk and talk, but little babies just sleep and eat and poop. We've been reinforcing the differences between a baby and a big boy so he can be excited about eating the cupcakes -- which he is."

Jenna and Lee have also been showing Weston cute photographs of when he was a baby.

She told People.com: "My big pregnancy craving with him was Menchie's frozen yogurt and there is a Menchie's across the street from where I delivered. After he was born, there is a picture of me eating Menchie's [and] holding him.

"We showed him the picture ... and I said, 'Mummy has to go to the hospital to get the baby out and you can come visit me.' He said, 'After the baby is out, Mummy gets to eat Menchie's.' I said, 'That's right ... do you want to come to the hospital and have Menchie's with me?'

"And he said, 'yes!'"