Rose Byrne's breast milk was confiscated by airport security.

Speaking on 'The Late Show With Stephen Colbert', she explained: "I've been taking my breast milk everywhere with me. They wave this weird thing over the top of it and there's a whole production going on. They take it very seriously that it could be something. I just stand there and smile and tell them that it's really breast milk and that it's nothing."

When the host suggested that all she needed to do was point to Rocco, she quipped she just needed to say: "He's really real; he's here. You want me to get 'em out? What do you think?"

However, she quickly added: "I'm not going to do that. No, no, no!"

Along with running into difficulty with air travel, Rose admitted she even finds it hard just leaving the house these days because babies need so much stuff.

She said: "It takes a long time to leave the house, maybe an hour, hour and 45 minutes just to get out the door. To do anything, you have to bring so many things with you: the bottle, the sling, this and that. Then when you get out, then he just throws up everywhere or takes a big poop, and you've got to go back inside again."

Meanwhile, 'Vinyl' actor Bobby is already a father to 21-year-old son Jake - who he has with ex-wife Jenny Lumet - and Rose is thankful the actor has previous experience to draw on and help guide her in caring for Rocco.

She previously said: "Bobby is terrific. He has a 21 year old so this is old hat to him. And I have to say, having someone who's already a parent is great because this is all very, very new to me. So I'm just taking tips from him."