Ryan Reynolds 'traumatised' by baby's fever test

New father Ryan Reynolds has been left scarred after having to stick a thermometer up his sick daughter's butt to take her temperature.

The Green Lantern star reveals baby James kept the actor and his wife, Blake Lively, up all night on Sunday (20Sep15) as she struggled with a fever, and the new parents had to call on their paediatrician for help.

Reynolds admits he and his wife were left mortified after being instructed to prod the child's bum.

During an appearance on morning show Live with Kelly and Michael on Monday (21Sep15), Reynolds explained, "She didn't sleep last night, first fever... How I found out was that I needed to check her temperature through the rectum, which for me was just so traumatising.

"I was like, 'No, it can't be! There's a mouth, there's an armpit, there's got to be something'. The doctor was like, 'No, no, no, just have one of you guys distract her and then do it, she'll be fine...'

"You can't distract her from that! I warmed it (thermometer) up and everything... And so I did that. It was terrifying though. It all went well though, I didn't lose it, it came back out. You just can't help but think that this is gonna leave a lasting mark...! They've gotta come up with a better system, seriously."

Despite the overnight trauma, Reynolds insists he has no problem with fulfilling his duties as a dad and the responsibilities have helped ease his own temper tantrums.

He tells GQ.com, "I'm surprised how patient I am with it. I feel like I could sometimes have a bit of a short fuse, but there's just been this weirdly endless supply of patience. I have no problem waking up five times in the middle of the night and changing diapers, and as exhausted as you get, I have this stupid grin on my face all the time. And that's not because I have a nanny or something like that. It's just us right now, and I love it."