Pete Wentz finished an interview early after hinting he and his pregnant wife, pop star Ashlee Simpson, are expecting twins.

The Fall Out Boy rocker accidentally let the news slip during an interview on a US radio show when he referred to his unborn baby as "them".

Pete said: "We've been keeping a book so far, like a journal for them - for them when they're, uh, born."

The 29-year-old musician then started laughing nervously before wrapping up the interview.

Meanwhile, Pete has also revealed he is keen to find out the sex of the unborn child, or children.            

He said: "I'd like to know the sex of the baby. It would be a bummer if you bought a boy a bunch of pink stuff!"

He also revealed 23-year-old Ashlee is coping well with the pregnancy, adding to In Touch Weekly magazine: "I think any pregnant woman knows it's a lot of stress on your body, but she's really healthy and handling it like a champ."

Pete and Ashlee married in May after dating for two years.//Bang! Showbiz//Reuters