Nicole Richie will let fate decide how many children she has.

The 27-year-old star's boyfriend Joel Madden - who recently announced the couple are expecting their second child - is unsure how big their family will be because they don't have a baby making schedule.

He said: "We let love plan our babies. We said even before this one that we didn't know how many kids we were going to have - then we got pregnant!"

The Good Charlotte frontman - who has a 14-month-old daughter Harlow Winter with Nicole - says his mother was the first to suspect Nicole was pregnant again.

He told KIIS FM radio host Ryan Seacrest: "My mom called me and she's like, 'Is Nicole...?' Every time, I'm like, 'Mom, come on, seriously. I would tell you.' And then I swear, two weeks later it comes true. But we're excited about it. It's going to be great."

Joel has also revealed he finds it difficult leaving Nicole and their daughter behind when he tours with his band.

He explained: "That's hard man, when you leave your kids and they're saying no. I wrote a song for Harlow."