Kim Kardashian has revealed her first pregnancy was a big surprise.

The reality TV star tells Billboard she wasn't ready to become a mom when she learned she was expecting her daughter North, but she's thrilled the little angel and her brother Saint chose her and husband Kanye West as their parents.

Kim explains, "We weren't trying (to have a baby) or planning on it and I just didn't think I was ready. But you're never ready. It happens when it's supposed to happen and at the right time.

"Both times when I was pregnant I'd literally just pray, 'I hope my baby can handle this life'. I believe their souls choose us to be their parents - that they choose this life. That's my belief."