Reality star Kim Kardashian was shocked to learn she was pregnant with Kanye West's baby while she was meeting with infertility specialists.

The rapper announced the couple was expecting a baby last month, and the mum-to-be admits she was pleasantly surprised when she heard the news - since doctors told her she might have trouble conceiving, just like her sister Khloe Kardashian.

During an appearance on the Today show, she said, "It's kind of a miracle that I did get pregnant... I know Khloe has been very open about her fertility issues and I think I was always really kind of quiet about mine - and I have similar issues.

"So it was a pleasant surprise when so many doctors were telling me one thing and then the opposite happens. And that's just an exciting moment, you can't plan for things like that. I think it's just such a blessing knowing my circumstance... The best surprises just happen when you don't plan."

The 32 year old, who is due in July, is still legally married to her basketball star ex Kris Humphries, but she isn't ruling out walking down the aisle with West when their divorce is finalised.

She added, "(Marriage is) something that we (West and I) talk about, but I think just right now (we're) focusing on the baby."