Kim Kardashian West has confirmed she and Kanye West are expecting their third child via a surrogate.

The 36-year-old reality star - who already has four-year-old daughter North and 21-month-old son Saint with her husband - has confirmed after weeks of speculation that her family is set to expand yet again with the help of a surrogate mother, after being warned against getting pregnant again due to complications from her previous two deliveries.

In a promotional clip for the upcoming season of 'Keeping Up with the Kardashians', Kim makes the confession whilst on the phone to her sister Khloe.

She said: ''What happens every time I say, 'Guess what?'''

To which 33-year-old Khloe - who is also rumoured to be expecting her first child with boyfriend Tristan Thompson - responds: ''The person's pregnant?''

And Kim then excitedly exclaims: ''We're having a baby!''

The confirmation comes just weeks after Kim previously insisted she and Kanye had ''never confirmed anything'' about the growing speculation that their surrogate was indeed pregnant.

She said recently: ''I've definitely seen a lot of things, we've never confirmed anything. So, I think when we're ready to talk about it we will, and I think it's super invasive when people are just ... So many details out there, and like I've never heard this, I've never heard this. Like whatever. We have not confirmed it, and that's that. I'll let you know when we're ready.''

Previously, it was reported that Kim and Kanye, 40, will become the proud parents of a baby girl when their surrogate gives birth in January.

The unnamed woman was reportedly hired to carry their baby for $45,000, which would be paid in 10 equal instalments. It was also agreed the woman would receive an extra $5,000 per child in the event of a multiple pregnancy and an additional $4,000 if she lost reproductive organs in the process.