The 37-year-old reality star and the 'Gold Digger' rapper already have North, five, and Saint, two, who were carried by Kim, as well as seven-month-old Chicago who was born via a surrogate mother after Kim was warned against getting pregnant again.
And despite only welcoming Chicago into the world earlier this year, the couple are reportedly already talking about expanding their brood once more.
A source said: ''They have absolutely talked about trying for another baby with the help of a surrogate, but nothing seems decided for sure. Chicago is still little, and they have time.
''They don't seem to be in a huge rush. They would use the same surrogate if she agrees to help them again. Kim can't say enough kind words about the surrogate.''
The 'Keeping Up with the Kardashians' star and her 41-year-old spouse have reportedly been thinking about baby number four since Chicago was only ''a couple of days old''.
A second source told People magazine: ''Kim and Kanye were already talking about baby No. four when Chicago was just a couple of days old. And they absolutely would use the surrogate again. They love her.''
The news comes after Kim recently revealed that whilst she's open to the idea of having another baby, she hasn't decided anything just yet. Asked if she and Kanye are planning a fourth child, she said: ''I don't know. I don't know. I read something that it was, you know - none of that was true.
''But I've been really open about it and talked about it on our show, so I don't know.
''We start filming season 16 next week, so if I think about it more and it's gonna happen, you'll definitely see it on the show.
''But as of now, no.''
Kim's doubts about a fourth baby come just a few months after she said she'd love to have another because she really ''enjoyed'' using a surrogate with Chicago.