Kim Kardashian West decided to have another child because she ''missed having a baby in the family''.

The 'Keeping Up With The Kardashians' star and her husband Kanye West are reportedly set to welcome a third child into the world via a surrogate and the pair made the decision because Kim thought her two kids - North, four, and Saint, 19 months - were growing up too fast.

A source told People magazine: ''After having Saint, Kim was told she couldn't carry another baby - that it would be too dangerous - and she was okay with that. She was content with two. But even after having Saint and knowing everything, Kanye was already talking about having more kids. He would want a family of five or six if it was up to him.

''Kim was never going to let herself get pregnant again. But she thinks her kids have grown up too fast and misses having a baby in the family. Things have been good for the past few months, and she started agreeing with him [about having another child].''

Meanwhile, Kim and Kanye are said to be ''very happy'' together now they are set to expand their brood.

A source shared recently: ''Kim was never going to let herself get pregnant again. It's just too dangerous for her. Kanye was initially the one pushing for baby No. 3. They are both very excited to give their kids a sibling. Things are great between them. They act very happy together.''

And Kim hasn't been short of offers for a surrogate as her mother Kris Jenner and her sister Kourtney Kardashian have both thrown their name in the mix.

However, it is believed the couple have opted for someone outside the family, who they think is ''perfect'' to carry their child.