Kim Kardashian West found it ''tricky'' choosing to have another baby girl.

The 'Keeping Up With the Kardashians' star and her husband Kanye West used a surrogate to carry their third child, Chicago, now 12 weeks, because of complications Kim had had in her previous pregnancies, and she has admitted it was difficult selecting which embryo to have implanted, but ultimately decided on a female as doctors told them the fertilised egg was the ''healthiest''.

She said: ''It's a really tricky thing. What sex do you put in? I just said, 'Which one is the healthiest? Pick the healthiest one,' and that was a girl.''

The couple - who also have North, four, and two-year-old Saint - worked with agencies to interview potential surrogates and knew immediately when they had found the right person.

Kim told the new issue of America's ELLE magazine: ''I refer to her as a surrogate, but it's completely my and Kanye's DNA, so technically that's called a gestational carrier. A surrogate is when they use the husband's sperm and the surrogate's egg.

''[When we met her] It was a feeling. You know when you can trust someone.''

Though the 37-year-old beauty requested her surrogate use her own medical team and had the baby in Los Angeles, she insists she didn't have too many demands for the woman.

She recalled: ''I straight-up told her, 'Look, I ate doughnuts every single day. If you want doughnuts and ice cream, go for it. Do whatever you feel. I'm not going to be picky like that. That's just ridiculous.' ''

While Kim ''hated'' being pregnant and would recommend surrogacy to others, she admitted she wished she had been able to carry her daughter herself.

She said: ''I hated being pregnant. But as much as I hated it, I still wished I could have done it on my own. The control is hard at the beginning. Once you let that go, it's the best experience. I would recommend surrogacy for anybody.''

During her previous deliveries, Kim suffered from placenta accreta and she admitted her mother, Kris Jenner - who was there for the birth of North - still gets emotional when the complication is discussed.

She explained: ''After giving birth, your placenta is supposed to come out. But mine was stuck. That's what women usually die from in childbirth - you haemorrhage and bleed to death and they can't stop it. To get it out - it's so disgusting - the doctor had to stick his whole arm in me and scrape it off. It was the most painful.

''To this day, if you mention it to [mom], she'll cry. It was traumatic.''