Khloe Kardashian is unsure if she wants her ex-partner Tristan Thompson to be her sperm donor.

The 'Keeping Up With The Kardashians' star - who already has True, two, with her ex-boyfriend - is keen to have more children but doesn't know whether she should ask the basketball star to be her donor or go another way.

Speaking in a sneak peek of the family's E! reality show, she said: ''I've been doing hormone injections for about five days and the injection process has been fine. I don't know why, I'm like, 'Oh, okay, it's not that bad.' Dr. Huang was saying the bonus of doing embryos you get to see what are your stronger embryos, which are healthy, you get to already know all that by mixing them with sperm. Which I do have a sperm donor.''

And Khloe went on to admit she worried about what would happen in the future if she met someone else and changed her mind about the whole thing, and instead wanted to have a baby with her new partner rather than go for Tristan.

Speaking about the possibility, she added: ''He has to sign legal paperwork that he would just be my sperm donor. But you never know - like if what in three years I get married to someone and I'm like, 'You know what? I don't want that.'

''After my doctor's appointment, I talked to Tristan, because if you can create embryos and do all the DNA testing, I do think that's the smarter choice. But it's weird, because Tristan and I, we're not together. I don't know which way to go.''