Kim Kardashian West is ''absolutely petrified'' about the contents of a new biography of her.

The 'Keeping Up with the Kardashians' star - who is pregnant with her and husband Kanye West's second child - has reportedly warned family and friends not to speak to author Sean Smith as there are certain personal details, including information around her failed marriages to Damon Thomas and Kris Humphries, which she doesn't want to be made public.

A source told heat magazine: ''Kim is absolutely petrified. She's calling people she hasn't spoken to in years, asking them not to talk about her.

''Her biggest fear is two ex-boyfriends - including two rival rappers - being named in the book.''

Despite her efforts, author Sean has vowed 'Kim' will be a fascinating read, especially as so much of her life has been lived out in private.

He said: ''By modern standards Kim found fame quite late.

''She will be 35 when the book comes out, and for the great majority of her life, nobody had a clue who she was.

''Justin Bieber, for instance, is 21 and Miley Cyrus is 22. By their age, Kim had eloped to Vegas to get married and gone through her first divorce.

''It's like an x-rated version of 'Dynasty' with amazing dresses, bigger hair and much better make-up.''