According to sources, Kim, 34, and 38-year-old Kanye used male-only embryos during IVF treatment to ensure she do conceived a boy.
An insider told Us Weekly: "Kanye loves Nori [their two-year-old daughter] more than anything.
"But to make his world complete, he wanted a little boy, an heir."
Kim's struggle to conceive a second time was heavily documented, with her even fearing at one point she wouldn't be able to carry her own child.
The Keeping Up With The Kardashians star, who is thought to be due in December, has already had to shut down a couple of rumours about her baby.
Earlier this month it was claimed she and Kanye were expecting a boy - before they made the official announcement.
Kim rubbished the allegations, insisting she and Kanye hadn't to anybody the sex at that point.
Then stories emerged reporting that the superstar couple were planning to call their second child South.
She was quick to dismiss this, insisting the name was 'stupid'.