Kim and Khloe Kardashian race to have a baby

Kim Kardashian is feeling the pressure to get pregnant now that her sister, Kim, is married.

26-year-old Khloe has been incredibly open about her fertility struggles, both with the media and on her reality show, Khloe and Lamar, claiming that she wants to have kids but is not "desperate to have a baby" with husband Lamar Odom.

But since sister Kim Kardashian married Kris Humphries last month, Khloe is worried that the new couple will beat her and Lamar in the race to have a baby.

A Keeping Up With the Kardashians show insider has told Us Weekly : "If Kim were to get pregnant first, that would cause tension, because it would highlight Khloe's struggle.

"There is some friction now because Khloe knows [Kim's pregnancy] is the next step and she feels terrible she can't get pregnant herself.

"The competition has really got her depressed."

And despite claims that the Kardashians play things up on their reality shows, a friend of Khloe's says her struggle is very, very real.

"Khloe is having major problems getting pregnant," the friend told Us Weekly, "It's not contrived for their reality show."

On her reality show earlier this year, Khloe admitted to 'freaking out' about her fertility issues.

"I'm sorry for…being on edge lately," she told her hubby, in an apology for snapping at him, " but I've been holding a lot of stuff in and trying not to bother you, but I've been freaking out about why I'm not pregnant.

"It's scary [thinking], 'Oh God, what if I physically can't have kids.'"