That bit of privacy went out the window when Kardashian's boyfriend, Kanye West, revealed during a Dec. 30 concert in Atlantic City, N.J., that they are expecting their first child together.
Now that the word is out, Kardashian says her motherly instincts have made her pull back from being so open about her personal life.
"I think that definitely kicks in where you're like, 'OK, I have to go in protect mode,' and as ironic as it sounds, you live your life on a reality show but then when you grow up ... certain things change your life that make you want to be more private and this is definitely one of them."
The couple went public with their relationship in March.
Kardashian married NBA player Kris Humphries in August 2011 and their divorce is not finalized.
West rarely grants interviews, and the 35-year-old rapper is the ying to the Kardashian family's "out there" yang. Kardashian says she is somewhat influenced by West's approach.
"When you spend time with someone, you learn things from them, so I see what (his) views are in wanting to be private, so that's a choice we make together as a family just in how we're gonna raise our kid," she said. "... But my personal experience of having really open relationships on the show, I've done that, and for me I feel like I got really scrutinized when people didn't maybe understand my decisions at some point, so I feel like after that experience I've become more private more so than just like Kanye's views or anything."
Kardashian is due in July.
A new season of her reality show with her sister Kourtney, "Kourtney and Kim Take Miami," premieres Sunday on E! (9 p.m. EST).