Khloe Kardashian Reveals How Kylie Jenner's Pregnancy Secret Was Almost Spoiled

Kylie Jenner at adidas event
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Kim Kardashian West, meanwhile, calls it 'the best-kept secret of our generation.'

Kylie Jenner did a pretty good job of hiding her pregnancy -- but one outing could have spilled her secret in the blink of an eye. 

In a new promo for Sunday's Keeping Up With the Kardashians, Kim and Khloe Kardashian discuss how hard Kylie tried to keep her pregnancy private and revealed the one instance that almost blew it. 

"The funnest game ever is the Kylie pregnancy game," Kim says in the clip, posted to E! "There were pictures of her out on TMZ and she looked so skinny."

"Yeah, because it's the angle. They got her face-on," Khloe replies. "But if they got a side shot, it would have been over for her!" 

"It would have been over!" Kim agrees. "Over!"

Later in the clip, Kim calls her little sister's pregnancy mystery "the best-kept secret of our generation" -- though Kylie insists she just wanted to keep the experience to herself. 

"Your friends deserve awards," Kim raves. "'Cause seriously, now you know you have some real ones 'cause that never would've happened in my day."

Watch below. 

Though ET learned through sources that Jenner was pregnant, she didn't confirm the news until days after she welcomed her daughter, Stormi, on Feb. 1. 

She's since been open with fans about her pregnancy journey and how she's coping with life as a new mom. See more on Jenner in the video below. 

Keeping Up With the Kardashians airs Sundays at 9 p.m. ET/PT on E!