It may have been son Rob Kardashian's birthday yesterday, but Kris Jenner was the one in her birthday suit!

For Rob's 25th birthday, the "Keeping Up with the Kardashians" matriarch shared a topless pregnant photo of herself from back when she was carrying her only son.

"Happy 25th birthday to my wonderful, handsome son, Rob!!," she wrote on her Celebuzz blog yesterday. "Rob, you are the best son a mother could ask for and you make me proud every day. I love you so much!!"

Check out more stars who have posed nude while pregnant in the gallery above.

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