The mother-to-be cradled her baby bump amid a beautifully lit background.
She exhibited some Parisian realness with her colorful blue top, yellow jacket and hat and multi-colored skirt.
"18 weeks bumping!" she wrote on the corresponding post.
Gretchen is currently expecting her first child with fiancé Slade Smiley. She made the exciting announcement on Monday, December 17.
It hasn't been an easy road for the couple on their journey to baby number one.
Gretchen revealed that she lost 14 embryos during her devastating IVF journey prior to revealing her pregnancy late last year.