In something of a bait and switch ... Pete Davidson 's girlfriend shared a busty thirst trap that she turned into a baby bump preview.

Model Elsie Hewitt posted the short vid to the Gram Thursday morning ... sporting a black bandana and adjusting a bikini top -- that appeared to be holding on for dear life -- before she backed away from the camera and cradled her tummy. She captioned the post ... "my little 🤰🏻" Getty

TMZ broke the story ... the 'SNL' star and EH were expecting back in July ... and they commented on the exciting news shortly after ... Elsie posted snaps of them all loved up with the caption ... "Welp now everyone knows we had sex." Play video content

As we reported, Pete and Elsie were first linked in March and took their relationship to the n

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