Socialite Nicky Hilton debuted her Baby Bump at the amfAR Gala in New York City on Wednesday (February 10).

Joined by big Sister Paris Hilton, the mom-to-be, 32, wowed in a white lace dress with a sheer cut out around her growing belly.

“I am so excited. I can’t wait to be an Aunt — my sister is thrilled,” Paris, 34, told PEOPLE at the posh event.

And while Paris will “for sure” be the cool aunt, she’s not sure about the baby’s gender.

“She’s so tiny right now you can’t even tell [she’s pregnant],” Paris said. “Usually you can tell with the size if it’s maybe a boy or girl, but we have no idea — and they want it to be a surprise.”

Earlier this month, Nicky stepped out in NYC in a casual ensemble that hid her barely there Bump.

This will be the first child for Nicky and husband James Rothschild.

The couple were wed at Kensington Palace in London in July 2015.

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