Thursday was no exception for the star, who hosted a dinner in aid of non-profit organisation Animal Haven in Manhattan accompanied by a very special person, her brother Conrad.
Nicky Hilton showed off her growing baby bump in a Caroline Herrera number
For the special event, the 32-year-old mum-to-be, who is married to British banking heir James Rothschild, wore a stunning figure-hugging green creation by Carolina Herrera.
She accessorised her look with a gold clutch and wore her blonde hair swept up into an elegant updo, keeping her make-up looking natural.
Nicky married James Rothschil in July last year
Paris Hilton's sister shared a snap of the night which showed her posing next to her brother. "Shout to my brother for being the best date tonight 👫," she captioned the shot.
The event, which was also attended by actor Jason Biggs, was aimed at raising money for Animal Haven, an organisation which helps home orphaned animals in New York. Guests were treated to a glamorous dinner and had the opportunity to meet with some of the orphaned pets that are up for adoption.
Nicky Hilton's pregnancy was confirmed in January, six months after their lavish London wedding. The couple were said to be "over the moon" at the happy news.
"Nicky is very excited to become a mom, she is feeling great!" a source told People at the time. "They've just begun telling close friends and family. Nicky and James are over the moon!"
The happy news capped off an incredible 12 months for Nicky and James, who Paris Hilton as her maid of honour.