The brunette heiress announced her pregnancy not long after her wedding in June, and she is now three months pregnant.
This is the first time we have seen a proper glimpse of her little bump!
Tamara, 29, was glowing on the night, held at London's Natural History Museum, and is clearly taking this pregnancy in her stride, as she wore a pair of killer heels.
New hubby Jay Rutland accompanied Tamara to the event.
Our party insider tells us: "Once inside, Tamara spent most of the night sat down and Jay was by her side the whole time. He looked very protective." So cute!
Tamara's little sister Petra gave birth to her first child, Lavinia, earlier this year and Tamara can't wait for her baby to meet his or her older cousin.
"I want them to be as close as me and my sister. And I would just love to have a little girl who would be super close to Lavinia," Tamara told MailOnline.
"There's only going to be a year between my baby and Lavinia so that would be amazing. Lavinia is the cutest little pooch in the world."
While some mums prefer to keep the sex of their baby a mystery until the birth, Tamara has no such plans.
She added: "I'm definitely going to find out the sex! I need to know, I need to plan. It's nice to have a surprise, but I couldn't cope with not knowing for the next six months!
"Having the scan was the most exciting, most amazing experience in the world. I'm not very emotional, but both Jay and I cried."
Aw. Congrats, you guys.
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