The Calvin Klein model displayed her bump in a form-fitting bright coral dress which featured a simple tank style and straight full-length skirt.
Stone kept the rest of the look suitably unfussy, wearing her long blonde hair loose around her shoulders and going for a classic smokey eye.
Walliams announced the couple's baby news on Twitter, writing: "'Some wonderful news. My beautiful wife Lara is pregnant. We are having a baby! It is due next year and we both couldn't be happier. Dx"
Also in attendance at the film awards were couple John Krasinski and Emily Blunt. Blunt chose a pale Calvin Klein strapless dress with cut-out detailing for the occasion.
Actess Amy Adams looked chic in a Giorgio Armani black peplum cocktail dress and a pair of cute Mary Jane heels.