Big congrats to Sienna Miller — the Brit queen just announced she’s pregnant at 43 with Baby Number 3 … and naturally, she did it in the chicest way ever!

Sienna — who’s expecting the child with actor Oli Green, their second together — hit the 2025 Fashion Awards red carpet in London Monday night, rocking a sheer, lingerie-inspired white Givenchy gown that perfectly showed off that bump.

The “American Sniper” star was posing away on the red carpet, looking angelic in her gown, which exposed not only her bump but also her white underwear.

She’s also been open about freezing her eggs at 40 due to the pressure of expanding her family … though it’s unclear if that played a role in her two recent pregnancies.