The retired tennis star announced the news on Instagram along with a photo of her and her husband Alexis Ohanian. It was captioned:
Was so excited when Anna Wintour invited the 3 of us to the Met Gala
They confirmed the speculations that she was referring to her pregnancy while on the red carpet.
Williams and her husband already have a daughter together. Back in 2017, she famously won her 23rd Grand Slam title at the Australian Open while she was pregnant with Olympia, who is now 5 years old.
She retired from professional tennis last year, just after the 2022 US Open, stating that she was focusing on family and other interests.
But since retiring, she has made it clear that she has not closed the doors on the possibility of a comeback.
At this years Met Gala, hosted by Vogue, Williams wore a black and white dress with pearls, a reference to the theme this year Karl Lagerfeld: A Line of Beauty.
She displayed a prominent baby bump during her and Alexis red carpet appearance.
There has been no confirmation as to how far along she is in her pregnancy.