Serena Williams Announces She's Expecting Baby No. 2 at Met Gala

The couple, who share four-year-old Alexis Olympia, made a stunning arrival to the annual costume gala but it was an Instagram post from the tennis great that had everyone talking.

Serena captioned a photo from the night, "Was so excited when Anna Wintour invited the 3 of us to the Met Gala" -- of course her Gucci wrapped baby bump was unmistakable too.

Last August, Serena wrote in an essay for Vogue that she would be stepping away from tennis to focus on growing her family.

"In the last year, Alexis and I have been trying to have another child," Serena wrote. "And we recently got some information from my doctor that put my mind at ease and made me feel that whenever we're ready, we can add to our family. I definitely don't want to be pregnant again as an athlete. I need to be two feet into tennis or two feet out."

The theme for this year's Costume Institute exhibition is "Karl Lagerfeld: A Line of Beauty," dedicated to the late fashion designer. The dress code is both a simple prompt and a challenge to realize, asking guests to come dressed "in honor of Karl." Lagerfeld headed his own eponymous brand as well as designed for Patou, Balmain, Chloé, Fendi, and Chanel.

Penélope Cruz, Michaela Coel, Roger Federer, Dua Lipa, and of course Vogue's Anna Wintour are co-chairs for the star-studded gala this year.

Meanwhile, fans can experience the exhibit at The Metropolitan Museum of Art in New York City from May 5 to July 16.