In what promises to be Watch Mom's Guide to Sex 12 Onlinean excellent year in celebrity pregnancies, Serena Williams announced last week that she's expecting.

On Monday, she opened up on Instagram with a photo of her pregnant belly and a sweet note to her future child.

SEE ALSO: Serena Williams engaged to Reddit co-founder Alexis Ohanian
View this post on Instagram

"You gave me the strength I didn't know I had," Williams writes in the photo caption. "You taught me the true meaning of serenity and peace. I can't wait for you to join the players box next year."

Mashable Trend Report Decode what’s viral, what’s next, and what it all means. Sign up for Mashable’s weekly Trend Report newsletter. By clicking Sign Me Up, you confirm you are 16+ and agree to our Terms of Use and Privacy Policy. Thanks for signing up!

Williams also gave a brief shoutout to her fiancé Alexis Ohanian who posted an announcement of his own on Reddit, the website he co-founded.

A new Snoo is on the way! * u/kn0thing

Congrats, you two. Can't wait to see this kid's backhand.

Featured Video For You
Artificially intelligent robot can teach humans ping pong