She's getting all the feels!

Serena Williams announced she was five months pregnant with her first child last week, and her pregnancy hormones must be kicking into overdrive, because she penned a touching letter to her unborn child on Instagram this morning.

"My Dearest Baby, you gave me the strength I didn’t know I had. You taught me the true meaning of serenity and peace. I can't wait to meet you. I can't wait for you to join the players box next year," she wrote on a photo of herself cradling her bump on the beach.

"But most importantly, I am so happy to share being number one in the world with you.... once again today. On @alexisohanian bday. 😉 from the world's oldest number one to the world's youngest number one. -Your Mommy," she added.

It sounds like she's ready to ace motherhood!