Pregnant Serena Williams shares heartfelt message to 'dearest baby' after return to No. 1 ranking

Serena Williams recently opened up about her pregnancy after climbing to the top slot on the Women's Tennis Association ranking Monday, sharing the celebratory moment in an emotional message to her baby-to-be.

The 35-year-old star athlete took to Instagram to share a photo of her current baby bump in a heartfelt message to her unborn child, marking the first time she's publicly shared anything about her pregnancy following her Snapchat announcement the previous week.

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"My Dearest Baby, you gave me the strength I didn't know I had. You taught me the true meaning of serenity and peace," Williams wrote. "I can't wait to meet you. I can't wait for you to join the players box next year. But most importantly, I am so happy to share being number one in the world with you.... once again today. On @alexisohanian bday."

Williams concluded, "From the world's oldest number one to the world's youngest number one. -Your Mommy."

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Following her post, Annie Apple, mother of rookie Giants' corner Eli Apple, was inspired to also tweet a warm letter to her son.