Photo: "You gave me the strength I didn't know I had" - Pregnant Serena Williams pens sweet message to her unborn child

Just days after revealing that she is 20 weeks pregnant, Tennis star Serena Williams posted another photo showing her growing bump along with  touching message to her unborn baby. The-mother-to-be captioned the photo: 

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