Just a week after she announced she was 20 weeks pregnant with her first child, Serena Williams has given the world another glimpse of her growing baby bump.

The 35-year-old – who is engaged to Reddit co-founder Alexis Ohanian – shared the image on Instagram, penning an emotional tribute to her unborn baby.

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 @alexisohanian bday. ???? from the world’s oldest number one to the world’s youngest number one. -Your Mommy

A post shared by Serena Williams (@serenawilliams) on Apr 24, 2017 at 6:06am PDT

“My Dearest Baby, You gave me the strength I didn’t know I had,” she captioned the image.

“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.

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“From the world’s oldest number one to the world’s youngest number one. – Your Mommy”

The image comes as the 23-time Grand Slam winner – who was two months pregnant when she won the Australian Open earlier in 2017 – reclaimed the number one ranking on the WTA Tour for the eighth time in her career.

Williams also posted the snap to celebrate her fiancé's birthday.

It's the first time Serena has publicly referenced her pregnancy since she posted - and quickly deleted - her baby bump snap last week.

After her loving open letter, fiancé Alexis has also posted on social media, confirming the news.

A new Snoo is on the way! My number one, @serenawilliams, is pregnant (she announced officially earlier today) and I'm so excited to meet the little one. You keep amazing me. April 24 is a hard day for all of us Armenians; may we always remember the sacrifices our predecessors made; honor them through our successes; and appreciate our blessings.

A post shared by Alexis Ohanian ???? (@alexisohanian) on Apr 24, 2017 at 8:30am PDT

"A new Snoo is on the way!" he wrote on Instagram.

"My number one, @serenawilliams, is pregnant (she announced officially earlier today) and I'm so excited to meet the little one. You keep amazing me."

We can't wait to meet the new baby tennis champ either!