In the emotional post to Reddit, the website her fiance Alexis Ohanian co-founded, Serena reveals she was "called a man" growing up, and that she worries about how she would handle it if her daughter gets teased in the same way.
The 35-year-old thanked her mum for her unwavering support and for giving her the courage to show the world "what some women look like."
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"I was looking at my daughter (OMG, yes, I have a daughter 😳) and she has my arms and legs! My exact same strong, muscular, powerful, sensational arms and body," the letter started.
"I don't know how I would react if she has to go through what I've gone through since I was a 15 year old and even to this day."
"I've been called man because I appeared outwardly strong," Serena revealed. "It has been said that that I use drugs," she continued. "It has been said I don't belong in Women's sports - that I belong in Men's - because I look stronger than many other women do."
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"Thank you for being the role model I needed to endure all the hardships that I now regard as a challenges - ones that I enjoy," she wrote. "I hope to teach my baby Alexis Olympia the same, and have the same fortitude you have had."
This article originally appeared on marie claire