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."
"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."
"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