Aug. 1 (UPI) -- Serena Williams used her platform this week to encourage black women to "speak out for equal pay."
The pregnant 35-year-old tennis star discussed Monday on Black Women's Equal Pay Day how the gender pay gap impacts women of color the hardest.
"July 31 is Black Women's Equal Pay Day, which represents the number of days into 2017 a black woman must work to earn the same pay a white man made in 2016 -- that's nearly 8 extra months!" she explained on Instagram.
Williams further explained in a lengthy essay for Fortune that black women are "37 cents behind men in the pay gap," or that "for every dollar a man makes, black women make 63 cents." The disparity means the average woman of color has to work eight months longer to earn the same amount their male counterpart does in a year.
"Unfair pay has prevailed for far too long with no consequence," Williams wrote. "Changing the status quo will take dedicated action, legislation, employer recognition, and courage for employees to demand more. In short, it's going to take all of us. Men, women, of all colors, races and creeds to realize this is an injustice. And an injustice to one is an injustice to all."
"Every step forward you take is two steps of progress for womankind," she told women of color. "Let today serve as a reminder that we have a voice. We deserve equal pay for our mothers, our wives, our daughters, our nieces, friends, and colleagues -- but mostly, for ourselves."
"Black women: Be fearless. Speak out for equal pay," the star urged. "Every time you do, you're making it a little easier for a woman behind you. Most of all, know that you're worth it. It can take a long time to realize that. It took me a long time to realize it. But we are all worth it."
Williams is expecting her first child with her fiancé, Reddit co-founder Alexis Ohanian. She denied she and Ohanian married at a secret wedding while discussing her pregnancy in an interview with E! News in July.