The 70-year-old reacted to the American's announcement last week that she is pregnant with highly derogatory remarks.
At a press conference ahead of Romania’s Fed Cup play-off against Great Britain, which the home team went on to win, Nastase reportedly said of Williams’ pregnancy: "Let's see what colour it has. Chocolate with milk?"
He went on to verbally abuse Britain's players - reducing Jo Konta to tears - and captain Anne Keothavong, before he was escorted from the venue and banned from all ITF events pending an investigation.
And now Williams, who returned to world No 1 this week but will sit out the remainder of the season, has hit back.
In a statement released on Instagram, she says: "It disappoints me to know we live in a society where people like Ilie Nastase can make such racist comments towards myself and unborn child, and sexist comments against my peers.
"I have said it once and I'll say it again, this world has come so far but yet we have so much further to go....
I am not afraid unlike you. You see, I am no coward.
She then goes on to quote a poem by Maya Angelou, adding: "Does my sassiness upset you? Why are you beset with gloom? You may shoot me with your words... you may try to kill me with your hatefulness, but still like air I rise."
Williams then backs the ITF in their investigation by saying: "I humbly thank the ITF for any consideration given to all the facts in this case. They will have my full support."
Read the original article on Eurosport: Serena slams 'racist comments towards myself and unborn child’ by Nastase