At six months pregnant, Serena Williams is refusing to let her baby bump get in the way of forehands or backhands - she is still working out and playing tennis to retain her touch, her long-time coach told Reuters on Saturday.

Although the 23-time Grand Slam champion has not played competitively since winning the Australian Open in January, she has been soaking up the Roland Garros atmosphere this week, watching sister Venus play and catching up with friends.

"She's working out and she even played tennis the other day," her long-time coach Patrick Mouratoglou said in an interview in Paris on Saturday.

"She said to me she didn't want to lose her touch. Of course she went slow, but she wanted to hit the ball."

The American former world No 1, who announced her engagement to Reddit co-founder Alexis Ohanian in December, posted a picture on Snapchat on April 20 with the words "20 weeks". That means Williams would currently be 26 weeks pregnant.

Although the three-time French Open winner deleted the 20-week photo afterwards, her pregnancy was confirmed later that day by her publicist, Kelly Bush Novak.

Speaking at a conference hosted by media organization TED a week later, Williams said she had been keeping a diary of her pregnancy and had accidentally posted the shot online.

Although she turns 36 in September, and achieved a long-time goal when she won an Open era-record 23rd major title in Australia, she has every intention of coming back, according to Mouratoglou.

"When she called me to tell me she was pregnant, in the same sentence she said: 'I'm pregnant but I will be back, will you wait for me?'" the Frenchman said. "She is really planning on coming back, and she said to me, 'I am not done, I cannot finish like this.'"

Reuters