Serena Williams says she is already looking forward to her on-court comeback - and she hopes her baby will be in the stands and watching her play.

Serena Williams says she is already looking forward to her on-court comeback - and she hopes her baby will be in the stands and watching her play.

The Australian Open champion, 35, told TED talk in Vancouver: "This (motherhood) is just a new part of my life. My baby's going to be in the stands and hopefully cheering for me."

She also paid tribute to her sister Venus, whose career is thriving at the age of 36.

"If she's still playing, I know I can play," she said.

Williams also revealed that her pregnancy announcement - via a picture on Snapchat - was accidental.

"I have this thing where I've been checking my status and taking pictures every week to see how far along I'm getting," she said.

"I was just saving them (for myself). I've been so good about it, but this was the one time it slipped."

She added that she knew she was pregnant while competing in Melbourne - a tournament in which she did not lose a single set.

"It wasn't very easy. You hear all these stories about people when they're pregnant - they get sick, they get really tired, really stressed out," she said.

"I had to really take all that energy and put it in a paper bag, so to say, and throw it away. Pregnant or not, no one knew and I was supposed to win that tournament. Every time I play, I'm expected to win. If I don't win, it's actually much bigger news."