The popular 'supermum' jokingly rejected the suggestion she was pregnant again during a post-match interview.
The Belgian star dominated Spaniard Carla Suarez Navarro, taking just 62 minutes to win 6-1 6-3.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
She then stunned on-court interviewer Todd Woodbridge by repeating to the crowd a text message she said he had sent to Australian doubles player Rennae Stubbs.
"What did I say," Woodbridge asked.
"You said I looked pregnant," Clijsters replied.
"I'll tell you what it said. You said `She looks really grumpy and her boobs look bigger.'"
Woodbridge, stunned, laughingly declared his television career at an end before ushering Clijsters off court.
The Belgian shocked the world when she returned to the tour in 2009 after more than two years off following the birth of her child to immediately win the US Open.
She captured the title again last year, her third US crown and third grand slam and enters the Australian Open determined to climb back to the top.
"I'm working hard and trying to come close to where I was here a few years ago in the semi-finals and the final," Clijsters said.
She described Suarez Navarro as a "tricky" player but also said she found the balls bounced differently to her last match, forcing her to adjust her footwork.
"She's a tough player - I've practised with her before but I was happy with the way I played.
"I tried to dictate the points and it worked," she said.
