Serena Williams, the most successful female player of the Open era, is pregnant – just 12 weeks after winning her record 23rd Grand Slam.
The American, 35, is due to give birth in the autumn, says her representative.
The world number two posted a picture on social media app Snapchat, posing in a mirror with the message: "20 weeks", before deleting it.
Williams will miss the rest of the season, having not played since winning in Melbourne, citing a knee injury.
Williams, who will return to world number one next week, would be eligible to retain her ranking under the WTA special ranking rule if she is ready to play her first tournament within 12 months of giving birth.
Former world number one Victoria Azarenka gave birth to her first child in December and is expected to return to competition at the end of July.
Belgium's Kim Clijsters, meanwhile, won the US Open in 2009 just 18 months after giving birth to her daughter.