Serena is now the second tennis player to take a break from the sport in recent times after Victoria Azarenka chose to take one in June as she gave birth to her son Leo in December and is planning to return to the tennis court later this year.
Her representatives have confirmed to Press Association Sport that she will not feature in any more tournaments this year, but is planning a return in 2018.
As the New York Daily News points out, Williams was apparently a few weeks pregnant in January when she beat her sister Venus to win the Australian Open.
The legendary tennis player announced her engagement to Alexis Ohanian, the co-founder of Reddit, in December.
Williams hasn't played since winning the Australian Open in January - a little less than 12 weeks ago.
Tennis icon Serena Williams has a new title to add to her mantle: mum-to-be! The BBC's resident tennis boffin doesn't think we'll see her in smashing backhands until the French Open next year, which will take place four months before her 37th birthday. Serena reportedly does not have any plans to permanently put down her racket anytime soon, but her priorities will shift with this new bundle of joy.
The photo, captured by U.S. media, shows Williams in a yellow swimsuit with what appears to be a baby bump.
Williams will be the second top player in less than a year to take time away from the tour to have a baby.
Belgium's Kim Clijsters came out of retirement at the age of 26 after having a child and won three Grand Slam titles.
Former No 1 Victoria Azarenka of Belarus, 27, missed most of the 2016 season to have a baby and is expected to return to the tour this summer. Only one woman has won more: Margaret Smith Court, who claimed part of her 24 during the amateur era.
At the time she blamed the withdrawal, which meant she lost her number one world ranking to Angelique Kerber, on a knee injury.
"She's already done so much, does she need more?"
Neither Williams nor Ohanian have posted anything else on social media or commented publicly on Williams's potential, but her fans instantly chimed in, congratulating her on her latest achievement.
Sister Venus, 36, has won seven grand slam singles titles.
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