As speculations were rife that Serena's post was about pregnancy, the 35-year-old soon deleted the post triggering a debate among tennis fans about whether or not she was joking.
Serena Williams shocked fans on Wednesday when she posted a shot on Snapchat indicating she is pregnant.
Williams and Alexis Ohanian, an American businessman and a co-founder of Reddit, announced their engagement in late December.
If Williams is indeed 20 weeks into her term, that would mean she was approximately two months pregnant when she captured her record 23rd Grand Slam tournament title at the Australian Open in January.
The win meant she surpassed German Steffi Graf's 22 Grand Slam titles in the Open-era. She was wearing a one-piece bathing suit with a caption reading "20 weeks". She did not drop one set. "Let that sink in", wrote Twitter user @noelleharmony on the social media site.
Williams was last spotted, in February, hanging around the tennis courts at Dolores Park in February, and it's fairly probable that she and Ohanion have been shacking up in the neighborhood - the Dolores Terrace/Liberty Hill area is a known preference of tech billionaires. She'll return to No. 1 on Monday, and despite the odds being stacked against her, a 24th Grand Slam doesn't need to be counted out just yet.
Clijsters is the most recent mother to gain Grand Slam glory after having a child.
She's not the oldest grand slam champion ever, though, with Ken Rosewall winning the men's title in Australia in 1972 at age 37. "Really, really nice to see", she added. Still, at the time, she was much more focused on the Australian Open.
Her sponsorship deals rake in about $20 million and business analysts say her impending motherhood would likely enhance her popularity among corporate sponsors.
Williams would appear to be out for the rest of this tennis season, a blow to a sport in which she is an unqualified star - and, of course, something that makes major titles easier to come by for other competitors.
Williams, who has played professionally for two decades, first gained the No. 1 ranking in 2002 and has held that spot for more than six years in total.