Researchers who study pregnancy in high-performing athletes said her training during pregnancy, the speed of her body's recovery after giving birth and her will power are the keys to Williams returning to top-level play.
The 35-year-old posted a picture of herself in a yellow swimsuit with a prominent bump - she captioned the image "20 weeks".
Williams, 35, has not played a match since winning her 23rd Grand Slam singles title at the Australian Open on January 28, when she would have been close to two months pregnant, if the caption on her deleted photo was accurate. She later took the photo down, but sources close to Williams told TMZ she is pregnant, although her reps have not yet confirmed the pregnancy.
With 23 Grand Slam wins, Williams holds the record for the most by a player in the Open Era.
The younger Williams sister is just one Grand Slam short of Margaret Court, who collected many of hers in an era when the difficulties of worldwide travel often diluted the fields. No leading singles player has returned from pregnancy at Williams' age.
A spokeswoman, Amy Binder, said the tour had not received any confirmation from Williams.
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.
I'm proud to have opened [two] schools in Africa and one in Jamaica [through the Serena Williams Fund and its partners].
She has bestrode tennis like a colossus and now it looks like she may have won the Australian Open, while in the early stages of pregnancy. Another former No. 1 and major champion, Victoria Azarenka, has announced she'll be getting back on tour soon after having a baby. In addition to Clijsters, Evonne Goolagong and Margaret Court also won Grand Slams after becoming mothers. As if her career wasn't already filled with the wildest accomplishments.
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. Another former world number 1 and major champion, Victoria Azarenka is also angling for a return to the game, after becoming a mother a year ago.
Sister Venus, 36, has won seven grand slam singles titles.