Serena Williams will return to world number one next week but may not stay atop the rankings for long after hinting on Wednesday that she is pregnant.

The confirmation came hours after Williams, due to regain to the No. 1 world ranking next week, set off a day of frenzied speculation with a short-lived selfie posted on social media - posing for a photo in a yellow one-piece swimsuit on Snapchat with the caption: "20 weeks."

Williams deleted the photo shortly after it appeared and waited more than six hours to make any public comment, stoking debate among tennis fans about whether or not she was joking.

"I'm happy to confirm Serena is expecting a baby this fall," Los Angeles-based publicist Kelly Bush Novak said.

Bush Novak told Reuters that Williams intended to sit out the remainder of the 2017 season and return next year.

Williams, the world's highest paid female athlete, announced her engagement to Reddit co-founder Alexis Ohanian last December.

Days ago she seemed to quell speculation about impending motherhood with an Instagram post praising a newly published guidebook for new mothers by former Destiny's Child singer Kelly Rowland, adding in the caption: "One of these days I hope to apply this (but for now I'll stick to my dog Chip)."

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 singles title at the Australian Open in January.

Her victory over older sister Venus Williams broke a tie with Steffi Graf for the most Grand Slam singles championships in the sport's modern era. Serena Williams has not played since then, citing a knee injury.

Fans and celebrities reacted with a mixture of awe and glee to Williams' Snapchat post.

"Serena Williams was pregnant when she won her 23rd grand slam tournament at the Australian Open. And did not drop ONE SET. Let that sink in," wrote Twitter user @noelleharmony.