Serena Williams appears to announce pregnancy

Serena Williams appeared to announce on Snapchat that she is pregnant.

Williams, who hasn't played in a tournament since winning her record-setting 23rd Grand Slam title at the Australian Open in January, posted this photo Wednesday with the caption "20 weeks."

The world No. 2, who cited a knee injury when she pulled out of recent tournaments in Indian Wells and Miami, announced her engagement to Reddit co-founder Alexis Ohanian in December.

If she is indeed 20 weeks along, that would mean Williams was already in the early stages of pregnancy when she beat sister Venus in Melbourne to break Steffi Graf's major-title record.

Williams would be the second former World No. 1 to become a mother in the past year. Victoria Azarenka announced her pregnancy last July and gave birth in December. She plans to return to the tour this summer.

Azarenka, though, is just 27. Williams will turn 36 in September, and it's unclear what the pregnancy would mean for her tennis career.