In it, the all-time Grand Slam champion poses for a selfie in a revealing yellow bikini with the suggestive caption: "20 weeks".
The star and her fiancé, Reddit co-founder Alexis Ohanian, 33, have kept their relationship mostly out of the spotlight before getting engaged in December of previous year.
Five-times Grand Slam victor Maria Sharapova, who returns to competition next week after a 15-month doping ban, could also benefit if she rediscovers her top form. She has not played since beating her sister Venus in the Australian Open final. A representative for Williams declined to comment on whether the post was a confirmation that she is pregnant. She was busy growing a new human inside her, and perhaps not quite ready to share the news with the world.
Serena Williams appeared to drop a major hint that she is pregnant on Wednesday.
The world renowned athlete has clearly taken some lessons in keeping secrets from her BFF Beyonce.More news: Maduro orders Venezuela army into streets
Tennis great Serena Williams has been a busy woman these past few months. She pulled out of Indian Wells and Miami last month, claiming that she had a knee injury. But the story spread quickly across the internet and soon the congratulations were flooding in from all quarters, both for Williams and for her fiancé Alexis Ohanian, the online entrepreneur who founded the Reddit network.
The 35-year-old star has previously dated the likes of Drake and Grigor Dimitrov, and recently admitted that she wants children.
Existing clients could tap into new markets with a pregnant superstar athlete, industry experts said. I always thought about leaving a legacy of fulfillment, living out your dreams, and giving back.
The win meant she surpassed German Steffi Graf's 22 Grand Slam titles in the Open-era.