NEW YORK - Serena Williams unveiled her pregnant body in a nude Vanity Fair cover photo on Tuesday and detailed the story of her romance with fiance Alexis Ohanian in an article for the magazine.

The American 23-time Grand Slam singles champion proudly displays her pregnant stomach, with a small waist chain the only item she wears in the image by famed photographer Annie Leibovitz.

Williams said in the story she learned she was pregnant just before the Australian Open, which the 35-year-old American won to set the Open-era record for Grand Slam singles titles and move one shy of Margaret Court's all-time mark.

Williams revealed in April she was pregnant and would not play again this year. In the story, she insisted she will return to tennis in January, which would allow her to defend her Australian Open crown.

"I don't think my story is over yet," she told the magazine.

Williams and Ohanian, the 34-year-old co-founder of social-media website Reddit, will be married this year after their child is born, according to the article.

They announced their engagement last December after meeting in 2015 in Rome.

In telling how Williams discovered she was pregnant, the article said she had thrown up and her breasts had enlarged after a poor showing in her first match of the season in Australia.

She said she took a pregnancy test after a friend had nagged her to, dismissing the idea at the time as a joke as she was preparing for a sponsor appearance.

"I went back to finishing hair and makeup, was laughing. I was getting the styling done. An hour and a half later, I went back to the bathroom and I totally forgot about it because it was impossible for me," Williams recalled.

"So I went back to get dressed and I went back in the bathroom and I was like, 'Oh yeah, that test.'"

Williams said she "did a double take and my heart dropped. Like, literally it dropped."

"Oh my God. This can't be. I've got to play a tournament. How am I going to play the Australian Open? I had planned on winning Wimbledon this year."

Williams sent her friend to the store to buy five more pregnancy tests, each producing the same result.

She telephoned Ohanian to fly to Melbourne early and when he did, she handed him a bag with the six positive tests, shocking him as well, according to the story.

Williams was examined by a doctor who assured her she could play the Australian Open without harm to the fetus. She didn't drop a set in capturing the title.

"It just doesn't seem real. I don't know why. Am I having a baby?" Williams told the American magazine last month.

"If you would have told me last year in October or November that I would have a baby, not be pregnant but have a baby, I would have thought you were the biggest liar in the world.

"This is kind of how I am right now. This is happening sooner than later and it's going by so fast."

She plans on preparations for the baby in the next few weeks, when moving will be more difficult and she will be "bored to tears".

"I don't know what to do with a baby," she said. "I have nothing ... I've done absolutely nothing for the baby room."

Agence France-Presse