Serena Williams
Serena Williams took six pregnancy tests to confirm she was expecting her first child in January 2017Theo Wargo/Getty Images

Serena Williams is seen like never before on the cover of Vanity Fair magazine, posing naked and baring her baby bump in a candid photo shoot.

Gracing the front of the US publication's August edition, Williams, 35, poses for a side profile which displays her protruding baby bump. Inside the issue, the tennis champion is joined by her fiance Alexis Ohanian, who lovingly embraces Williams in a series of intimate images shot by famed photographer Annie Leibovitz.

In the accompanying interview, Williams details her surprised reaction to learning she was pregnant with her first child in January 2017. After feeling physically unwell at the start of the Australian Open, Williams was encouraged by a friend to take a pregnancy test.

The sports star recalls: "I'll take it just because (a) to prove you wrong and (b) because it's fun, whatever. It's like a joke. Why not?

"I did a double take and my heart dropped. Like literally it dropped. [I thought] '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 asked Ohanian, 34, to fly out from San Francisco to Melbourne and delivered the exciting news by handing the Reddit co-founder a paper bag with the six positive pregnancy tests she took. Ohanian has taken great efforts to prepare for the baby's arrival, including the introduction of a tip jar to prevent him from swearing.

The tech entrepreneur met Williams by chance in Rome in 2015 and he proposed in December 2016 at the Italian restaurant where they first met. Ohanian gushed about his wife-to-be: "I felt like a door had been opened to a person who made me want to be my best self... I find myself just wanting to be better by simply being around her because of the standard she holds."

The Grand Slam champion added: "I knew it was coming. I was like, 'Serena, you're 35, you're ready. This is what you want."

Williams is currently six months pregnant and admits she is still coming to terms with the looming chapter of parenthood. She explained: "It just doesn't seem real. I don't know why. Am I having a baby? I don't know what to do with a baby. I have nothing ... I've done absolutely nothing for the baby room. I'm trying to enjoy the little freedom I have left.

"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."