(CNN) Serena Williams is still wrapping her head around her own pregnancy.
"It just doesn't seem real ... 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," Williams told Vanity Fair in a cover story for its August issue.
The tennis champion appears on the cover in the nude, proudly showing off her baby bump. The photo was taken by Annie Leibovitz, who famously photographed a very pregnant Demi Moore in a similar pose back in 1991.
Williams, who is expecting her first child with fiancé and Reddit founder Alexis Ohanian, said that she has done little to prepare for a baby aside from converting a guest room into a nursery.
"I don't know what to do with a baby," Williams said. "I have nothing ... I've done absolutely nothing for the baby room."
The 35-year-old said that she was gearing up for the Australian Open in January when she took a pregnancy test that changed her life.
"[I] did a double take and my heart dropped," she said when seeing the positive pregnancy result. "Like literally it dropped." She took five more tests -- all positive.
"Oh my God, this can't be -- I've got to play a tournament," she said. "How am I going to play the Australian Open? I had planned on winning Wimbledon this year."
But for Williams it all worked out and she went on to win the Australian Open.
As for Ohanian, he couldn't be more excited about the future they have together.
"I find myself just wanting to be better by simply being around her because of the standard she holds," he said.