Getting pregnant used to be one of Serena Williams' biggest fears, but she surprised herself when the time came.

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"Once I found out, something happened that surprised me. I became really calm," she told Vogue of finding out she was pregnant while training for the Australian Open. "I thought, 'You have to win, but you're allowed to lose, because you have something to look forward to.'"

Now, the tennis star has childbirth and motherhood to conquer next.

"I'm nervous about childbirth," she told Vogue. "I'm not a spring chicken. The one thing I really want is an epidural, which I know a lot of people are against, but I've had surgeries galore, and I don't need to experience any more pain if I can avoid it. But the biggest thing is that I don't really think I'm a baby person. Not yet. That's something I have to work on. I'm so used to me-me-me, taking care of my health, my body, my career. I always ask, 'Am I going to be good enough?'"

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While Williams may be second-guessing herself, she has a close-knit group of friends who are always there to support her. One, actress and girlfriend to Prince Harry, Meghan Markle, thinks her friend will be the “best” mom.

“She will be an amazing mom -- the very best, because she is so attuned to balancing strength and sensitivity,” Markle said, according to Vogue. “Plus, given that she is pretty epic at karaoke, I think she’ll put her signature Serena spin on singing lullabies for the baby. I can’t wait for that!”

Williams announced that she was expecting her first child with fiance Alexis Ohanian in April after the couple got engaged in December. She's due next month and has decided to wait until the baby's birth to find out the sex of the child, but Williams and Ohanian feel confident it's a girl.

"I was playing in 100-degree weather, and that baby never gave me any trouble," Williams said of competing in the Australian Open while pregnant. "Ride or die. Women are tough that way."

Read more at Vogue.

Tennis superstar Serena Williams with Daniel Ricciardo of Australia and Red Bull Racing and Max Verstappen of Netherlands and Red Bull Racing during the Monaco Formula One Grand Prix at Circuit de Monaco on May 28, 2017 in Monte-Carlo, Monaco.  (Photo by Mark Thompson/Getty Images)

Credit: Mark Thompson

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Credit: Mark Thompson