It's a Girl! Serena Williams and Alexis Ohanian Welcome Daughter Alexis Olympia

Serena Williams‘ cheering section just gained a new member.

The tennis champ has welcomed her first child — a daughter! — with her fiancé, Reddit co-founder Alexis Ohanian, multiple outlets report.

Baby girl arrived Friday, Sept. 1 at St. Mary’s Medical Center in West Palm Beach, Florida, weighing in at 6 lbs., 13 oz., according to a Tweet from WPBF-25 news producer Chris Shepherd.

The couple confirmed the news on Instagram Sept. 13, revealing their daughter’s name is Alexis Olympia Ohanian, Jr.

“Obviously I’m super excited. Words can’t describe,” sister Venus told ESPN moments before stepping on to the court for her U.S. Open match in Queens, New York Friday afternoon.

Beyoncé took to Instagram to send her well-wishes, posting a photo of Williams during her pregnancy with the words “Congratulations Serena!”

PEOPLE confirmed Williams’ pregnancy in April after the 35-year-old inadvertently revealed on Snapchat that she was 20 weeks along. Williams and Ohanian, 34, were engaged in December.

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Ahead of their daughter’s birth, the couple revealed that they were opting to leave the baby’s sex a surprise, though both shared that they felt they were having a girl.

“[Serena] won the Australian Open while pregnant. And she remarked that she feels like it has to be a girl because everything that that baby went through and handled like a champ, only a woman could be strong enough to take on,” Ohanian said during a late-night talk show appearance in early August.

The pro athlete echoed her fiancé’s sentiment to Vogue in its September issue, revealing, “I have a strong suspicion that it’s a girl.”

In the same interview, Williams also admitted that she was “nervous” about giving birth, lamenting, “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,” Williams added.

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She was also anxious about motherhood in general, sharing that she didn’t feel like “a baby person.”

“That’s something I have to work on,” Williams said. “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?’ “