Serena Williams‘ daughter Alexis Olympia is turning 1 on Saturday, September 1st, but the day will be free of fanfare, according to her mom. At a press conference surrounding the U.S. Open, the 36-year-old tennis superstar explained why she and husband Alexis Ohanian aren’t planning a party for their daughter. “Olympia doesn’t celebrate birthdays,” said Williams. “We’re Jehovah’s Witnesses, so we don’t do that.”

According to Wikipedia, Jehovah’s Witnesses “is a millenarian restorationist Christian denomination with nontrinitarian beliefs distinct from mainstream Christianity,” and those who subscribe to the faith typically don’t celebrate birthdays, Christmas, Easter, and other holidays.

In the same interview, the athlete also explained that her daughter is “not very good in the car” and therefore she and her husband don’t tend to take her on long drives. “That’s one of the toughest things we work on,” Williams said. “She’s not good if we’re [going on] more than a five-minute ride.”

Williams sat down with Today’s Stephanie Ruhle recently, and revealed that she’s taken comfort in feedback she has received from other moms on social media. “When I missed Olympia’s walking, I posted about it and so many parents wrote in and said, ‘Don’t worry about it, I missed it too,’ ” she said in an interview that aired on the NBC morning show Wednesday, August 22nd. “I didn’t realize that it’s almost more normal to miss it than it is to make it,” she added. “So I really kind of rely on everyone’s help out there. It’s been so, so amazing.”