Although she turns 44 on Tuesday, September 26, WTA great Serena Williams will not be celebrating her birthday as her family does not believe in that tradition.

The 23-time Grand Slam champion, along with sister Venus Williams, was raised as a Jehovah's Witness, a subsect of Christianity. An important aspect of that belief is that those who practice the religion do not celebrate birthdays.

Both Serena and Venus followed their mother, Oracene Price at home in Saginaw, Michigan in converting to the religion in the early 1980's. On multiple occasions, Williams has spoken about her religious beliefs.

"Being a Jehovah’s Witness is important to me, but I’ve never really practiced it and have been wanting to get into it," said the former World No.1 in 2017.

Following her marriage and birth of 1st child Olympia, Williams re-affirmed her decision to not celebrate her daughter's first birthday in 2018. "We're Jehovah's Witnesses, so we don't do that," she said at a press conference.

Furthermore, she stated her husband Alexis Ohanian is very supportive of her decision. "Alexis didn't grow up going to any church, but he's really receptive and even takes the lead," she added. "He puts my needs first." But in raising Olympia, it has been a source of strength.

But why do Jehovah's Witnesses not celebrate birthdays you may ask? They base this choice on a mix of biblical interpretations, religious principles and their broader worldview.

Mentioned in the bible twice in Genesis and Matthew, witnesses note that in both cases, birthdays are linked with violence and negative outcomes, not joy or divine approval. They emphasize that the Bible gives instructions to commemorate some events (for example, Jesus’ death at the Lord’s Supper), but never commands birthday celebrations. Also it is more important to celebrate spiritual milestones (such as baptism or anniversaries of ministry) rather than personal ones.