She later shared a moving tribute to her unborn child on her Instagram page, saying how she “couldn’t wait to meet them”.
Serena, who has still been playing during her pregnancy, then gave a big clue that she will resume playing tennis once she’s had the child as she wrote: “I can’t wait for you to join the players box next year.”
Keen fans worked out she was pregnant when she won Grand Slam title number 23 at the Australian Open in January this year.
She will be on maternity leave for the rest of 2017, missing Wimbledon – but says she will be back as a mum on tour next year.
Although Serena previously said that the sex of the baby will be a “surprise”, it seems sister Venus may have outed the gender during an interview with Eurosport – where she referred to the tot as a “she”.