Following the baby news, Beyonce was the first to congratulate Williams on social media.
After accidentally announcing her pregnancy via Snapchat in April, Williams has been very open in documenting her journey to motherhood online -- although she kept one big secret. She opted to keep the sex of the baby a surprise until birth, saying on Instagram that there are "so few surprises in life these days."
In an exclusive interview with ET in July, Williams said that she just started putting together the baby's nursery. "I've been working on it a little bit, but it's a little difficult when I'm trying to go for neutral colors," she said.
Williams won the Australian Open in January -- without dropping a set and beating her sister, Venus, in the finals -- right after she discovered she was pregnant. She took maternity leave from the tour in April, but tried to keep up her fitness routine up until the baby's birth.
Williams and Ohanian announced their engagement in December 2016, and the proud papa has been very supportive throughout Williams' pregnancy. The two attended the Met Gala together and took a whirlwind European babymoon -- and Ohanian admitted he was scouring his own website for parenting tips before the baby's birth.
Williams said she intends to return to tennis after the baby is born, writing on Instagram in April that "I can't wait for you to join the players box next year...from the world's oldest number one to the world's youngest number one."
Check out Williams' maternity shoot for Vanity Fairin the video below: