There was no official confirmation from Williams or her management but, asked how it felt to become an aunt again ahead of her third-round US Open match, Serena's sister Venus told ESPN: "Obviously I'm super excited".
Williams later addressed her mistake and clarified that she had only announced the pregnancy a few days earlier than planned.
Hopefully her daughter will be cheering with Ohanian in the stands. Williams last month told Vogue in a wide-ranging interview that she had set herself a goal of returning to play in Melbourne at next year's Open.
"Words can't describe", she said.More news: Arsenal will not accept cash offer for Alexis Sanchez
"I don't know what to do with a baby".
She added: "If you would have told me past year in October or November that I would have a baby, not be pregnant but have a baby, I would have thought you were the biggest liar in the world".
"If she puts her tennis second, she might be not as good as she could be and this she will not accept". "I'm not a spring chicken". "It was a relief of course because, as a first responder, you want to save lives - and that's what I thought I had done".
But the other important details about Serena Williams' baby - including her name and pictures - have yet to be revealed. Margaret's won 24 singles titles and I think Serena would like to break that, at least break the singles record of 24 majors. "It's going to be something incredibly impressive to go through".
The couple first announced the pregnancy by accident back in April when Williams uploaded a photo of her baby bump to Snapchat by mistake. In June, she talked to Vanity Fair about the fear and excitement she had surrounding her pregnancy.