The tennis star seemingly made the slip-up after winning the second round of the French Open on Wednesday.
Sounds like Serena Williams may be having a baby girl!
Although the 35-year-old tennis star, who is expecting her first child with fiancé Alexis Ohanian, has yet to officially reveal the gender of her baby on her own, sister Venus Williams seemingly made a slip-up during her post-match interview with Eurosport after winning the second round of the French Open on Wednesday.
WATCH: Pregnant Serena Williams Looks Fabulous While Babymooning in Monaco
"She's going to call me 'favorite aunt,'" Venus said. "Every day we're like, 'Baby Vee, baby Isher, baby Lyn,' so we all want the baby to be named after us."
Whoops!
Serena -- who cheered on Venus in a white Nike tank top, floral jacket and comfy black leggings -- announced the exciting news that she was pregnant last month, taking to Snapchat to show off her baby bump in a bright yellow bathing suit and captioning it, "20 weeks." But while chatting with Gayle King at the 2017 TED Talks conference at the Vancouver Convention Centre a few weeks later, she revealed she didn't mean to post it to her public story for all to see.
"It was an accident," she said, clarifying why the pic was deleted shortly after it was posted. "I was on vacation just taking some time for myself and I have this thing where I've been checking my status and taking pictures every week to see how far along I'm going."
"I didn't tell a lot of people, to be quite honest, and I'd been saving it," she added. "On social media, you press the wrong button and [it's done]. Thirty minutes later I missed four calls and I'm like, 'That's weird.'"
Hear more in the video below.