Did Serena Williams just let slip best friend Meghan Markle is having a GIRL?!

Serena Williams could be in trouble! Looks like she inadvertently let slip that Prince Harry and Meghan Markle are having a girl!

Oops.

The 37-year-old tennis player, who has a one-year-old daughter, Alexis Olympia, was being interviewed by E! News when she was asked to give her advice for new mothers.

That's when Serena referenced a friend of hers who is currently pregnant — and referred to that friend's baby as 'she.'

Serena's advice to new mums was very sensible and she said, 'Accept mistakes and don't expect to be perfect. We put so much pressure on ourselves.

'My friend is pregnant and she's like, "Oh, my kid's gonna do this," and I just looked at her and I was like, "No, she's not." I'm like, "No, you're not,"' she said.

While Serena didn't name the friend as 37-year-old Meghan Markle, the Duchess of Sussex, they are best friends and Serena just threw her a baby shower in New York!  

At that baby shower there were hundreds of pale pink roses, suggesting the baby is a girl. 

 She also admitted later in the video that she had no concerns about Meghan's new role as a mummy.

'She'll be the best mum, to be sure,' she said. 

Serena has been a good friend for Meghan throughout her pregnancy, even sending her nappies!

The tennis legend has teamed up with Pampers as a spokesperson for the brand, and while speaking with Reuters about the collaboration, she admitted she 'already sent Pampers across the pond.'

See the video here!