Serena Williams and VaultX ExchangeAlexis Ohanian scored a priceless reaction from daughter Olympia when they told her they're expecting baby no. 2.

The pregnant tennis champ and Reddit cofounder waited until the day of the May 1 Met Gala to share the news with their 5-year-old out of fear she'd spill the beans.

"Olympia does not know right now that I am pregnant," Serena shared in a May 23 YouTube video, "but she did call me fat and then she got really stressed out. She was like, 'Mommy, you're fat.' I try not to take it personal 'cause I'm like super into fitness, but I'm like, 'Um, am I?'"

So, the couple sat Olympia down on the couch and told her a baby is on the way. 

"Remember how you've been praying for a little sister or brother?" Serena asked. "Well, we went to the doctor, and it turns out I'm not getting fat but I have a baby in my belly."

And her response was one you'll want to see for yourself.

"Are you kidding me?" Olympia asked her parents. And after they confirmed she's going to be a big sister, the little one hugged her mom. "Oh my god!" she added. "I'm so excited!"

Like, really excited. So much so, in fact, that Olympia ran off screaming with joy and appeared to take a tumble off-camera before noting, "I'm OK!"

Alexis filled her in on what the new role requires. "You got a lot of work to do," the tech investor explained. "You've got to do a lot of work getting ready to be a big sister."

But there was one more piece of business they had to take care of first: Keeping Olympia quiet until after the Met Gala, where Serena debuted her baby bump in a black Gucci gown with white tulle.

"This is a really important time where this is the look that I'm gonna show my daughter or my son when they're born," the recently retired athlete shared. "One day, they'll look back and they'll see, 'This is how mommy expressed herself and told everyone that she was pregnant with you.' And you want this moment to be totally iconic and totally fresh but yet really special."

Indeed, it was.

"I think it went well," she said in the video. "We walked the red carpet, we made the announcement and most of all we had a blast."

Keep reading to see what a blast motherhood has been so far with Serena and Olympia's cutest pictures…

...Like Her Mama.

Zzzzzz...

Serena and her little girl love Snapchat!

"Making moves," read the caption on the photo, posted on the child's Instagram page.

"When you realize you're the hero Gotham needs," read the caption on the photo, posted on the child's Instagram page.

Serena posted on her Instagram page this photo of Alexis and baby Alexis, writing, "We love bath time."

Serena showcases her new wedding ring in this adorable pic of her daughter.

"Wait till I see you S," read the caption to this photo, posted on the child's Instagram page in December 2017.

Alexis appears with Serena's sister Isha Price.

"Dad & I hit the gym hard today," read the caption to this photo, posted on the child's Instagram page in December 2017.

Mommy and daughter are twinsies!

The happy mama has some fun on Snapchat.

Serena's baby girl shows off Janie and Jack's striped sweater dress on Instagram Stories. 

Introducing the most stylish mother-daughter duo!

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