On Monday, the couple announced that they are expecting a second child.
Olivia made the grand reveal on Instagram while posing for a photo with the couple's insanely adorable son, Otis.
"Matching baby bumps," she captioned the black and white snap of her and Otis holding their bellies. Both mom and son smile widely as they reveal that Otis, who turns 2 this week, is going to be a big brother.
Speculation that Olivia was pregnant had been rumored for a few weeks. She's been vocal about her desire to add to her brood, as well.
Earlier this month, she told People that she and her fiance were ready for another child.
"I'm desperate for more [kids]!" she said. "I love my siblings so much and Jason has incredible siblings too. The more the merrier."
In January, the hardly credible Star Magazine speculated that she was pregnant because she was "covertly" covered up at a party.
The report, which bared the not-so-graceful headline "Bump Or Burger," also said that Olivia avoided alcohol at a Golden Globes party.
The report prompted the actress to take to Twitter to hilariously shoot down rumors, saying that the only "bun" in her oven came from a restaurant or at-home cooking. She even posted a photo from the magazine touting her alleged pregnancy.
"Sorry, Star mag, but you got us confused with the cooler version of us. Congrats to John and Emily!," she wrote, referring to the pregnancy announcement of their pals John Krasinski and his wife Emily Blunt. "My bump is all [burger.]"
In late February, Olivia gushed about motherhood, saying that she's a better person because of Otis.
"It's made me a better human being, it's made me a better artist, it's made me a more grateful person, a more tired person. Everything it does to every single mother, that's the most amazing thing about it."
She continued, "You become a mother and you go through kind of the same experience. I kept thinking about that during child birth and I think about it every day since.
"It's just something that unites us and that's a really, wonderful, powerful thing so I want to channel that into a role that would be help me be really helpful in some way."