"Blake and Ryan aren't finding out what they're having," a source told UsWeekly. "They want to be surprised!"
And while the suspense would prove too much for some mums and dads-to-be, it seems that Blake is content to remain in the dark as to whether she's expecting a little girl or a boy.
"She is [feeling] super relaxed and mellow," the source added.
Blake, 27, shared that she and handsome hubby Ryan are expecting their first child together on her lifestyle website Preserve at the beginning of October.
In a post entitled "Preserve Celebrations: Falling for family," the former Gossip Girl actress shared a photo of her growing baby bump.
The sweet snap showed Blake in the very early stages of her pregnancy, flaunting her changing body in a printed skirt and cradling her blossoming tummy.
The website post spoke about the "family" Blake had built, referring to her company, and gave a special mention to the women responsible for creating families.
"Today we celebrate them," the message read, before adding at the end, "Congratulations to all the expecting mothers out there."
The blonde beauty has since been seen showing off her maternity style and joking that she's keeping things very practical.
"Have you seen me?!" she laughed to People magazine recently when asked about her baby bump. "I'm going to amp up my style by wearing things that are stretchier, because that’s all that fits!"