Kristen Bell and Dax Shepard welcomed their second child Delta on Dec. 19. Credit: Jason Kempin/Getty Images

Lincoln's a big sister! Kristen Bell and Dax Shepard have welcomed their second baby girl together. The couple announced the news via Twitter on Friday, Dec. 19.

"Delta Bell Shepard is here. She doesn't look like either ?@IMKristenBell? or me, but we're gonna keep her anyway. ?#christmascameearly?" Shepard tweeted

The proud mom also tweeted, "The estrogen has now hit critical mass! Good luck, @daxshepard1.  And welcome to the world DELTA BELL SHEPARD :)"

Us confirmed in June that Bell, 34, and the Parenthood actor, 39, were expecting again. "The whole family is beyond excited," a rep for the couple told Us at the time.

During her "really easy" pregnancy, Bell gave Us new insight about daughter Lincoln, 20 months. "She can sign now and she knows 40-50 signs! I can talk to her and she'll sign in three, four word sentences which is really amazing," the Veronica Mars alum told Us in September. "She's the smartest baby ever!" she joked.

Bell, who filmed adorable Samsung commercials with Shepard while pregnant, also gushed about Lincoln at the This Party Saves Lives event in L.A. on Oct. 16. "She's very interested in the shape of my belly. Very interested in offering it water and crackers and giving it smooches," she told Us. "She could just be mimicking what we're doing but I have a hunch she knows what's happening."

Bell and Shepard tied the knot in October 2013.

Tell Us: Do you like the name Delta?