The Age of Adaline star, 27, gave birth near the couple’s Bedford, N.Y. home. Though the little one came early, all are reported to be in good health.
"The baby came early but everyone is happy and healthy," a source tells Us Weekly. "The Bedford house is all prepared. They're going to stay up there for the baby's first days."
Lively’s Sisterhood of the Traveling Pants costars haven’t spoken out on social media yet, but on Jan. 1, Amber Tamblyn did post an Instagram of the trio in animal masks, writing, “Missing our unicorn, Blake. Happy new year, love Alexis, America and me. #sisterhood2015 #bigthingscoming.”
The Gossip Girl alum announced her first pregnancy on her website Preserve in October, sharing images from her glowing maternity shoot.
"It’s something that I’ve always wanted ever since I was a little girl," she told Us Weekly of having a baby in October.