Hilaria Baldwin tweeted the news from her verified Twitter account Friday night. She says that the family is overjoyed and that Carmen Gabriela "is absolutely perfect."
Publicist Matthew Hiltzik also confirmed the child's birth Friday night.
The former "30 Rock" star already is the father of a 17-year-old daughter, Ireland, from his previous marriage to actress Kim Basinger.
Hilaria Baldwin is a special correspondent for the TV show "Extra." The couple wed last June after a three-month engagement.
On her verified Twitter account, Ireland Baldwin welcomed her new sister into the world and linked to a blog post with 10 pieces of advice for the newborn.