There's no information about the name yet, but Kardashian made the announcement on her blog.
Kardashian wrote that their new daughter was born on January 15 at 12:47a.m. and that she weighs a healthy 7 pounds and 6 ounces. She continued:
Kanye and I are happy to announce the arrival of our healthy, beautiful baby girl. We are incredibly grateful to our surrogate who made our dreams come true with the greatest gift one could give and to our wonderful doctors and nurses for their special care. North and Saint are especially thrilled to welcome their baby sister.