From the state senator's Twitter feed earlier this morning:
From SCD staff: Thrilled to announce that Senator Chang-Diaz delivered a baby girl, Mila, on Saturday. Mom and Mila are both doing great!
— Sonia Chang-Diaz (@SoniaChangDiaz) July 1, 2013 
The details, via an email sent out by Chang-Diaz's chief of staff, Angela Brooks:
On behalf of our office, I am thrilled to announce that Senator Chang-Díaz delivered a baby girl on Saturday afternoon. Milholland Harriet Hirsch Chang-Díaz was born at 4:06 pm, and weighed 8 lbs. 9 oz.
Mom and Mila are both doing great. The Senator is very appreciative of all the well wishes over the last few months, and is happy to have Mila here!