Oglesby gave birth to daughter Breeze Beretta Johnston on Wednesday (September 12), reports TMZ.
She apparently delivered in the couple's hometown of Wasilla Alaska at Matsu Regional Hospital.
Baby Breeze weighed in at six pounds and was 19 inches at the time of her birth.
The couple announced Oglesby's pregnancy in April, with Johnston saying at the time that he is "in love" with his partner.
Johnston also has a 3-year-old son named Tripp with former fiancée Palin. He and Palin split in August 2010.