The baby weighs 8 lbs. and is 21 inches long. She was delivered at 1:36 a.m. in a birthing tub at the couple's home in Malibu, with a midwife in attendance.
"Nichole was a mountain lion, a warrior in the birthing process," McGinley tells PEOPLE. "The birth was astonishing! Mom and baby girl are 100 percent. Billie is a 'mini Nichole'! Thank God."
New mom Nichole, an Ashtanga yoga teacher and birthing doula, adds, "We are all happy and healthy at home and enjoying these precious first moments of life together."
The couple married on April 7, 2007. Billie is their first child together. McGinley also has a 10-year-old son Max.