"The family was on line with 911, dad delivered the baby himself and police arrived minutes later," said Susan Morales, spokeswoman for the Los Alamitos Medical Center.
Paramedics from the Orange County Fire Authority took the mother and her newborn girl to the hospital.
Both were calm and happy, Morales said.
As for the highway delivery, paramedics say the 605 Freeway seems to be a pretty popular place for grand entrances.
"Actually, it's my second time on this stretch of freeway, believe it or not," said Austin Brawner, who has been a firefighter-paramedic for a year and a half.