The woman was on her way to Madrid's San José Clinic with her husband when she realised that the baby wasn't going to wait until the delivery room.
The couple were forced to pullover around the 11km marker on Madrid's A-1 motorway and flagged down a passing Guardia Civil patrol car for some unusual roadside assistance.
The officers stepped in and helped deliver the baby with the help of Samur - Madrid's emergency services and ambulance service - who guided them through over the telephone before an ambulance arrived on scene.
The baby girl was delivered safely and weighed three kilograms, Samur confirmed. Mother and baby were taken to the San José clinic where they were in a good state, the ambulance service confirmed in a tweet.
"I was in the ambulance to check the breathing of both (the mother and daughter) and the birth went perfectly and both were in a perfect state," confirmed Samur ambulance worker Isabel Casado.
The Guardia Civil and Madrid's emergency services were praised by the City Hall for their good work in helping with the birth.
Check out the video below for more images of the dramatic birth.