The woman, Pamela Rauseo, was caring for her nephew, a five-month-old baby, when she noticed he was unwell.

She leapt out of her car and cried for help among drivers stuck in traffic on the busy road.

"My sister had trusted me with him," Ms Rauseo, 37, was quoted as saying in the Miami Herald.

Several people stopped to help, starting CPR on baby Sebastian,

A Miami Herald photographer ran along cars to look for help, and found a policeman in a patrol car.

The officer ran over and took over CPR.

Eventually, he and others got the baby breathing again, until emergency workers arrived.

The baby survived and is reported to be in a stable condition in hospital.