An elderly Australian known as "the man with the golden arm" is credited with saving the lives of 2 million babies because of an anomaly inside his veins.

Central Coast man James Harrison's, 78, lifelong blood donations have provided necessary antibodies to fight the deadly rhesus disease that can kill babies in the womb.

The priceless liquid can be traced back to a childhood operation to remove one of Mr Harrison's lungs.

"In 1951, I had a chest operation where they removed a lung — and I was 14," Mr Harrison told CNN .

"When I came out of the operation, or a couple days after, my father was explaining what had happened.

"He said I had (received) 13 units (litres) of blood and my life had been saved by unknown people. He was a donor himself, so I said when I'm old enough I'll become a blood donor."

In Mr Harrison's blood doctors found a rare blood type that carried rhesus-negative cells which had never been seen before which, according to the Red Cross, would go on to save millions of lives from the disease.

"In Australia, up until about 1967, there were literally thousands of babies dying each year, doctors didn't know why, and it was awful," said Jemma Falkenmire of the Australian Red Cross Blood Service.

The disease would attack in utero babies when the 17 percent of mothers with rhesus-negative blood were paired with a father with rhesus-positive blood.

The mother's blood cells would attack the different blood cells in the foetus," Ms Falkenmire said.

"Women were having numerous miscarriages and babies were being born with brain damage.

"Australia was one of the first countries to discover a blood donor with this antibody, so it was quite revolutionary at the time."

Doctors are still not certain why Mr Harrison is one of a small number of people to carry the antibody, but they believe it resulted from the multiple transfusions he received when he was a teen.