Over more than 60 years, one man saved the lives of 2.4 million babies.

Every fortnight for more than 60 years, James Harrison has made his way to the Red Cross blood bank and donated blood.

But this is no ordinary blood donation.

In a regular blood donation, three lives could be saved, while a plasma donation could save 18 lives.

But in 81-year-old James Harrison’s unique case, his blood has helped saved the lives of 2.4 million babies.

James’ plasma contains a rare antibody that is used to make a medication known as Anti-D, which protects unborn babies from Rhesus D Haemolytic Disease (HDN).

Known as the man with the golden arm, James’ blood is so in demand, he’s made 1173 blood donations since 1957.

On Friday, James made his final benefaction, as he retired from donating blood.

“It’s a sad day for me. The end of a long run,” the Central Coast-based man said while donating blood at Sydney’s Town Hall Donor Centre.

“I’d keep going if they’d let me,” he said.

On his last day in the donating chair, half a dozen Anti-D babies and their mothers came to the Donor Centre to personally thank James.

HDN is a potentially deadly condition that can arise if babies have an opposite blood type to their mother.

If a pregnant woman with an Rh negative blood type is carrying a baby with an Rh positive blood type, her body may register the baby as a foreign threat and try to destroy the 'invader' by producing antibodies, as if it is fighting off a virus.

HDN can cause miscarriages, stillbirths and cause brain damage in newborn babies.

James Harrison decided he wanted to start donating blood after blood donations saved his life at the age of 14 when he underwent major chest surgery, requiring 13 litres of blood.

When he started donating in 1954, it was discovered that his blood contained unusually strong antibodies. The discovery of these antibodies later led to scientist's development of the life-saving medication, Anti-D.

Before the breakthrough Anti-D discovery in the 1960s, HDN killed thousands of Australian babies.

Now, every ampule of Anti-D ever made in Australia has a part of James Harrison in it, according to Robyn Barlow, the Rh program coordinator.

"It's an enormous thing... He has saved millions of babies. I cry just thinking about it," said Robyn, who recruited James, the program's first donor.

HDN still has the potential to affect one in six newborns in Australia, with roughly 17 per cent of pregnant women receiving Anti-D – James' daughter has even received Anti-D while pregnant.

Australia's Anti-D program relies on just 160 blood donors.

As he makes his final donation, James firmly urges people to donate blood: "It really is the gift of life. It's so important."