Media playback is unsupported on your device Media caption Good Morning America's Amy Robach found out she had breast cancer while filming a report for the show

Good Morning America's Amy Robach has revealed she will have a double mastectomy this week, a month after undergoing a mammogram on the show.

The 40-year-old correspondent discovered she had breast cancer after reluctantly agreeing to have a screening filmed for the ABC show.

She said GMA anchor Robin Roberts had persuaded her that if the story saved one life, it would be worth it.

"It never occurred to me that life would be mine," said Robach.

Producers chose Robach to cover the mammogram story because it is recommended that women at the age of 40 regularly check for breast cancer.

During Monday's programme, and in a blog post following the show, Robach said doctors had not yet determined what stage the cancer had progressed to, or whether it had spread.

The original story, which was part of the GMA Goes Pink breast cancer awareness day, featured Robach emerging from her on-air mammogram, before telling colleagues that it hurt much less than she thought it would.

A few weeks later she was told she had cancer, after returning for what she thought would be some follow-up images.

Robach said that her husband, actor Andrew Shue, had returned from his work trip that night and her parents had also caught a flight to New York to join her.

"We started gearing up for a fight," she said, as she revealed that she would have both breasts removed this Thursday, followed by reconstructive surgery.

Robach joined ABC in 2012 from NBC, where she was a Weekend Today host.

'No excuses'

She frequently filled in as a presenter on ABC's top-rated morning show GMA, while host Roberts was fighting a serious blood and bone marrow disease.

Robach said that with a full-time job and two children she had always found reasons to put off having a mammogram herself.

However a doctor told her that the test had saved her life.

"I can only hope my story will inspire every woman who hears it to get a mammogram, to take a self-exam," said Robach.

"No excuses. It is the difference between life and death."