The Oscar winner was found to have a faulty gene which sharply increases the chance of her developing breast and overian cancer.
Jolie, who lives with Hollywood star Brad Pitt, says in an article for The New York Times that her mother fought cancer for 10 years before her death.
She writes: "My doctors estimated that I had an 87% risk of breast cancer and a 50% risk of ovarian cancer, although the risk is different in the case of each woman.
"Only a fraction of breast cancers result from an inherited gene mutation. Those with a defect in BRCA1 have a 65% risk of getting it, on average.
"Once I knew that this was my reality, I decided to be proactive and to minimise the risk as much I could. I made a decision to have a preventive double mastectomy."
Treatment
Jolie, 37, who has six children - three by Pitt and three adopted - goes on: "On April 27, I finished the three months of medical procedures that the mastectomies involved.
"During that time I have been able to keep this private and to carry on with my work. But I am writing about it now because I hope that other women can benefit from my experience.
"Cancer is still a word that strikes fear into people’s hearts, producing a deep sense of powerlessness.
"But today it is possible to find out through a blood test whether you are highly susceptible to breast and ovarian cancer, and then take action."
Malcom Kell is a Consultant Surgeon at the Mater Private hospital in Dublin. He says, "Depending on a number of specific gene abnormalities, and depending on which one you have, we can identify what your lifetime risk will be. So that the one that was at 80%...in the BRCA1 it would go down to at least 5% (after treatment). It's important that any patient having that procedure knows the risk isn't zero but it's certainly dramatically reduced."
Risk reduced
Jolie reveals that she had the first of three procedures on February 2. The major surgery "where the breast tissue is removed and temporary fillers are put in place" was carried out two weeks later.
Nine weeks later she had breast implants. "There have been many advances in this procedure in the last few years, and the results can be beautiful," she writes.
She adds: "I wanted to write this to tell other women that the decision to have a mastectomy was not easy. But it is one I am very happy that I made.
"My chances of developing breast cancer have dropped from 87% to under five per cent. I can tell my children that they don’t need to fear they will lose me to breast cancer."
Others affected
Other celebs who've made similar decisions include US actress Christina Applegate, X Factor judge Sharon Osbourne and former Liberty X star Michelle Heaton - who is married to Irishman Hugh Hanley:
Author and cancer survivor Emma Hannigan spoke to Newstalk's Breakfast. She says she doesn't look any different to the way I did before, but she has eradicted the danger - she says she views it as giving herself life:
