Angelina Jolie has had a preventive double mastectomy and has paid tribute to her ''loving and supportive'' partner Brad Pitt..

The Hollywood star said she took the decision to have the procedure when doctors told her she had an 87% risk of breast cancer and a 50% risk of ovarian cancer.

Writing in The New York Times, the Tomb Raider actress said she finished the three months of medical procedures on April 27, and added: ''During that time I have been able to keep this private and to carry on with my work.''

Paying tribute to Pitt, Jolie said: ''I am fortunate to have a partner, Brad Pitt, who is so loving and supportive.

''So to anyone who has a wife or girlfriend going through this, know that you are a very important part of the transition.

''Brad was at the Pink Lotus Breast Centre, where I was treated, for every minute of the surgeries.

''We managed to find moments to laugh together. We knew this was the right thing to do for our family and that it would bring us closer. And it has.''

The 37-year-old star said she was writing about the ordeal, in an article titled My Medical Choice, in the hope that other women can benefit from her experience.

Jolie, whose mother had cancer and died at 56, said waking up from the operation can feel ''like a scene out of a science-fiction film'' .

She said the decision to have the mastectomy was not easy but that she was happy to have gone ahead with it.

Urging women to get checked out, the star said: ''For any woman reading this, I hope it helps you to know you have options.

''I want to encourage every woman, especially if you have a family history of breast or ovarian cancer, to seek out the information and medical experts who can help you through this aspect of your life, and to make your own informed choices.''

Former X Factor judge Sharon Osbourne revealed last November that she had undergone the same operation.

Osbourne, 60, had already battled colon cancer a decade ago and took the decision after finding out she carries a gene which increases the risk of developing breast cancer.

In an interview at the time, she said: ''As soon as I found out I had the breast cancer gene, I thought: 'The odds are not in my favour'.

''I've had cancer before and I didn't want to live under that cloud: I decided to just take everything off, and had a double mastectomy.''