Angelina Jolie has undergone preventive surgery to have her ovaries and fallopian tubes removed, just two years after having a double mastectomy.
The actress emotionally revealed that she made the decision after doctors said she was at an increased risk of developing ovarian cancer.
Writing in The New York Times, the mother, who carries a mutation in the BRCA1 gene, said the decision was "not easy".
"In my case, the eastern and western doctors I met agreed that surgery to remove my tubes and ovaries was the best option, because, on top of the BRCA gene, three women in my family have died from cancer," she said.
"My doctors indicated I should have preventive surgery about a decade before the earliest onset of cancer in my female relatives.
"My mother's ovarian cancer was diagnosed when she was 49. I'm 39.
"It is not possible to remove all risk, and the fact is I remain prone to cancer.
"I will look for natural ways to strengthen my immune system. I feel feminine, and grounded in the choices I am making for myself and my family. I know my children will never have to say 'Mom died of ovarian cancer'."
Jolie said she had been planning the surgery "for some time" and had been preparing herself "physically and emotionally" for the operation, which puts a woman into forced menopause.
However, the procedure became urgent two weeks ago when her annual blood test results showed she could be in the early stages of cancer.
Speaking of the moment her doctor revealed his fears, she said: "I went through what I imagine thousands of other women have felt. I told myself to stay calm, to be strong, and that I had no reason to think I wouldn't live to see my children grow up and to meet my grandchildren.
"I called my husband in France, who was on a plane within hours. The beautiful thing about such moments in life is that there is so much clarity. You know what you live for and what matters. It is polarising, and it is peaceful."
While further tests found her chances of having cancer were minor, she decided to press ahead with the operation last week.
Doctors have since since found "no signs of cancer in any of the tissues", she said.
"It is not easy to make these decisions," she added.
"But it is possible to take control and tackle head-on any health issue. You can seek advice, learn about the options and make choices that are right for you.
"Knowledge is power."
Jolie opted to have a double mastectomy in 2013 after she first discovered she carried the faulty gene, which put her likelihood of developing breast cancer at 87%.
The operation cut that risk to just 5%.
The gene is also associated with ovarian cancer, which killed the UN ambassador's mother, Marcheline Bertrand, in 2007.
But the actress-turned-director said that carrying the gene does not mean "a leap to surgery", adding "I want other women to hear this".
Instead, she considered other options, advice from doctors and her own family history before choosing to have her ovaries and fallopian tubes removed.
"There is more than one way to deal with any health issue," she said.
"The most important thing is to learn about the options and choose what is right for you personally."
Jolie has been praised in the past for opening up discussions around women's health and sparked a doubling in referrals for genetic breast cancer tests in the UK last year, in what doctors dubbed the "Angelina effect".