When Angelina Jolie announced in 2013 she was having a double mastectomy to reduce her risk of developing breast cancer, some doctors reported a worrying rise in women requesting the same, just in case, even if the surgery wouldn't necessarily help them. Now, Jolie's announcement Tuesday she had surgery to remove both her ovaries and Fallopian tubes to reduce her risk of ovarian cancer raises the possibility of having the same effect. But just how effective is this surgery?

Quite effective, it turns out, if you're a woman of a certain age with a certain family medical history or with certain genetic mutations. But having ovaries and Fallopian tubes removed won't prevent ovarian cancer in every woman. 

The technical term for the specific surgery Jolie underwent is a mouthful: salpingo-oophorectomy. It means the surgical removal of a woman’s Fallopian tubes and ovaries when those organs have no signs of cancer. The National Cancer Institute says women who have a high risk of developing breast or ovarian cancer -- those who have inherited certain genetic mutations or have a family history of these cancers, both of which apply to Jolie -- will often opt to have this procedure. But, the institute warns, “It is very important to have a cancer risk assessment and counseling before making this decision.” 

For women whose heightened risk of ovarian and breast cancer is clear thanks to certain genetic mutations, preventative surgery of the kind Jolie had can seriously reduce their odds of developing ovarian cancer. One medical study called salpingo-oophorectomy “the optimal risk-reducing strategy for women at high risk” of ovarian cancer.

But there are caveats. The surgery is recommended for women between the ages of 35 and 40, and only after a woman is certain she does not want to have children beyond that point. Removing the ovaries inevitably changes a woman's hormones, and so the surgery can cause early menopause, which in itself tends to be uncomfortable and can also lead to osteoporosis, or bone thinning, which means a greater likelihood of broken bones.

Even if women have their ovaries removed, it’s still possible for them to develop ovarian cancer in the peritoneum, a layer of tissue along the abdomen, if cancer cells from the ovaries spread there before surgery or if not all the ovarian tissue is removed.

For women who don't have a clear genetic risk of developing breast cancer or ovarian cancer, such radical surgery shows no evidence of being effective. Nevertheless, at least one study has shown some women will undergo such surgery anyway, even if they don’t have the specific genetic mutation. In a survey, 12.3 percent of women whose tests did not show they had the mutation opted to have their ovaries and Fallopian tubes removed, the study noted. For these women, the study found there was “insufficient data to determine the effectiveness of these interventions.” 

Of all the salpingo-oophorectomies that are performed every year in the U.S. or around the world, it's not clear what proportion are carried out on women who have no clear risk of ovarian or breast cancer, and it's too soon to tell what impact Jolie's announcement could have on the numbers of women flocking to hospitals to have the same procedure. In 2010, calculations based on the National Hospital Discharge Survey suggest oophorectomies and salpingo-oophorectomies represented about 20 percent of all operations on female genital organs.