By Mike Fleeman

05/14/2013 at 02:00 AM EDT

Angelina Jolie has revealed she underwent a double mastectomy after genetic tests showed she had a high risk of developing breast cancer.

The 37-year-old actress had the surgery in February and completed the last of the follow-up procedures in April, she says in a New York Times op-ed piece called “My Medical Choice.”

“I wanted to write this to tell other women that the decision to have a mastectomy was not easy,” says Jolie in the column appearing Tuesday. “But it is one I am very happy that I made. My chances of developing breast cancer have dropped from 87 percent to under 5 percent. I can tell my children that they don’t need to fear they will lose me to breast cancer.”

Jolie, who has six children with Brad Pitt, says the actor was at her side every step of the way.

“I am fortunate to have a partner, Brad Pitt, who is so loving and supportive,” she writes. “So to anyone who has a wife or girlfriend going through this, know that you are a very important part of the transition.”

Pitt was with her “for every minute of the surgeries,” and even during the difficult times, “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,” she writes.

Jolie, whose mother, actress Marcheline Bertrand, died at age 56 in 2007 after a long battle with cancer, says tests found she had a “faulty gene.” Doctors gave her an 87 percent risk of breast cancer and a 50 percent risk of ovarian cancer, she says.

Jolie describes in detail her surgery and follow-up procedures, including receiving implants, and that now her children “see nothing that makes them uncomfortable.”

“They can see my small scars and that’s it,” she writes. “Everything else is just Mommy, the same as she always was. And they know that I love them and will do anything to be with them as long as I can.

“On a personal note,” she continues, “I do not feel any less of a woman. I feel empowered that I made a strong choice that in no way diminishes my femininity.”