"They understand that going through medical challenges and fighting to survive and heal is something to be proud of."

Angelina Jolie says two of her daughters have recently had "medical challenges" in the past two months, with both of them undergoing surgeries.

In an essay for Time, the actress and humanitarian wrote that 15-year-old Zahara and 13-year-old Shiloh have both gone through surgery, writing that Shiloh underwent a hip surgery, though she did not go into detail about Zahara's procedure.

"I have spent the last two months in and out of surgeries with my eldest daughter, and days ago watched her younger sister go under the knife for a hip surgery," she wrote. "They know that I am writing this, because I respect their privacy and we discussed it together and they encouraged me to write. They understand that going through medical challenges and fighting to survive and heal is something to be proud of."

Angelina Jolie with childen
Angelina Jolie with children Vivienne Marcheline Jolie-Pitt, Zahara Marley Jolie-Pitt, Shiloh Nouvel Jolie-Pitt and Knox Leon Jolie-Pitt.
| Credit: Photo by Ian West/PA Images via Getty Images

Jolie described watching her daughters care for one another, and said that as she spent International Women's Day writing the essay from the hospital, "I find myself focusing on my daughters for a moment, and all that I have learned from them and other young girls I have met around the world."

Jolie concluded her essay by appealing to readers to value and care for girls, to "know that the stronger they grow, the healthier they will be and the more they will give back to their family and community."

"And my message to girls is, fight on, little ladies," she wrote. "Your care for each other will be a large part of your way forward. Hold your nerve. Know your rights. And never let anyone tell you that you are not precious and special and, above all, equal."

Jolie shares six children —11-year-old twins Knox and Vivienne, 11, 16-year-old Pax, and 18-year-old Maddox, alongside Zahara and Shiloh — with ex-husband Brad Pitt.

She was recently spotted with Zahara and Shiloh at Cirque du Soleil in Los Angeles, where they met with the cast of the touring show backstage.

To get our top stories delivered to your inbox, sign up for the Healthy Living newsletter

This article originally appeared on InStyle.com