Sarah Murnaghan, the 10-year-old Pennsylvania girl dying of cystic fibrosis, is receiving her long-awaited lung transplant.

According to a Facebook post from Sarah's mother, Janet, the family received word this morning of new lungs that had been made available, and Sarah will be taken to the operating room within the next 30 minutes.  The operation will take many hours.

In the Facebook post, Janet asked her followers to pray for Sarah's donor.

"Please pray for Sarah's donor, her HERO, who has given her the gift of life," Janet Murnaghan wrote. "Today their family has experienced a tremendous loss, may God grant them a peace that surpasses understanding."

Sarah has been in desperate need of a lung transplant for the past 18 months.  However, under the current guidelines for organ donation, children under the age of 12 must wait for pediatric lungs to become available.  Adult lungs cannot be offered to children under 12, until they are offered to adults and adolescents first.

The Murnaghans have been in the middle of a legal battle over the established rules for organ donation, after they filed a lawsuit last week to have the guidelines changed, arguing the rule keeping Sarah off the list is "discriminatory."

A federal court judge granted a temporary order on June 5 that allowed Sarah to join an adult organ transplant list. It is not yet clear whether Sarah's donor is an adult or a child.

Over the weekend, Sarah's condition worsened, and she had to be intubated on Saturday after she experienced additional trouble breathing.

This story is developing.