The mother said Sarah, who was declining rapidly from end-stage cystic fibrosis, would head into surgery within 30 minutes. She has been hospitalized at Children's Hospital of Philadelphia for three months.
Sarah's family challenged an existing lung allocation rule, prompting the Organ Procurement and Transplantation Network to allow children younger than 12 to petition to be included on adult lists. The decision came just days after a federal judge granted her family's request to suspend a rule that kept Sarah from receiving lungs from an adult donor based on the severity of her illness.
It was not immediately clear whether the donated lungs came from an adult or teen older than 12 or from a child. Sarah had been on the pediatric transplant list since 2011, which allowed her priority allocation for lungs from children.
Transplant experts defended their system, which has been in place since 2005, saying that it matched children with organs appropriate for their age and size and that it allowed teens and adults to be prioritized for transplant based on how sick they were. Some experts argued that the Murnaghan family's challenge would upend a system that had cut deaths on the transplant waiting list by 40 percent. They questioned whether transplant decisions should be made by a judge rather than medical experts.
Nearly 1,700 people nationwide are on the waiting list for lung transplants, including 30 children aged 10 and younger, according to OPTN.
Under U.S. District Court Judge Michael Baylson's order, OPTN placed Sarah on the adult list as of 10:34 p.m. June 5, according to a letter from U.S. Health and Human Services Secretary Kathleen Sebelius.
Janet Murnaghan called Sarah's donor "her HERO, who has given her the gift of life."
"Today their family has experienced a tremendous loss," she wrote. "May God grant them a peace that surpasses understanding."
Art Caplan, director of medical ethics at New York University's Langone Medical Center, said that the Murnaghans' persistence appeared to pay off for their daughter.
"It is wondering that the transplant is proceeding," said Caplan, a frequent NBC News contributor. "The parents really went the extra mile."
But, he added, the system should still rely on medical judgment, not public relations efforts or legal directives, to decide who is the best candidate for any organ.
Experts cautioned that that transplant procedure is difficult and painstaking and could take between six and seven hours. Nearly 80 percent of lung transplant patients survive the first year, but only about half survive five years, according to the National Heart Lung and Blood Institute.