Sarah Murnaghan Celebrates 12th Birthday

Sarah was 10 when her family fought the "Under 12 Rule" to save her life.

-- Sarah Murnaghan put her new lungs to good use this weekend, blowing out the birthday candles on a yellow cake while her siblings sang “Happy Birthday to You” – the cha-cha-cha version.

Sarah, whose family fought the “Under 12 Rule” last year to help her get a double-lung transplant from an adult donor, has turned 12.

“Today Sarah turned 12!” her mother, Janet Murnaghan, wrote on the Sarah’s Heroes Facebook page Aug. 7. “We are so proud of all she has overcome and the progress she continues to make.”

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Sarah received a double-lung transplant June 12, 2013, but it failed. Three days later, she received a second lung transplant. Both came from adult donors.

She celebrated her 11th birthday at Children’s Hospital of Philadelphia and returned home to Newtown Square, Pennsylvania, in late August 2013.

By March, Sarah was back on her pink bike, and on the anniversary of her transplant, she had her tracheostomy tube removed from her neck.

“She no longer needs any assistance to breathe,” Janet Murnaghan told ABC News at the time. "She rides her bike, goes to the pool, out to dinner with the family, museums, parks, etc. She is enjoying life."