A new study examining thousands of people who’ve had heart transplants as children shows they have an increased risk of suffering from kidney failure later in life.

The study was led by Swati Choudhry, MD, a pediatric cardiology fellow at Washington University School of Medicine in St. Louis.

“A heart transplant is a miraculous, life-saving surgery for patients who suffer from irreversible heart conditions,” Choudhry said in a statement. “Unfortunately, some heart transplant recipients may end up with devastating kidney failure over time, a setback which compromises the quality and the longevity of life for these patients.”

The research can valuable to heart surgeons, considering there were more than 400 heart transplants performed on children in 2016, according to the Organ Procurement and Transplantation Network. And since 1988, there have more than 8,700 heart transplant in children.

Choudry’s team examined 25 years of records from more than 6,900 heart transplant patients from the Scientific Registry of Transplant Recipients and the U.S. Renal Data System.

In the data, investigators found that patients who survived 10 years after a heart transplant had a 3 percent risk of developing kidney failure, compared to 16 percent for those who survived 20 years.

One reason contributing to kidney failure are the two major medications given to patients who have undergone a heart transplant—cyclosporine and tacrolimus.

The researchers wrote in the study that they hope the findings motivate medical professionals to develop safer medications that won’t have detrimental effects on patients.