When Irie Felkner and her twin brother Judah were born prematurely at 27 weeks, their parents knew the first few months wouldn’t be easy. While the twins were fighting for their lives in the neonatal intensive care unit (NICU), hooked up on ventilators, an echocardiogram showed an opening in Irie’s heart had grown too large. Irie was suffering from a life-threatening congenital defect called a patent ductus arteriosus, or PDA, which is an opening between two blood vessels leading from the heart that is also present in normally developing fetuses. For most babies, that opening seals itself shortly after birth. But in some cases — primarily in premature babies such as Irie — it fails to close, making it difficult for babies to breathe normally due to an increased flow of blood to the lungs.