Patent ductus arteriosus (PDA) is a heart problem that occurs soon after birth in some babies. While a baby is in the womb it gets oxygen from the mother's bloodstream, after birth, the baby is no longer connected to the mother's bloodstream and therefore needs the blood to go directly to its own lungs to get oxygen. If the ductus arteriosus doesn't close after birth as it should, it's called a patent ductus arteriosus (PDA).