One of every 100 babies born in the United States is born with some kind of a congenital heart defect, many of which aren’t immediately obvious but can often be detected with proper screening.

On February 14 doctors and nurses at University of Iowa Stead Family Children’s Hospital began screening each newborn for congenital heart defects using pulse oximetry.

Pulse oximetry is a quick, non-invasive test in which sensors are placed on the hands and feet of newborns to check the amount of oxygen in the blood and the baby’s pulse rate. The test checks for seven forms of congenital heart defects and gives doctors an early sign if additional tests should be done.