Persistent Pulmonary Hypertension in the Newborn
Persistent pulmonary hypertension (PPHN) happens in newborn babies. It occurs when a newborn’s circulation continues to flow as it did while in the womb. When this happens, too much blood flow bypasses the baby’s lungs. This is sometimes called persistent fetal circulation.

During pregnancy, a fetus' lungs don’t exchange oxygen and carbon dioxide. So the fetus only needs a small amount of blood to keep the tissues healthy. A fetus' circulation sends most of the blood away from the lungs. It sends it through connections in the heart and large blood vessels.

After babies are born, this circulation changes when they start to breathe air. The change in pressure in their lungs helps close those fetal (prebirth) connections. This redirects blood flow so that blood is pumped to their lungs. This helps with the exchange of oxygen and carbon dioxide.

If a newborn has low oxygen levels or trouble breathing, these normal changes may not happen. This causes the baby's circulation to continue to direct the blood away from the lungs. The blood pressure in the baby’s lungs stays high. This is PPHN.