A serious condition in which extra fluid builds up inside a fetus or newborn.

Hydrops fetalis happens when extra fluid builds up in two or more compartments of a fetus or newborn. There are two types. Immune hydrops fetalis occurs when the fetus' blood type is not compatible with the pregnant parent's. Nonimmune hydrops fetalis is more common. Its causes include heart or lung conditions, anemia, or developmental conditions.

Symptoms depend on how serious the condition is. Hydrops fetalis may cause liver swelling and changes in skin color. When the condition is more serious, symptoms may include trouble breathing, heart failure, bruising and severe anemia.

Treatments for newborns may include medicines, blood transfusions and breathing support.