Hydrops fetalis

Gross edema (swelling), usually with anemia, of the fetus. It can be due to Rh blood group incompatibility, in which antibodies crossing the placenta from the mother destroy the red blood cells of the fetus. It can also be caused by a lethal form of the genetic disorder thalassemia, alpha thalassemia, in which alpha-chain polypeptides needed to make fetal or adult hemoglobin are not produced. See also Rh incompatibility; thalassemia, alpha.

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hydrops fe·tal·is or Brit hydrops foe·tal·is -fē-'tal-əs n serious and extensive edema of the fetus (as in erythroblastosis fetalis)

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severe oedema that develops before birth. The excess fluid collects in the body cavities, particularly in the peritoneal cavity (see ascites) and the pleural cavity. There are several causes for this, but the most common is severe anaemia associated with haemolytic disease of the newborn. It can occur with a twin-to-twin transfusion. Other causes are congenital heart disease, kidney disease, and lung disease. Treatment can be undertaken before birth with intrauterine blood transfusions to the fetus; without treatment the mortality is high. Antenatal ultrasound scanning enables early recognition of hydrops fetalis.