What is Hydrops Fetalis?

Hydrops fetalis, or fetal hydrops, is a condition in fetuses or newborn children in which abnormal and potentially dangerous amounts of fluid accumulate in the heart, lungs or abdomen or beneath the skin. For hydrops fetalis to be diagnosed as such, at least two of these spaces must affected by accumulated fluid. This condition can be caused by anemia, congestive heart failure and obstruction in the lymphatic system. Symptoms of hydrops fetalis include skin bruising, swelling of the liver, severe jaundice, difficulty breathing, severe anemia and heart failure.

The fetus is particularly vulnerable to changes in fluid production and circulation, and therefore to fluid accumulation. This vulnerability is present because fetal capillaries are more permeable, meaning that fluid can move in and out more readily. When disease such as anemia or heart failure cause the heart to become less efficient, the heart must work harder to distribute oxygen. The result of this is increased pressure on veins, increased permeability of capillaries and an increased tendency for fluid to build up in certain locations.

The most common cause of hydrops fetalis is anemia, characterized by reduced blood oxygen levels. This condition reduces the efficiency of the heart and causes it to work harder. Fetal anemia can be caused by genetic defects and heart or lung problems. Another cause of fetal anemia is Rhesus incompatibility between the pregnant woman and the fetus she is carrying.

Rhesus incompatibility is caused by blood group differences between the pregnant woman and the fetus. There is a risk of Rhesus incompatibility occurring when a pregnant woman is negative for Rhesus factor and the fetus is positive for Rhesus factor. In this situation, the woman’s immune system can attack the baby’s red blood cells, causing severe anemia. Rhesus incompatibility can be avoided with immunotherapy medication that prevents the woman’s immune system from attacking red blood cells.

Hydrops fetalis usually is diagnosed during an ultrasound, a test that is carried out several times during a typical pregnancy to screen for this and other problems. If a fetus is affected by hydrops, an ultrasound will show excess amniotic fluid in the uterus and a larger-than-normal placenta. The ultrasound also will pinpoint areas where excess fluid has accumulated in the fetus.

Treatment for fetal hydrops depends on the cause of the condition and whether hydrops is present before or at birth. If the condition is diagnosed before birth and the fetus is old enough to survive outside the uterus, early labor can be induced. If this is not possible and the hydrops is caused by anemia, the fetus might be given an intrauterine blood transfusion.

After birth, the newborn infant receives additional treatment. When the cause is congestive heart failure, for example, treatment includes medication to help remove excess fluid from the body to ease the strain on the heart and kidneys. If the condition is caused by anemia, the baby is given one or more blood transfusions to replace lost red blood cells.