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Mysterious edema revealed: How does fetal edema form?
Fetal hydrops is a condition in the fetus characterized by fluid accumulation, or edema, in at least two fetal compartments. This is different from the accumulation of excess fluid in the chorionic follicles or amnion, which is called chorionephrosis or amniotic edema. Specific manifestations of edema may include areas such as the subcutaneous tissue (especially in the scalp), chest cavity (pleural fluid), pericardium (pericardial effusion), and abdomen (ascites). This condition is often caused by the fetus's heart being unable to keep up with the high blood flow demands, leading to heart failure.
Edema is, in a sense, a prenatal heart disease, indicating that the fetus is facing very high blood circulation demands.
Causes of hydrops fetalis
The main cause of hydrops fetalis is usually anemia in the fetus, which requires the heart to pump blood at a higher rate to keep up with oxygen demand. The formation of fetal anemia has both immune and non-immune possibilities. Nonimmune edema is sometimes not associated with anemia, such as certain fetal tumors or congenital pulmonary airway malformations that lead to increased blood flow demand.
Immune Pathophysiology
The only immune cause of hydrops fetalis is Rh disease, called erythroproliferative fetal disease. Incompatibility of blood types between the pregnant woman and the fetus may cause the mother to produce antibodies against the fetal red blood cells, which will cause the fetal red blood cells to lyse and lead to anemia. As the pathological condition worsens, the mother's immune response becomes increasingly stronger, exacerbating the formation of anemia, hepatomegaly, and edema in the fetus.
The incidence of Rh disease has dropped significantly due to preventive measures developed in the 1970s, but a small number of pregnant women remain susceptible to Rh disease after receiving prevention.
Non-immune pathophysiology
The causes of non-immune edema include severe anemia, rapid circulation, etc. Overworking the heart can cause one side of the heart to fail, which can lead to pulmonary edema. Accordingly, failure of the right side of the heart leads to an increase in the body's venous blood pressure, causing peripheral edema and ascites. Nonimmune hydrops fetalis has many causes, including iron deficiency anemia, congenital heart disease, and infection (such as that caused by parvovirus or cytomegalovirus).
Diagnostic Methods
The diagnosis of fetal hydrops is usually made by ultrasonography, with the official diagnosis being the presence of excess serum fluid (such as ascites or pleural effusion) in at least one space with associated skin edema (greater than 5 mm); or hydrops fetalis without associated edema. Excess serum fluid was found in two potential spaces in the case.
Prenatal ultrasound scanning enables early recognition of hydrops fetalis and has been enhanced with the introduction of MCA Doppler.
Treatment options
Treatment of hydrops fetalis depends on its cause and the stage of pregnancy. For fetuses with severe anemia, especially those with Rh disease and α-thalassemia, blood transfusion therapy can be performed in the mother's body. If infection of the fetal sac causes anemia, additional testing and treatment may be needed.
After detailed analysis, measures such as laser ablation or selective termination of pregnancy may also be considered for pregnant women with twins, which aim to address the uneven blood supply between the fetuses.
Of course, the treatment of fetal hydrops is a complex process that requires comprehensive consideration, and the possible impact on the future is also thought-provoking. How to better prevent and treat this condition remains a major challenge for the medical community.
