Hydrops fetalis

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Overview
Hydrops fetalis is a condition in the fetus characterized by an accumulation of fluid, or edema, in at least two fetal compartments, including the subcutaneous tissue, pleura, pericardium, or in the abdomen, which is also known as ascites. The edema is usually seen in the fetal subcutaneous tissue, sometimes leading to spontaneous abortion. It is a prenatal form of heart failure, in which the heart is unable to satisfy demand for an unusually high amount of blood flow.

Classification and causes
Hydrops fetalis usually stems from fetal anemia, when the heart needs to pump a much greater volume of blood to deliver the same amount of oxygen. This anemia can have either an immune or non-immune cause. Non-immune hydrops can also be unrelated to anemia, for example if a tumor or congenital cystic adenomatoid malformation increases the demand for blood flow.

Immune causes

Rh disease is the major cause for immune mediated hydrops fetalis; however, owing to preventative methods developed in the 1970s Rh disease has markedly declined. Rh disease can be prevented by administration of anti-D IgG (Rho(D) Immune Globulin) injections to RhD-negative mothers during pregnancy and/or within 72 hours of the delivery.

Non-Immune causes

The non-immune form of hydrops fetalis has many causes including:
 * Iron deficiency anemia
 * Deficiency of the enzyme beta-glucuronidase. This enzyme deficiency is the cause of the lysosomal storage disease called Mucopolysaccharidosis Type VII.
 * Parvovirus B19 infection of the pregnant woman.
 * α thalassemia can also cause hydrops fetalis when all four of the genetic loci for α globin are deleted or affected by mutation.
 * Uncommonly, Niemann-Pick Disease Type C (NPC) can present with hydrops fetalis.
 * Turner Syndrome
 * Rarely, a tumor. The most common type of fetal tumor is a teratoma, particularly a sacrococcygeal teratoma.

Diagnosis
Hydrops fetalis can be diagnosed and monitored by ultrasound scans.

Treatment
The treatment depends on the cause.

Severely anemic fetuses can be treated with blood transfusions while still in the womb.