|Classification and external resources|
An ultrasound featuring a baby with Hydrops fetalis
Hydrops fetalis is a condition in the fetus characterized by an accumulation of fluid, or edema, in at least two fetal compartments. By comparison, hydrops allantois or hydrops amnion are an accumulation of excessive fluid in the allantoic or amniotic space respectively.
Locations can include:
- subcutaneous tissue/scalp
- pleura (pleural effusion)
- pericardium (pericardial effusion)
- abdomen (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 its demand for a 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. The increased demand for cardiac output leads to heart failure, and corresponding edema.
Immune causes 
- Rh disease is a 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. However a small percentage of pregnant mothers are still susceptible to Rh disease even after having been administered anti-D IgG (Rho(D) Immune Globulin)
Non-Immune causes 
The non-immune form of hydrops fetalis has many causes including:
- Iron deficiency anemia
- Paroxysmal supraventricular tachycardia resulting in heart failure
- Deficiency of the enzyme beta-glucuronidase. This enzyme deficiency is the cause of the lysosomal storage disease called Mucopolysaccharidosis Type VII.
- Congenital disorders of glycosylation
- Parvovirus B19 (Fifth Disease) infection of the pregnant woman.
- Cytomegalovirus in mother.
- Maternal syphilis and maternal diabetes mellitus
- α thalassemia can also cause hydrops fetalis when all four of the genetic loci for α globin are deleted or affected by mutation. This is termed Hb Barts (consists of y-4 tetramers).
- Uncommonly, Niemann-Pick Disease Type C (NPC) and Gaucher Disease type 2 can present with hydrops fetalis.
- Turner Syndrome
- Tumors, the most common type of fetal tumor being teratoma, particularly a sacrococcygeal teratoma.
- Twin-twin transfusion syndrome in monochorionic pregnancy (hydrops affects the recipient twin)
- Maternal hyperthyroidism
- fetal cardiac defects and skeletal defects
Hydrops fetalis can be diagnosed and monitored by ultrasound scans. Prenatal ultrasound scanning enables early recognition of hydrops fetalis and has been enhanced with the introduction of MCA Doppler.
|This section requires expansion. (August 2010)|
The treatment depends on the cause.
See also 
- "Hydrops Fetalis: eMedicine Pediatrics: Cardiac Disease and Critical Care Medicine". Retrieved 2010-02-11.
- Equine stud farm medicine and surgery. Retrieved 2010-02-11.
- Isaacs H (January 2008). "Fetal hydrops associated with tumors". Am J Perinatol 25 (1): 43–68. doi:10.1055/s-2007-1004826. PMID 18075961.