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Pleural effusion - accumulation of fluid in the chest cavity Pericardial effusion - accumulation of fluid around the heart Peritoneal effusion - accumulation of fluid in the abdominal cavity Diffuse edema (fluid in the pleurae, peritoneum and/or around or under the fetus's skin).


Pleural effusion is an accumulation of fluid between the lungs and the external wall of the chest cavity. This fluid can contain:
  • In most cases, lymphatic fluid - this type is known as a chylothorax.

  • Watery fluid (clear, serous and noninflammatory) - this is a hydrothorax.

  • Blood - this is a hemothorax. This type is very rare and usually only occurs in adults.

Pericardial effusion only is a relatively rare intrauterine condition. If there is a pericardial effusion, its quantity is usually small and insignificant and the condition is usually transient. The pericardial effusion, if present, is usually part of a general condition of edema (clear, serous fluid) of the pleurae and peritoneum, which can affect the rest of the body as well at a later stage.

Peritoneal effusion only is also rare in the fetus. Here too, most of the fluid in the abdominal cavity is or will be part of a general condition of edema involving the pleurae and possibly becoming more widespread later. Diffuse edema (ana sacra) is an extreme example of this condition. Fluid accumulates in the subcutaneous (under the skin) tissues of the fetus and is usually accompanied by an accumulation of clear, serous fluid in the pleurae, peritoneum and pericardium.

Clinical signs

In chylothorax, the fluid is milky and contains a high concentration of lipids (triglycerides), proteins and white blood cells (lymphocytes).

As long as the newborn has not eaten, for a short time after birth the fluid drained from the chest cavity can appear clear in spite of containing these substances.

In half of these cases there is a spontaneous recovery over time, but until this happens, the fluid must be continuously drained through a tube inserted into the chest cavity.

Treatment in these cases is supportive.
There have already been successes in inserting a drain, which contains a one-way valve, into the fetus in utero, allowing for normal development of the lungs on the side of the effusion.

The cause is usually not known, but these effusions can be associated with certain chromosome disorders such as Turner syndrome or Down syndrome, etc., and chromosome analysis should be performed. Effusions can also be associated with heart defects, intrauterine infection and other defects - tests for these should also be carried out as they may indicate the presence of a genetic syndrome.

Where there is watery (serous) fluid in the chest cavity and/or abdominal cavity and/or diffuse edema, this is due to the accumulation of this fluid in many parts of the body, starting with the chest cavity and progressing to the abdominal cavity and subcutaneous tissues. This situation is known as diffuse edema. There are many causes:
  1. Severe fetal anemia. This can be caused by:
    • Blood group incompatibility of various types. Hemolytic anemia, which involves destruction of the red blood corpuscles, can be identified in the fetus by the presence of maternal antibodies that pass through the placenta into the fetal bloodstream. These antibodies can be demonstrated in a blood test performed on the mother's blood, known as Coombs' test, and in this situation the result in the mother will be positive. In order to identify the exact type of incompatibility, it is important to examine other parameters as well, such as the mother's and fetus's blood groups (ABO and rhesus), and also the blood subtypes. Treatment involves a blood transfusion into the fetus by injection into the fetus's abdominal cavity, and this can be repeated if necessary. After birth, neonatologists care for the infant and if necessary will give a blood transfusion in order to prevent jaundice of the newborn. In the past, the main cause of fetal edema was rhesus incompatibility. Nowadays rhesus negative women are given injections after the delivery of every baby and after every miscarriage in order to prevent the development of anti-rhesus antibodies in the mother. These antibodies, when present in the mother's blood and when they enter the fetus's bloodstream via the placenta, destroy the fetus's blood cells. Because all rhesus negative women are now treated, it is very rare nowadays for a fetus to be affected by rhesus incompatibility problems, and therefore nowadays most diffuse edemas are not due to severe fetal anemia.

    • Viral infection by a parvovirus. This condition usually resolves without causing defects. It can be demonstrated in the maternal bloodstream by testing for antibodies to this virus.

  2. Heart defects.

  3. Threatened abortion.

  4. Non-parvovirus intrauterine infection.

  5. Many diseases, such as various metabolic disorders.

  6. Various genetic syndromes such as Noonan syndrome, etc.

Inheritance pattern

Depends on the type. Most problems are not hereditary.


Not known

Associated features that can be demonstrated in tests performed during pregnancy

In these cases, chromosome disorders such as Turner syndrome and Down syndrome, etc., heart defects, intrauterine infection (including parvovirus) and other defects that may indicate the presence of a genetic syndrome must be looked for. Chromosome analysis and fetal echocardiography should be carried out as well as ultrasound examination. Blood group incompatibility must also be investigated.

In all these cases it is important to refer the couple for genetic counseling, to which they should bring all data, including the results of other tests performed during the pregnancy such as alpha-fetoprotein, nuchal translucency, etc.

In the case of chylothorax only, the prognosis is usually good, and the condition usually resolves after drainage and supportive therapy after birth. Conversely, in the case of serous edema and diffuse edema, even if the results of all tests are found to be normal, there is still an increased risk for syndromes that cannot be detected in pregnancy tests. Therefore it is necessary to refer the parents to a multidisciplinary clinic in a hospital for professional counseling by a geneticist, an expert in ultrasound examinations and/or a pediatric cardiologist, and a neonatologist, in order to collate all the data and discuss the various risks in each specific case, the method of monitoring the fetus, possible intervention if indicated, etc. The decisions taken will depend on the severity of the problem, the presence of additional findings, etc.

What is the risk of recurrence in a subsequent pregnancy?

This depends on the cause. Most cases are not hereditary. The exact risk for recurrence is determined within genetic counseling based on the cause of the edema, the pedigree, the results of tests such as chromosome analysis, etc.

Molecular genetic information

The gene for the disease

Depends on the cause/type

Its location

Depends on the cause/type

Genetic testing

Diagnostic testing

Depends on the cause/type

Carrier testing

Depends on the cause/type

Fetal testing

Depends on the cause/type
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