Pericardial effusion in the fetus

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1. Introduction to the structure and role of the pericardium

The pericardium is a fibrous, enveloped sac that contains the heart and the base of the great vessels. The pericardium is actually composed of two layers: parietal (outer) and visceral (inner).
The role of the pericardium is to prevent sudden expansion of the heart (especially the right chamber) and sharp displacement of the heart and major blood vessels. The very thin layer of physiological fluid in the pericardial cavity helps to minimize the friction force of the heart with surrounding structures during each stroke, while the pericardial layer is also responsible for helping to prevent the spread of infection or cells. cancer cells from the lung and pleura.

2. What is fetal pericardial effusion?

Fetal echocardiography finding less than 2 mm of pericardial fluid is a frequent finding, occurring in about 40–50% of normal fetuses. This feature is most easily detected when the ultrasound beam is perpendicular to the ventricular wall. This finding has no clinical significance and is not considered a pericardial effusion.
Fetal pericardial effusion is identified on ultrasound examination if the heart is partially or completely enclosed by fluid visible in all views, usually present around the atrioventricular groove. Simultaneously, the thickness of the fluid layer should be more than 2 mm and cross the atrioventricular fissure.
If the thickness of the fluid is less than 4 mm, it is considered a small pericardial effusion; Conversely, from more than 4 mm, it is classified as a large pericardial effusion. The main differential diagnosis of fetal pericardial effusion is pleural effusion. This finding also frequently shows up on ultrasound as a layer of fluid surrounding the lungs.

3. Causes of pericardial effusion in the fetus

Fetal pericardial effusion can be found as a single manifestation or in combination with various abnormalities in the heart as well as in other organs. The incidence is about 0.64–2.00%. Therefore, when fetal echocardiography detects pericardial effusion, the fetus should be performed comprehensively to rule out various causes related to this effusion.
In most cases, pericardial effusion occurs as a manifestation of fetal edema, due to immunological or non-immune mechanisms. However, this assessment must rule out the possibility of fetal pericardial effusion secondary to inflammation, infection, malignancy, or autoimmune disease.
Accordingly, common pathologies associated with fetal pericardial effusion are as follows:
Fetal heart rhythm disturbances; Congenital heart defects ; Fetal heart tumors, such as fetal pericardial teratomas; Increased incidence of chromosomal abnormalities, such as trisomy 21; Fetal infection; Parvovirus infection, CMV, HIV

4. Treatment methods when detecting pericardial effusion in the fetus

When a pericardial effusion is detected in the fetus, the doctor will need to do a full ultrasound evaluation of the fetus and blood tests of the mother to determine the presence of abnormal antibody groups. This is done non-invasively through the mother's venous blood draw. However, in cases where a high probability of abnormality is suspected, an indication for amniocentesis for sampling and umbilical cord blood sampling should be made. If no cause is found, the fetal pericardial effusion is considered to be transient and idiopathic. These cases have a good prognosis and nearly 45% of cases will resolve spontaneously by the time the baby is born.
For cases of high-output heart failure secondary to fetal ischemia, arrhythmia, or congenital heart disease, the mother and fetus should perform in-depth studies for differential diagnosis. In cases of fetal anemia, pericardial effusion is an early sign of edema, which should be treated early to limit the risk of stillbirth.
In the case of cardiac teratomas, the pericardial effusion may result from tumor irritation of the pericardial layers and rupture of cystic areas in the pericardium due to the polycystic nature of the pericardial tumour. Furthermore, the tumor may cause mechanical obstruction to venous and thoracic return, impede lymphatic drainage, and lead to progression of pericardial, pleural effusion, ascites, and pleural effusion. fetal body. Esophageal compression can cause polyhydramnios. At this time, pericardial effusion and space-occupying effect are the cause of fetal cardiac tamponade.
However, fetal pericardial effusion is rarely associated with cases of malignancy. Several cases of rhabdomyolysis with pericardial effusion have been described in the literature due to rapidly growing muscle mass and onset of arrhythmia patterns. There have been rare cases of fetal pericardial effusion associated with cardiac fibroids and hemangiomas. A small number of cases of pericardial effusion involve cardiac diverticulum, which is thought to be caused by rubbing of the sac mesh with the pericardial wall.
In summary, fetal pericardial effusion occurs when there is excessive accumulation of fluid in the pericardial cavity of the fetus remaining in the uterus. To be considered abnormal, the pericardial fluid thickness must be greater than 2 mm. These cases need to be carried out more in-depth investigations to find the cause and timely treatment, ensuring a safe pregnancy. If no abnormalities are found, fetal pericardial effusion can fortunately be considered idiopathic and resolve spontaneously until the baby is born.
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