Department of Obstetrics and Gynecology, Clinical Center Novi Sad, Yugoslavia

Definition: Accumulation of fluid in the pleural space. Prenatal pleural effusion may be part of a generalized immune or nonimmune fetal hydrops, accompanying a structural anomaly or, more rarely, an isolated finding. Most primary congenital effusions are chylous and occur on the right[1].

Prevalence: 1:10.000 births (M2:F1)1

Etiology: Pleural effusion may result from either overproduction of lymph or impaired reabsorption1. The etiology of fetal pleural effusions is wide and includes hydrops fetalis of immune and nonimmune origin and over 50 genetic, chromosomal (most often trisomy 21 and monosomy X) and sporadic syndromes, as well as some associated anomalies1^,[2]^,[3]^,[4]^,[5]^,[6].

Possible etiologies of transient pleural effusions may be undetected fetal infection, brief fetal cardiac failure associated with arrhythmias, or transient decreases in fetal colloid osmotic pressure.

Pleural effusions may be1

Unilateral

• Primary
  • most often chylous; often on the right
• Isolated
  • usually associated with an underlying structural anomaly:
    • pulmonary lymphangiectasia
    • cystic adenomatoid malformation of the lung
    • bronchopulmonary sequestration
    • diaphragmatic hernia
    • chest wall hamartoma
    • pulmonary vein atresia

Bilateral

• Secondary
  • Clear; as poart of non-immune hydrops
• Associated with other manifestations of hydrops
  • subcutaneous skin oedema
  • pericardial effusion
  • ascites

Hydrops fetalis, with an incidence of about one per 1,000 pregnancies, is a non‑specific finding in a wide variety of fetal and maternal disorders - haematological, chromosomal, cardiovascular, pulmonary, gastrointestinal, hepatic and metabolic abnormalities, congenital infection, neoplasm and malformations of the placenta or umbilical cord.

Causes of fetal hydrops[7]:

• Heart failure
  • cardiac defects
  • arrhythmias
  • myocarditis
  • fetal anemia
  • arteriovenous shunts
  • mediastinal compression
  • twin/twin transfusion
• Hypoproteinemia
  • Renal defects
  • Gastrointestinal defects
  • Hepatic Infiltratiuons
• Anemia
  • red cell isoimmunisation
  • Parvovirus B19
  • Cytomegalovirus
  • Alpha talassemia
  • Fetomaternal hemorrhage
  • G-6-PD deficiency
• Hepatic Infiltrations
  • Fetal anemia
  • Fetal infection
  • Metabolic disorder
• Arteriovenous shunts
  • vein of Galen aneurysm
  • placental chorioangioma
  • acardiac twin
  • fetal tumor
• Fetal Infection
  • Cytomegalovirus
  • Toxoplasmosis
  • Rubella
  • Syphilis
  • Hepatitis
• Mediastinal compression
  • skeletal dysplasia
  • diaphragmatic hernia
  • cystic adenomatoid malformation of the lung
  • pulmonary sequestration
  • laryngeal obstruction
• Metabolic disorder
  • mucopolysaccharidosis
  • Gaucher’s disease
  • Gangliosidosis
  • Sialidosis
• Neuromuscular disorder
  • fetal akinesia deformation sequence
• Chromosomal disorder
  • Trisomies 21, 18, 13
  • Turner syndrome
  • Triploidy

While in many instances the underlying cause may be determined by detailed ultrasound scanning, frequently the abnormality remains unexplained even after fetal blood sampling or expert post‑mortem examination.

Risk of recurrence: a number of genetic syndromes and chromosomal abnormalities may be accompanied with pleural effusions, and the risk of recurrence depends on the underlying cause.

Teratogens: none1

Ultrasonographic appearances: Chest: fluid surrounds the lung on one (unilateral) or both (bilateral) sides. Amniotic fluid: if polyhydramnios develops, the prognosis is poor.

Pictures 1 and 2 – ultrasound appearances of pleural effusion

Differential diagnosis: The differential diagnosis between the primary pleural effusion causing the fetal hydrops and the secondary one, caused by the hydrops, may be based on the finding on everted diaphragm that occurs in the case of primary effusion.

Associated anomalies: depending on the underlying cause

Prognosis: Irrespective of the underlying cause, infants affected by pleural effusions usually present in the neonatal period with severe, and often fatal, respiratory insufficiency. This is either a direct result of pulmonary compression caused by the effusions, or due to pulmonary hypoplasia secondary to chronic intrathoracic compression. The overall mortality of neonates with pleural effusions is 25%, with a range from 15% in infants with isolated pleural effusions to 95% in those with gross hydrops. Chromosomal abnormalities, mainly trisomy 21, are found in about 5% of fetuses with apparently isolated pleural effusions7.

In humans, isolated fetal pleural effusions may resolve spontaneously antenatally, or persist. In some cases postnatal thoracocentesis may be sufficient but in others the chronic compression of the fetal lungs can result in pulmonary hypoplasia and neonatal death. Additionally, mediastinal compression may lead to the development of fetal hydrops and polyhydramnios, which are associated with a high risk of premature delivery and subsequent perinatal death7.

The major complication of large persistent pleural effusions is prevention of normal lung growth and development, which can result in pulmonary hypoplasia.

Parameters associated with a better prognostic include3:

• later gestational age at diagnosis and delivery

• spontaneous resolution of the effusion prior to delivery

• lack of hydrops

• isolated effusion

• unilateral effusion

Fetal pleural effusions diagnosed in the late second or third trimester with spontaneous resolution have rarely been reported.

Pregnancy management1^,3:

• fetal karyotyping and viral cultures

• maternal serum for TORCH and Parvovirus studies

• fetal echocardiography

• consultation with pediatric surgeon

• 2-3 week ultrasound scans to assess the progress of the effusion

Prenatal therapy:  The main issue in the decision whether the prenatal procedure is to be done is prediction of the development of pulmonary hypoplasia. This is even more difficult in the cases when the massive effusion is detected late and the duration of its existence is not known, therefore the consequences of its existence cannot be predicted. Since all the available prenatal procedures that can be used when the fetus is at risk of developing pulmonary hypoplasia (repeated fetal thoracocentesis, pleuroamniotic shunt, fetal thoracomaternal cutaneous shunting), carry the risks associated with all prenatal surgical procedures (infections, preterm labor, clogging of shunts, etc) and there have been cases of spontaneous resolution of fetal pleural effusions, good clinical judgment and sonographic follow-up are important before embarking on prenatal surgical decompression.

One option in the management of fetuses with pleural effusion is thoracocentesis and drainage of the effusions. However, in the majority of cases the fluid reaccumulates within 24-48 hours requiring repeated procedures and it is therefore preferable to achieve chronic drainage by the insertion of pleural-amniotic shunts^7,[8].

Pleural-amniotic shunting is useful both for diagnosis and therapy7:

• The diagnosis of an underlying cardiac abnormality or other intrathoracic lesion may become apparent only after effective decompression and return of the mediastinum to its normal position

• It may help distinguish between hydrops due to primary accumulation of pleural effusions, in which case the ascites and skin edema will resolve after shunting, and other causes of hydrops such as infection, in which drainage of the effusions does not prevent worsening of the hydrops

• It can reverse fetal hydrops, resolve polyhydramnios and potentially prevent the development of pulmonary hypoplasia.

The outcome of fetuses with isolated effusions after shunting is excellent with survival rates of more than 95%. In hydropic fetuses the survival rate is only 50%, because pleural-amniotic shunting obviously does not cure the underlying disease7.

Technique of pleural-amniotic shunting: Pleural effusions or pulmonary cysts can be drained into the amniotic cavity through a double pigtail silastic catheter (external diameter of 0.2mm). Ultrasound scanning is first carried out to obtain a transverse section of the fetal thorax. With the transducer in one hand, held parallel to the intended course of the cannula, the chosen site of entry on the maternal abdomen is cleaned with antiseptic solution and local anesthetic is infiltrated down to the myometrium. Under ultrasound guidance, a metal cannula with a trocar (external diameter 3mm, length 15cm) is introduced transabdominally into the amniotic cavity and inserted through the fetal chest wall, in the midthoracic region, into the effusion or cyst. The trocar is removed and the catheter inserted into the cannula. A short introducer rod is then used to deposit half of the catheter into the effusion or cyst. Subsequently, the cannula is gradually removed into the amniotic cavity where the other half of the catheter is pushed by a longer introducer. If drainage of the contralateral lung is also needed the appropriate fetal position is achieved by rotation of the fetal body using the tip of the canula. This is an outpatient procedure and after monitoring for 1-2 hrs the patients are allowed home. Subsequently, ultrasound scans are performed at weekly intervals to determine if the effusions reaccumulate, in which case another shunt may be inserted. After delivery the chest drains are immediately clamped and removed to avoid development of pneumothorax[9].

Pictures 3 and 4 - technique of pleural-amniotic shunting

References

[1] Sanders RC. Blackmon LR, Allen Hogge W, Wulfsberg EA. Structural fetal abnormalities – The Total Picture. Mosby. St Lois-Baltimore-Boston, 1996.

[2] Jauniaux E. Diagnosis and management of early non-immune hydrops fetalis. Prenat Diagn 1997 Dec;17(13):1261-8

[3] Parilla BV, Tamura RK, Ginsberg NA.  Association of parvovirus infection with isolated fetal effusions. Am J Perinatol 1997 Jul;14(6):357-8.

[4] Shimizu T, Hashimoto K, Shimizu M, Ozaki M, Murata Y. Bilateral pleural effusion in the first trimester: a predictor of chromosomal abnormality and embryonic death? Am J Obstet Gynecol 1997 Aug;177(2):470-1.

[5] Lau TK, Fung HY, Fung TY. Fetal diaphragmatic hernia presented with transient unilateral pleural effusion.Ultrasound Obstet Gynecol 1997 Feb;9(2):125-7. 

[6] Ibrahim H, Asamoah A, Krouskop RW, Lewis D, Webster P, Pramanik AK. Congenital chylothorax in neonatal thyrotoxicosis. J Perinatol 1999 Jan;19(1):68-71

[7] Pilu G, Nicolaides KH. Pleural effusion. In: Pilu G, Nicolaides KH, Eds. Diagnosis of fetal abnormalities – The 18-23 week scan. Parthenon Publishing 1999.

[8] Ahmad FK, Sherman SJ, Hagglund KH, Johnson MP, Krivchenia E. Isolated unilateral fetal pleural effusion: the role of sonographic surveillance and in utero therapy. Fetal Diagn Ther 1996 Nov-Dec;11(6):383-9.

[9] Nicolaides KH. Personal communications.