What is fetal pleural effusion?

Fetal pleural effusion (or hydrothorax) is an accumulation of fluid in the chest cavity of a developing fetus. As the fluid increases, it can compress the developing lungs and heart. There are many different underlying causes of pleural effusion in a fetus. Causes can include genetic issues, infection, and underlying heart or lung conditions.

The outlook for a fetus with a pleural effusion depends on how the amount of fluid that is in the chest. A very high amount of fluid trapped in the chest can lead to fetal heart failure (hydrops) and underdeveloped lungs (pulmonary hypoplasia) which can result in a poor outlook for the baby at birth.

Diagnosis

Diagnosis of pleural effusion is made by ultrasound. If it is discovered on a routine scan you will be referred to the fetal medicine unit for further investigation and managment.

The fetal medicine doctor will perform a detailed ultrasound scan and may offer you the following investigations:

-MRI to assess the fetal chest in more detail;

-Amniocentesis (needle test) to check the genetic make-up of the fetus, these studies to rule out chromosomal abnormalities that would affect the baby’s survival or long-term outcome;

-Blood tests to rule out certain causes of hydrothorax such as fetal infection;

-Fetal echocardiology – specialised heart scan of the fetus.

The fetal medicine team and multidisciplinary team will review imaging and test results, discuss the diagnosis, explain treatment options and potential outcomes, and answer any questions you may have.

Treatment options for pleural effusion

Depending on the diagnosis, fetal intervention may be an option for treating pleural effusion.

Thoracentesis (fluid drainage)

If fluid accumulates in the fetal chest and is severely compressing the fetal heart and lungs, the fetal medicine doctors at St Michael’s Hospital in Bristol can perform a thoracentesis, a procedure performed under continuous ultrasound guidance in which we use a small needle to drain the fluid.

Draining the fluid relieves the pressure on the baby’s heart and lungs. The fluid will be tested to determine its origin – this helps us identify the cause of the fluid buildup and guide treatment. The fluid is also tested for infection and chromosomal abnormalities.

In some cases the fluid may reaccumulate 24 to 72 hours after the procedure. If this occurs, a thoracoamniotic shunt can be placed for continuous fluid drainage.

Fetal thoracoamniotic shunt

A shunt is a hollow tube that provides a passageway for the excess fluid to go from the fetal chest cavity through the chest wall to the amniotic fluid space around the fetus. The mother receives antibiotics before the procedure.

Under ultrasound guidance, a trocar (hollow needle) is guided through the mother’s abdomen and uterus and then inserted through the fetus’s chest wall to remain in place until delivery.

A mother can be discharged the same day of shunt placement and return to the fetal medicine unit one week later to ensure the shunt is functioning properly. 

Effective fluid drainage via thoracentesis or thoracoamniotic shunt placement leads to a decrease in fluid volume. This helps to improve lung growth, resolves hydrops, and improves long-term survival rates.

More information can be found here.

Delivery of babies with fetal pleural effusion

Mothers carrying babies with a thoracoamniotic shunt would need to deliver in a hospital with access to a neonatal team skilled in managing the shunt at delivery. Mothers carrying a baby with a small pleural effusion that is not causing any lung or heart complications may be able to deliver in their local hospital with a neonatal review following birth.