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What is fetal pleural effusion?

Fetal pleural effusion is the buildup of fluid in a fetus' chest, which can press on the lungs, heart, and main blood vessels. If left untreated, fetal pleural effusion can cause heart and lung problems and can lead to fetal hydrops (accumulation of fluid in a fetus' tissues and organs). Fetal pleural effusion can also lead to excess amniotic fluid, premature birth, stillbirth, and a condition called mirror syndrome, which is the buildup of fluid in a fetus as well as high blood pressure (preeclampsia) in the pregnant person. This endangers the life of both the pregnant person and the fetus.

Fetal Pleural Effusion | Symptoms & Causes

What are the symptoms of fetal pleural effusion?

In most cases, fetal pleural effusion during pregnancy doesn’t cause symptoms in the pregnant person. Fetal pleural effusion is usually diagnosed through fetal imaging such as ultrasound. However, a pregnant person may notice decreased fetal movement, increased belly size due to excess amniotic fluid (polyhydramnios), or swelling due to mirror syndrome.

What causes fetal pleural effusion?

Fetal pleural effusion is a condition where fluid builds up in the space around the lungs of a developing fetus. This can be caused by genetics, heart problems, infections, or anemia. Primary fetal pleural effusion is when there’s no obvious cause for the fluid buildup; it’s rare, happening in about 1 out of 15,000 pregnancies. In this case, the fluid is usually made up of lymphatic fluid that has collected abnormally because of problems with the lymphatic system.

Fetal Pleural Effusion | Diagnosis & Treatments

How is fetal pleural effusion diagnosed?

An ultrasound can usually detect pleural effusion in fetuses. Primary fetal hydrothorax is usually diagnosed when other possible causes, such as structural, genetic, infectious, or anemia, have been ruled out. An ultrasound can also show abnormal positioning of the heart and whether effusion has taken place on one side or both sides of the chest cavity (unilateral or bilateral pleural effusion). Additional tests may be necessary, including:

How is fetal pleural effusion treated?

How we manage fetal pleural effusion depends on the severity of the effusion. Observation is the initial approach in most cases, but fetal intervention may be considered if the effusion progresses, cardiac function is compromised, or other complications arise. These may include abnormal Doppler flow measurements, severe polyhydramnios (excess amniotic fluid), or fetal hydrops.

Prenatal treatment options for fetal pleural effusion:

  • Thoracentesis: An ultrasound-guided needle aspiration of the pleural effusion to either evaluate the fluid content and recurrence or to alleviate the pressure in the chest.
  • Thoracoamniotic shunting: A needle-based procedure in which a small tube is placed connecting the pleural space with the amniotic space. This allows passive drainage of the pleural effusion into the amniotic cavity.
  • Amnioreduction: Drainage of excessive amniotic fluid that has caused the uterus to be overdistended and increased the risk for preterm contractions and labor.

What is the long-term outlook for fetal pleural effusion?

The outlook for a fetus with a fetal pleural effusion depends on how serious their condition is (mild, moderate, or severe) and how far it has progressed. Babies with isolated idiopathic pleural effusion diagnosed before birth usually have a good outcome. They may need to stay in the NICU for a while and face some challenges, and they might need additional interventions. But most babies recover well.

How we care for fetal pleural effusion

The Boston Children’s Hospital Maternal Fetal Care Center is making tremendous progress in better understanding and treating fetal pleural effusion and other fetal health conditions. Our work is a collaboration among fetal surgeons, maternal-fetal medicine specialists, cardiologists, neonatologists, radiologists, genetic specialists, researchers, and other care providers.

Fetal Pleural Effusion | Programs & Services