What are fetal cystic lung lesions?

Fetal cystic lung lesions are a rare condition in which masses or bubbles develop in the lungs of unborn babies. Fetal cystic lung lesions are a congenital condition (a condition that is present at birth).

What are the different types of fetal cystic lung lesions?

The 3 most common types of fetal cystic lung lesions are:

  • Congenital pulmonary airway malformation (CPAM). A CPAM is a condition that causes a cystic mass (fluid-filled bubbles) of abnormal (unusual) lung tissues to develop in unborn babies. CPAMs usually grow in the lower lobe (portion) of the lungs. They do not have a blood supply (blood vessels that grow in and/or around the mass). Between 18-26 weeks gestation, CPAMs usually grow in size and change in shape. After 26 weeks, many CPAMs slow in growth, shrink or stop growing.
  • Bronchopulmonary sequestration (BPS). Unlike CPAMs, BPS are areas of abnormal lung tissue that have their own blood supply but are not connected to the airway. They can form within the lung tissue (intralobar) or outside of the lung tissue (extralobar). They can also change size during gestation, and a few disappear all together.
  • Hybrid lesions. These lesions have parts or qualities of both CPAMs and BPS.

What causes fetal lung lesions?

The causes of fetal lung lesions are unknown. Many fetal lung lesions happen at random. It is not a hereditary condition (passed down in families). About 1 out of every 25,000 unborn babies develop a fetal lung lesion.

Do fetal lung lesions affect the mother during pregnancy or after birth?

Usually, fetal lung lesions do not cause serious problems for the mother during pregnancy. The mother will receive frequent fetal ultrasounds to check how the lesion is growing and for any signs of hydrops (a rare, but serious condition that causes a build-up of fluid in your baby’s body).

What is hydrops?

A fetal lung lesion only becomes a problem if affects the position of your baby’s heart or the flow of blood and/or fluid within the lungs. This can lead to a rare, but serious condition called hydrops (similar to heart failure in adults). This causes a build-up of fluid in your baby’s skin, chest and abdomen and can be life-threatening. Hydrops only occurs in about 1 out of every 10 babies who have fetal lung lesions.

In most babies, fetal lung lesions do not grow big enough to be dangerous for your baby. If your baby does show signs of hydrops, your maternal fetal medicine doctor will discuss further imaging and treatment options.

Rev. 8/2021. MassGeneral Hospital for Children and Massachusetts General Hospital do not endorse any of the brands listed on this handout. This handout is intended to provide health information so that you can be better informed. It is not a substitute for medical advice and should not be used to treatment of any medical conditions.