Fetal lung mass

Find a fetal care specialist

When an abnormal lung growth affects your baby before birth, figuring out the next steps can feel challenging. The team at our Center for Fetal Care helps you understand your baby’s condition and provides comprehensive care throughout your pregnancy and delivery.

Our fetal surgeons watch for the right time to remove the mass. We have the ability to remove masses even in the uterus (womb). After a safe delivery, a wide range of team members provides all the additional support your newborn may need.

Learn more about what to expect when you come to us for your baby’s care.

What is a fetal lung mass?

Fetal lung masses or lesions are abnormal growths of lung tissue that form in or near the lungs before a baby is born. Masses on lungs are almost always benign (not cancerous), but they can put pressure on the fetus's developing lungs and heart.

In addition to affecting development, a mass on a lung can cause other health problems before and after birth, including:

Hydrops fetalis: If the mass presses on the heart and major blood vessels, the fetus's heart can’t pump blood efficiently. Fluid can then build in their organs, causing the fetus’s belly to swell and excess amniotic fluid to collect in the mother.
Pleural effusion: Large masses on lungs can cause fluid to build up between the lungs and the chest wall.
Neonatal pneumonia: If a fetal lung mass becomes infected, it can lead to pneumonia in newborns and infants.

Types of fetal lung masses

The most common types of fetal lung masses are:

Congenital pulmonary airway malformation (CPAM): The most common fetal lung masses, CPAMs are growths formed from fluid-filled pockets called cysts. The masses contain a few large cysts or many small ones. CPAMs were formerly called congenital cystic adenomatoid malformations (CCAMs).
Bronchopulmonary sequestration (BPS): A BPS is a solid growth that can form inside or outside a lung but isn’t connected to the fetus’s airway. With a blood supply directly from the aorta (largest artery), a BPS can grow quite large.
Hybrid lesion: This lung mass is a combination of a CPAM and a BPS, with features of both types.
Bronchial atresia: Abnormal growths can partially or completely block a bronchus, a section of airway that branches off the trachea (windpipe) into the lungs.

What causes fetal lung mass?

The causes of fetal lung masses are unknown. They aren’t inherited (passed down in families), so they’re not likely to happen again in another pregnancy.

Fetal lung mass symptoms and signs

Usually, fetal lung masses don’t cause noticeable symptoms during pregnancy. Although your baby might show the effects at birth, signs of lung masses sometimes don’t appear for a few months.

Fetal lung mass diagnosis

During a routine ultrasound during pregnancy, doctors can often detect a mass. On lung tissue, any abnormality that shows up on ultrasound requires more detailed imaging to learn about the mass’s size, location and type. If the mass isn’t discovered until after your baby is born, we use the same imaging, which can include:

Ultrafast fetal MRI
Fetal echocardiogram (ultrasound of your baby’s heart)
Additional ultrasounds for ongoing monitoring

We'll also refer you to our genetics program for consultation and evaluation.

Fetal lung mass treatment

Treatment options for fetal lung masses depend on how much they’re affecting the fetus’s heart and lungs. We monitor your baby closely during pregnancy to see if the mass on the lung is growing and watch for any complications. In many cases, fetal lung masses begin to shrink and don’t require treatment until after birth.

If the mass begins to compress the heart or lungs, your baby may need treatment before birth. Treatment options during pregnancy include:

Steroid medications: We prescribe steroids for you that can slow or stop the mass’s growth.
Cyst drainage: We can remove fluid from a CPAM using a needle under ultrasound guidance.
Shunt placement: Along with needle drainage, we place a shunt or catheter (narrow, flexible tube) in the mass. The shunt remains in the mass to continue draining fluid into the amniotic sac (protective membrane surrounding your fetus). We place the shunt through a needle, so no incision is needed.
Fetal surgery: For large masses that are causing hydrops, your fetus may need surgery. Our fetal surgeons perform minimally invasive and open procedures to safely remove fetal lung masses.

EXIT involves providing therapy while your baby is still attached to the placenta. Like a cesarean section, an EXIT procedure is an open surgery, with a hospital recovery of three to four days.

We may treat fetal lung masses and resulting complications by combining EXIT with other procedures, including:

EXIT to airway: We perform a tracheotomy (windpipe incision) to remove a blockage in babies with conditions restricting their airways.
EXIT to ECMO: Extracorporeal membrane oxygenation is a treatment where a machine temporarily takes over lung function for babies who need further treatment. Conditions we treat with this procedure include fetal lung masses, restricted airways and certain heart problems.

If the lung mass is small, your baby might not show any signs or symptoms at birth. Later in childhood, fetal lung masses can become infected or, in rare cases, turn cancerous. For those reasons, we usually plan surgery to remove the mass when your baby is 3 to 12 months old.

We provide ongoing care to prevent lung infections and disease after surgery on a mass on a lung. Our team includes providers from a wide range of specialties, including pulmonology, cardiology, developmental pediatrics, nutrition and social work. We partner with your child’s pediatrician for routine care.