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CPAM Parent Guide
Medically reviewed and edited by Marisa Schwab, MD pediatric surgeon at Lucile Packard Children's Hospital at Stanford
Written by Emily Lake, PhD parent of a child with a CLM diagnosis
Last updated 09/18/2025
What is CPAM?
The cause of CPAM is unknown and nothing you did or didn’t do in pregnancy caused it.
CPAM is a benign (non-cancerous) mass of lung tissue, normally affecting just one lung lobe. CPAM (you may see it called CCAM in older textbooks) is a type of congenital lung lesion (CLM) or malformation. It is not a cancer or a tumor. The mass develops in the lungs very early during pregnancy, sometime before the 10th week of gestation. The CPAM mass can be cystic (fluid- or air-filled spaces), solid, or spongy. The lung tissue that is affected doesn’t work normally, but the rest of the lung—and the other lung lobes—usually develop and function well. Most CPAMs will shrink before birth and the majority of babies are asymptomatic, meaning they have no breathing problems before and after delivery. If surgeons recommend that the CPAM and affected lung lobe be removed after birth, the healthy lung tissue will expand to fill the space. The vast majority of kids will have no long-term impacts on their health or activity levels.
Are there different types of CPAM?
Imaging before birth gives doctors an idea of what the lesion looks like, but it won’t be until a CT scan is done after birth that they’ll have a good idea of whether this is a CPAM or a different type of congenital lung lesion. It will also give a better idea of the location and characteristics of the CPAM.
You might see references online to CPAM “types” also referred to as the Stocker classification. We don’t include these on CPAMparents.org as doctors who treat and study lung malformations are increasingly not using them. This system was not great at reflecting postnatal diagnosis (when a pathologist looks at the CPAM after surgery) and is not commonly used to make medical decisions. Instead, a better classification is whether the lesion appears to be microcystic (or solid) vs macrocystic on an ultrasound.
How rare is it?
Congenital lung malformations, including CPAMs, are uncommon. Estimates for all lesions are 1 in 2,500 live births. CPAM is the most common congenital lung malformation. Currently, approximately 70% of babies with CLM are diagnosed before birth.
Is there a risk of cancer?
A very small number of patients with CPAM develop cancer, but researchers don’t know if the CPAM was actually mistaken for a rare cancer called Pleuropulmonary blastoma (PPB) or whether the CPAM turned into a cancer. More research is needed to truly understand the relationship between CPAM and cancer.
A sketch of the lungs with a CPAM mass (shaded) in the lower left lobe.
A CPAM lesion viewed on an ultrasound. The lesion appears brighter than the surrounding healthy lung tissue. Jordan (2016) Sonographic Appearance of Congenital Pulmonary Airway Malformations
Most CPAMs will shrink before birth and the majority of babies are asymptomatic, meaning they have no breathing problems after delivery.
What happens during a CPAM pregnancy?
Your pregnancy will be more closely monitored than an uncomplicated or lower risk pregnancy. Your medical team will look at the size and appearance of the CPAM and track its growth over time. You will be asked to come in for ultrasounds more frequently. Depending on the size of the CPAM, this could be weekly or every couple of weeks. In rarer high-risk cases, you might have to come in twice a week. Sometimes a fetal MRI may be carried out during the pregnancy to get a more detailed picture of the CPAM, although this is not offered everywhere or for every case. Where the heart is pushed or compressed by the CPAM, a fetal echocardiogram may be requested by your medical team to get a more detailed look at blood flow and how the heart is functioning. Ultrasounds can normally be carried out where you were already receiving prenatal care. You will need to go to a specialist hospital for more specialist imaging if it is requested, like a fetal MRI and fetal echocardiogram.
Who will be involved in my care?
Many different specialists will now be involved in you and your baby’s care. Depending on where you’re receiving prenatal care, you will be connected to a maternal-fetal medicine (MFM) specialist. This is a doctor who works with pregnant women and unborn babies during high risk and complicated pregnancies. The MFM should understand CPAM and will make sure you and your baby are properly cared for. A radiologist will take specialized images of your unborn baby during ultrasounds and interpret these findings. They will be looking for how large the CPAM is and whether it shows any characteristics that might change the course of management and treatment, such as whether it appears to be made up of one lesion or many smaller lesions, and whether these appear to be cystic (filled with fluid or air) or solid. They will also closely look for any signs that the CPAM might be pushing on other organs, such as shifting the heart to the other side of your baby’s chest (mediastinal shift). Doctors will also look for hydrops, which is when fluid builds up in a body’s tissues or organs (such as the lungs, heart, or belly). Closer to the third trimester you will then likely have a consultation with a pediatric surgeon to understand if they plan to operate, when this would be, and what an operation would look like. You may also ask for a consultation with a neonatologist (the specialist doctors who work in NICUs) to understand what will happen at birth if your baby is symptomatic.
What are the risks during pregnancy?
The risks depend on the size, type, and other findings on imaging (such as mediastinal shift and hydrops). Most lung malformations increase in size between 20 and 26 weeks gestation, and then will stay the same or decrease in size.
The CVR Number
The most common way to measure the size of the lesion is the CPAM Volume Ratio (CVR), which estimates the CPAM size in relation to the baby’s head. This gives doctors an idea of how large the CPAM is and, therefore, whether there is a risk of hydrops. In general, a CVR of less than 1.6 is considered lower-risk, while a CVR of greater than 1.6 should lead to increased monitoring because of the higher chance of developing hydrops. The vast majority of CPAM babies without hydrops do very well.
In some countries, doctors will tell you the CVR number at each appointment. In others, they won’t share this information. Some parents find it useful to know and track the CVR while others find that it adds too much stress. Remember that the CVR is an estimate and not 100% accurate. The CVR will change depending on the baby’s position that day, where the cursor took the measurement from, and who the ultrasound tech was. Because these are often very small numbers, a millimeter one way or the other can make a big difference to the CVR.
If your doctor has not shared the CVR number with you, you can calculate it below if you have the measurements of your baby’s CPAM (length, height, width) and the head circumference.
CVR Calculator
Calculates CVR = (Length × Height × Width × 0.52) ÷ Head Circumference. For informational/educational use only.
High risk cases
Higher risk cases are uncommon. If a baby’s CPAM is very large (greater than a CVR of 1.6) they will be watched very closely for signs of hydrops or other fetal distress. Hydrops can be dangerous for both mother and baby, so your doctors will watch you very closely. Depending on the size and change of the CPAM, your doctors may recommend a treatment during pregnancy.
Maternal steroids (betamethasone) may help shrink microcystic/solid CPAMs and can prevent or reverse hydrops in some cases. You may be given multiple doses of steroids.
Thoracoamniotic shunt (a tiny drain placed through the baby’s chest wall into a large fluid-filled cyst) can shrink the size of macrocystic CPAMs.
Fetal surgery and EXIT procedures are rarely considered and carry significant risks.
Higher risk cases are uncommon. If a baby’s CPAM is very large (greater than a CVR of 1.6) they will be watched very closely for signs of hydrops or other fetal distress.
What to expect after birth
Your doctors will talk to you about what they expect for your baby, based on your prenatal imaging. Most babies with CPAM are asymptomatic: they breathe normally at birth and need only routine care. If your prenatal imaging has been reassuring, your team may let you deliver at the hospital of your choice and evaluate your baby in the clinic. Other patients with higher risk need to deliver at a hospital with a NICU, in case your baby needs medical care after delivery. How your baby looks after delivery will determine if the baby goes to the NICU or can be with you in your room.
All babies get a chest x-ray a few hours after birth, even if they’re breathing normally. The chest x-ray often looks normal without a visible lung malformation, even though it’s still there. If your baby doesn’t have any symptoms, the next step after you go home will be a CT scan of the chest (usually when they’re a few months old) and a visit with the pediatric surgeon. The CT scan is important because it shows the location and detailed characteristics of your baby’s CPAM. The surgeon will talk to you about whether they recommend surgery, and what that looks like.
If your baby has symptoms, which happens in about 10% of cases, they may need surgery shortly after birth. The surgeons and neonatologists will talk to you about the details of surgery.
Management and treatment
There are two main paths for CPAM management and treatment. Which one you choose depends on the specifics of your baby’s CPAM, the advice of your medical team, where in the world you are located, and what you feel is best for your child.
Elective surgical removal (most often a thoracoscopic or open lobectomy) in later infancy— normally around 3–6 months—even if a child has no symptoms. This is the common treatment path in the USA and means that the surgeon will remove the entire affected lung lobe. The reason this is recommended by most doctors in the USA is to prevent repeated and severe infections (such as pneumonia) for the rest of the patient’s life, make the diagnosis certain, and address the very small risk of cancer.
The recovery time depends on whether the operation is done via the open or minimally invasive technique. After a thoracoscopic lobectomy, babies usually recover quickly and spend one or two days in the hospital. The remaining lung will expand and grow to compensate for the removed lobe, and most children will have the same lung function as someone who didn’t have lung surgery as a baby. They’ll be able to do all the activities and sports they want when they grow up.Careful observation (“watchful waiting”) with scheduled check-ins and regular imaging. This is the common treatment path for patients with asymptomatic CPAMs in Canada, Australia, and many European countries. If symptoms develop—recurrent chest infections, wheezing not explained by common causes, or a spontaneous pneumothorax—surgery is then usually recommended.
For the majority of babies without hydrops during pregnancy, survival is near 100% and long-term outcomes are excellent. Even for larger CPAMs, modern prenatal monitoring and the use of steroids or shunts have improved outcomes. After birth, surgical removal is considered curative.
There are two main paths for CPAM management and treatment. Which one you choose depends on the specifics of your baby’s CPAM, the advice of your medical team, where in the world you are located, and what you feel is best for your child.