Congenital bronchial atresia (CBA) Parent Guide

What is Congenital Bronchial Atresia?

The cause of congenital bronchial atresia is unknown and nothing you did or didn’t do in pregnancy caused it. 

Congenital bronchial atresia (CBA) is a rare congenital lung malformation (CLM) where a segment of the airway (bronchus) didn’t grow normally. This happens very early during pregnancy, sometime before the 10th week of gestation. The result is that a small area of lung cannot communicate properly with the rest of the airways. Because air can’t move in and out normally, that area of lung may become over-inflated. On imaging, it may appear as a bright, cystic or air-filled area.

CBA can affect one small segment or an entire lung lobe. It most commonly affects the upper lobes, but it can occur in any part of the lung. 

How rare is it? 

Congenital lung malformations, including CBAs, are uncommon. Estimates for all lesions are 1 in 2,500 live births. CBA is rarer than CPAM and BPS, although it is commonly found as a “hybrid lesion”, meaning for example that CBA and CPAM are both present in the lung tissue. Currently, approximately 70% of babies with a CLM are diagnosed before birth.

Is there a risk of cancer?

There is no known pathway for a CBA to develop into cancer. There may be an increased risk of cancer with CPAM, and some patients have hybrid lesions, meaning both CBA and CPAM. More research is needed to truly understand the relationship between CPAM and cancer.

What happens during a bronchial atresia pregnancy?

Like other CLMs, bronchial atresia is usually detected on a prenatal ultrasound, often when a bright area of the lung is seen. There may be signs that the lesion is pushing on other organs, such as shifting the heart to the other side of your baby’s chest (mediastinal shift). There is also possible flattening of the diaphragm on the side affected by the CBA lesion. Importantly, the CBA will be connected to the pulmonary system and have a normal blood supply. This indicates it is not another type of congenital lung malformation called a sequestration. However, it can be difficult to distinguish CBA from CPAM before birth because these lesions can look very similar on prenatal imaging. An accurate diagnosis is usually made only after surgical evaluation. 

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 lung lesion and track its growth over time. You will be asked to come in for ultrasounds more frequently. Depending on the size of the CBA, this could be weekly or every couple of weeks. Sometimes a fetal MRI may be carried out during the pregnancy to get a more detailed picture of the lung lesion, although this is not offered everywhere or for every case. Where the heart is pushed or compressed by the CBA lesion, 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 lung malformations 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 lung lesion is and whether it shows any characteristics that might change the course of management and treatment. They will closely look for any signs that the CBA 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), although this is much rarer in CBA cases than in higher risk CPAM or BPS. 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 a lung lesion’s size in relation to the baby’s head. This gives doctors an idea of how large the lesion 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 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 lung lesion (length, height, width) and the head circumference.  

High risk cases

Higher risk cases are very uncommon with bronchial atresia. If a baby’s lung lesion is very large (greater than a CVR of 1.6) they will be watched 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. Most cases of bronchial atresia are stable or improve as the pregnancy progresses. Intervention during pregnancy (such as steroids or fetal surgery) is rarely needed for CBA, since these lesions usually don’t cause serious complications before birth.

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 bronchial atresia are born at term and are asymptomatic, meaning they breathe normally at birth and do not need breathing support, 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 a higher risk case may 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 bronchial atresia. 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 congenital lung malformations, 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 bronchial atresia management and treatment. Which one you choose depends on the specifics of your baby’s lung lesion, 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 and make the diagnosis certain.
  
  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 CBA 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. 

Bronchial atresia is one of the rarest congenital lung malformations, but it is also one of the least likely to cause serious problems. While it may look dramatic on prenatal imaging, most babies with CBA do extremely well. For the majority of babies without hydrops during pregnancy, survival is near 100% and long-term outcomes are excellent. With careful monitoring, the right specialists, and clear communication, families should feel confident that their baby’s prognosis is excellent.