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Will my baby be able to breathe?
It's one of the first and most frightening questions parents ask after learning their baby has a congenital lung malformation: will my baby be able to breathe when they’re born? For the vast majority of babies with CPAM, BPS, and other CLMs, the answer is yes. Most babies with congenital lung malformations breathe on their own at birth without any assistance. This guide explains what the research tells us about breathing outcomes and when additional support may be needed.
What the research says
Multiple studies over the past two decades have looked at birth outcomes for babies with prenatally diagnosed lung malformations. The numbers vary depending on the study population and how outcomes are measured, but the overall picture is consistent: the majority of CLM babies are asymptomatic at birth.
Here is what some of the key studies have found:
Kunisaki (2021) — In a narrative review published in Translational Pediatrics, Dr Shaun Kunisaki, a pediatric surgeon and expert on congenital lung malformations at Johns Hopkins, reported that peak CVRs below 0.9–1.0 throughout pregnancy are highly predictive (greater than 90%) of asymptomatic disease at birth. This finding drew on data from the Midwest Pediatric Surgery Consortium, one of the largest multicenter CLM research collaborations in the US.
Cioni et al. (2016) — A single-center retrospective study of 70 prenatally diagnosed pulmonary malformations published in Pediatric Pulmonology found that 63 of 70 fetuses (90%) were asymptomatic at birth and did not require any neonatal resuscitation. Among the 10% who were symptomatic, most had received fetal therapy during pregnancy for complications such as hydrops. The study identified a CVR greater than 1.6 and the presence of fetal complications as predictors of respiratory distress at birth.
Bush and Hogg (2019) — In a review published in Paediatric Respiratory Reviews, the authors noted that most neonates with congenital thoracic malformations (greater than 75%) are asymptomatic at birth, with only a minority requiring any respiratory support.
Peters et al. (2021) — A 2-year follow-up study from Erasmus MC in Rotterdam, published in Ultrasound in Obstetrics & Gynecology, examined prenatal predictors of the need for postnatal respiratory support in fetuses with CLMs. The study confirmed that CVR is a useful predictor and that the majority of prenatally diagnosed CLM babies do not require respiratory intervention at birth.
Midwest Pediatric Surgery Consortium (2017) — In one of the largest multicenter studies to date, the consortium reviewed 506 operatively managed lung malformations across eleven children's hospitals. Of 344 prenatally diagnosed lesions, 134 children (26.7%) had respiratory symptoms at birth. This is a higher number than some other studies because the cohort included only children who ultimately went on to have surgery — it does not include the many babies who were asymptomatic and never required surgical intervention.
Van Schoonhoven et al. (2025) — A recent retrospective cohort from Amsterdam UMC, published in Pediatric Surgery International, reviewed 113 prenatally diagnosed isolated congenital lung anomalies. Of 108 live births, acute respiratory distress was observed in only 6.5% (7 babies). Half of the babies with high-risk CVR values (greater than 1.6) experienced respiratory distress, while distress in the low-risk group was rare and often attributable to other causes.
Pederiva et al. (2023) — The most comprehensive recent overview, published as a Disease Primer in Nature Reviews Disease Primers, confirmed that CLMs occur in approximately 4 out of 10,000 live births and that postnatal presentation ranges from an asymptomatic infant to respiratory failure — but that the vast majority fall on the asymptomatic end of that spectrum.
What does this mean for your baby?
Taking the research together, the best current estimate is that somewhere between 75% and 93% of babies with prenatally diagnosed CLMs are asymptomatic at birth, depending on the study and population. For babies with low CVR values (consistently below 0.9–1.0) throughout pregnancy, that number is even higher at over 90%.
The babies who are most likely to be symptomatic at birth tend to have one or more of the following:
A very high peak CVR (generally above 1.6) during pregnancy
A history of fetal complications such as hydrops, hydrothorax, significant mediastinal shift and/or polyhydramnios in the mother (indicating significant mass effect)
A lesion that has not decreased in size during the third trimester
Congenital lobar emphysema, which has a higher rate of neonatal symptoms compared to CPAM or BPS
Your care team will be tracking these factors throughout your pregnancy. If your baby's lesion is small and stable, with a low CVR, the odds are strongly in your favor.
What does "symptomatic" actually look like?
When we say a baby is "symptomatic at birth," that can mean a range of things: from mild, temporary breathing difficulty (transient tachypnea) that resolves on its own within hours, to more significant respiratory distress that requires breathing support or, in rare cases, emergency surgery. Breathing support also ranges from non-invasive methods like high-flow oxygen and CPAP to intubation for critically sick children.
Not all symptoms are equal, and not all symptomatic babies end up in a serious critical situation. Many symptomatic babies need a short period of monitoring and support and do well. It’s also worth noting that the transition from womb to world is a significant one and it is not uncommon for babies with no lung lesions to also need some breathing support at birth while their lungs transition to breathing room air.
What does "asymptomatic" mean?
An asymptomatic baby is one who breathes on their own at birth without requiring respiratory support. This does not mean the lung malformation is gone or will not necessarily cause problems in the future: it is almost certainly still there. It means it is not causing breathing problems right now. Your baby will still need postnatal imaging and follow-up, and a conversation with a pediatric surgeon about the long-term plan for your child’s specific situation.
A note about CVR
CVR — the CPAM or CLM Volume Ratio — is one of the most important tools your care team has for predicting how your baby will do at birth. It was first developed by Crombleholme et al. in 2002 as a way to normalize the size of a fetal lung mass relative to gestational age. A CVR above 1.6 has consistently been associated with higher risk of fetal hydrops and neonatal respiratory distress. More recently, researchers have been looking at whether lower CVR thresholds (around 1.0–1.25) may also have predictive value for less severe outcomes.
CVR is not the only factor that matters. The type of lesion, the presence or absence of a feeding vessel, whether there has been mediastinal shift, and the overall trajectory of the lesion during pregnancy all play a role.
The bottom line
We know this question keeps you up at night. We know the wait is agonizing. And we know that statistics, no matter how reassuring, don't fully take the fear away because your baby is not a statistic.
But the evidence is clear: the majority of CLM babies breathe on their own at birth. Your medical team is watching your baby closely, and if there are risk factors that change the picture for your specific case, they will talk to you about that. We recommend bringing any questions you have about your specific case to your team and discuss what they expect to happen at birth for your baby. It can also help to discuss different scenarios with them and what the plan will be for each one.
References
Crombleholme TM, et al. Cystic adenomatoid malformation volume ratio predicts outcome in prenatally diagnosed cystic adenomatoid malformation of the lung. J Pediatr Surg. 2002;37(3):331–338.
Cioni R, et al. Pulmonary malformations: predictors of neonatal respiratory distress and early surgery. Pediatr Pulmonol.2016;51(12):1350–1356.
Kunisaki SM. Narrative review of congenital lung lesions. Transl Pediatr. 2021;10(5):1418–1431.
Bush A, Hogg C. Congenital lung malformations: unresolved issues and unanswered questions. Paediatr Respir Rev.2019;29:34–38.
Peters NCJ, et al. Prediction of postnatal outcome in fetuses with congenital lung malformation: 2-year follow-up study. Ultrasound Obstet Gynecol. 2021;58(3):428–438.
Kunisaki SM, et al. Development of a multi-institutional clinical research consortium for pediatric surgery. J Pediatr Surg. 2017;52(7):1148–1155. (Midwest Pediatric Surgery Consortium)
Van Schoonhoven MM, et al. Postnatal outcomes of sonographically suspected isolated congenital lung anomalies. Pediatr Surg Int. 2025;41:155.
Pederiva F, et al. Congenital lung malformations. Nat Rev Dis Primers. 2023;9(1):60.