The COllaborative Neonatal Network for the First CPAM Trial

Inclusion Criteria: * Lesion detected during routine prenatal ultrasound screening * Delivery at term: gestational age ≥37 weeks * Birthweight \> -2SD or \>P10 * Asymptomatic at birth defined as no prolonged respiratory distress or oxygen support (\< 24 hours) * Asymptomatic up to the moment of inclusion * Confirmation of CPAM on postnatal chest CT-scan at 3-9 months of age, according to structured report form (34) * Unilateral lesion occupying no more than one lung lobe as assessed on chest CT-scan at 3-9 months of age Exclusion Criteria: * Bilateral lesion * Development of symptoms before randomization, considered by treating physician as caused by CPAM with reasonable certainty * Complicated pregnancy defined as (pre-)eclampsia, pregnancy diabetes in mother, foetal hydrops or severe polyhydramnios on prenatal ultrasound * Syndrome associated anomalies on genetic analysis confirmed by genetic expert * Major associated malformations. Anomalies include cardiac malformations requiring surgical correction or follow-up by a paediatric cardiologist, congenital malformations requiring major surgical intervention, and anomalies that affect normal lung growth and development. * Suspicion of malignancy on chest CT scan evaluation at the age of 3-9 months * Participation in another randomised controlled trial