Lung malformations: predicting respiratory distress at birth

ABSTRACT
A number of classifications and nomenclatures have been suggested for lung malformations based on the heterogeneous appearances of these abormalities, and “congenital thoracic malformation” has been recommended as an umbrella term for the whole spectrum of developmental lung and thoracic abnormalities. With the implementation and improvement of prenatal ultrasound examinations it appears that the incidence of lung malformations has risen over the last decades. In developed countries, the vast majority of lung malformations are detected in prenatal screening programmes.
Clinical features of lung malformations vary widely. The majority of fetuses have a good outcome, with typically less than 20% of neonates presenting with early life manifestations including neonatal respiratory distress and respiratory insufficiency. Respiratory distress at birth is predicted by size, not the type of a lung malformation. Studies on the natural history of prenatally detected lung malformations have shown that many lesions decrease in size over time; even full prenatal regression of malformations has been described.
A number of variables have been investigated as potential predictors of neonatal respiratory distress and early surgery. The most extensively studied parameter is the congenital pulmonary airway malformation (CPAM) volume ratio (CVR), which represents a volumetric index of mass size allowing for comparisons of fetuses at different gestational ages. In addition, other ultrasound and magnetic resonance imaging (MRI) derived measurements such as maximal (cyst) volume, mass to thorax ratio, observed to expected normal fetal lung volume, fetal cardiac axis, and cardiac position have been investigated. CVR has been associated with the development of hydrops, neonatal respiratory distress in both term and preterm infants, and the need for respiratory support within 24 hours after birth. While consensus on a cut-off value is lacking, it appears that a CVR at presentation of <0.40 is associated with favourable outcomes. However, a low CVR does not completely rule out respiratory problems after birth.
A multidisciplinary approach to the management of fetuses and infants with lung malformations is important, and fetuses at risk should be delivered at specialized tertiary care centers with a neonatal intensive care unit and paediatric surgical expertise to ensure optimal clinical outcomes.

IMPACT STATEMENT
A congenital pulmonary airway malformation volume ratio (CVR) at presentation of <0.40 has been associated with favourable outcomes.

Received: Sept 18, 2024
Accepted: Sept 23, 2024