CDH represents a malformative disorder characterized by an incomplete diaphragm formation. This results in poor lung development (pulmonary hypoplasia), associated with altered vascularization of the lung (pulmonary hypertension), determining respiratory and cardiovascular insufficiency at birth. CDH shows high mortality and significant morbidity so that its prognostic evaluation remains challenging.

The measurement of lung area at chest radiography is considered an alternative method to assess lung development in the newborn. A correlation between lung area and functional residual capacity (FRC) was demonstrated in newborns with CDH.

However, the relationship between lung area and other aspects of respiratory function has never been investigated. Since CDH compromises lung development as a whole, it is likely to assume that lung area at birth may have an impact on patient's performance at pulmonary function tests during follow-up. In particular, as lung area increased, a trend towards normalization in respiratory function would be expected.

Moreover, the role of the radiographic area at birth as a possible predictor of death should be further characterized, aiming to clarify the complex association between lung area and mortality, which is strongly influenced by both pulmonary hypoplasia and pulmonary hypertension.

The principal aim of this study is to determine if changes in the radiographic pulmonary area measured on the first day of life are related to patients' pulmonary function at one year of life, considering two main respiratory parameters: tidal volume (VT) and respiratory rate (RR).

Secondary objectives are the analysis of the association between radiographic pulmonary area and: 1) risk of death during the first year of life; 2) risk of hernia recurrence during the first year of life.

The investigators will retrospectively consider a cohort of newborns with CDH. For each patient, the investigators will measure lung area at chest radiography performed preoperatively within 24 hours after birth and will collect data regarding demographics, clinical course, and follow-up.

Through our study, the investigators aim to improve the current understanding of the role of radiographic lung area in characterizing lung development and prognosis in CDH patients. The investigators believe that this could become a low-cost and straightforward tool that will assist the clinician in making decisions regarding the patient's management and follow up.

The study period considered will be January 2012 - December 2018. From the medical record of each patient, the investigators will collect the following data: prenatal history, hernia severity, fetal endoscopic tracheal occlusion (FETO) procedure, demographics, respiratory insufficiency, and mechanical ventilation, cardiocirculatory insufficiency and pharmacological hemodynamic support, pulmonary hypertension and need for pulmonary vasodilators, need for extracorporeal life support (ECMO), comorbidities, timing of surgical repair, use of prosthetic patch, intra- and post-operative complications, clinical and instrumental follow-up, pulmonary function tests, recurrence, death. The confidentiality of all data will be maintained.

Regarding the assessment of the radiographic pulmonary area, two operators (a neonatologist and a pediatric radiologist) will independently review all preoperative digital radiograms performed within 24 hours of life. For each patient, the radiogram showing the best lung-recruitment will be selected. Lung area will be assessed by freehand tracing of the perimeter of the thoracic area, as outlined by the diaphragm and the rib cage, excluding the mediastinal structures and abdominal contents herniated in the thorax. The only aerated portion of the lungs will be considered. The corresponding area will be automatically calculated by the software. Three measures will be performed: 1) ipsilateral lung area (cm2); 2) contralateral lung area (cm2); 3) total lung area (cm2), derived from the sum of the preceding two. The agreement between lung measurements performed by the two operators will be evaluated to verify the reproducibility of the method.

Pulmonary function test performed during spontaneous sleeping at the age of 1 year will be reviewed. The measurements of VT and RR will be recorded. The predicted value of VT and RR will be obtained, and their Z-Score will be calculated using reference equations of a population of healthy children. Z-Score is a numerical measure used to express how much an observed value deviates from the mean expected normal value in terms of standard deviation.

Inclusion Criteria:

• Inborn and outborn patients admitted to the NICU within 24 hours after birth.
• Prenatal or postnatal (within 24 hours after birth) diagnosis of CDH.
• Preoperative chest radiograph performed for clinical purposes within 24 hours after birth in our NICU.

Exclusion Criteria:

• Diagnosis of CDH made beyond 24 hours after birth
• Admission to the NICU beyond 24 hours after birth
• Preoperative chest radiograph performed beyond 24 hours after birth, rotated/asymmetric, with air leak (pneumothorax, pneumoperitoneum), not performed in our NICU or not accessible
• Early death (within 1 hour after birth)

Infants with CDH born between January 2012 and December 2018, hospitalized at birth or within 24 hours of life at the Neonatal Intensive Care Unit of Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy, and followed-up longitudinally during the first year of life.