Pneumothorax originating in the perinatal period

**Definition:** Abnormal presence of air or other gas in the pleural cavity, usually secondary to tracking of free air from pulmonary interstitial emphysema, or rupture of subpleural blebs.

**Long definition:** Abnormal presence of air or other gas in the pleural cavity, usually secondary to tracking of free air from pulmonary interstitial emphysema, or rupture of subpleural blebs that can be associated with mediastinal shift with kinking of the great vessels and impaired cardiac output