Transient tachypnea of the newborn (TTN, TTNB, or "transitory tachypnea of newborn") is a respiratory problem that can be seen in the newborn shortly after delivery. Amongst causes of respiratory distress in term neonates, it is the most common. It consists of a period of rapid breathing (higher than the normal range of 40-60 times per minute). It is likely due to retained lung fluid, and is most often seen in 35+ week gestation babies who are delivered by caesarian section without labor. Usually, this condition resolves over 24–48 hours. Treatment is supportive and may include supplemental oxygen and antibiotics. The chest X-Ray shows hyperinflation of the lungs including prominent pulmonary vascular markings, flattening of the diaphragm, and fluid in the horizontal fissure of the right lung.
Due to the higher incidence of TTN in newborns delivered by caesarean section, it has been postulated that TTN could result from a delayed absorption of fetal lung fluid from the pulmonary lymphatic system. The increased fluid in the lungs leads to increased airway resistance and reduced lung compliance. It is thought this could be from lower levels of circulating catecholamines after a caesarean section, which are believed to be necessary to alter the function of the ENaC channel to absorb excess fluid from the lungs.
Pulmonary immaturity has also been proposed as a causative factor. Levels of phosphatidylglycerol (an indicator of lung maturity) were found to be negative in certain newborns.
Mild surfactant deficiency has also been suggested as a causative factor.
TTN is a diagnosis of exclusion as it is a benign condition that can have symptoms and signs similar to more serious conditions, such as respiratory distress syndrome. A chest X-ray may show a radiopaque line - fluid - in the horizontal fissure of the right lung, fluid infiltrate throughout alveoli or fluid in individual lung lobes.