Transient tachypnea of the newborn (TTN) was the name given by Mary Ellen Avery in 1966 to describe a similar clinical presentation in a group of 8 neonates with: marked tachypnea on the first day of life (80–140 breaths/minute), mild cyanosis, mild work of breathing, no evidence of infection, similar chest x-ray findings, and resolution by 2 to 5 days.1 It was also known as type II respiratory distress in the early years in an effort to differentiate it from the better-known respiratory distress syndrome (RDS). It is the most common cause of respiratory distress in the term infant and a frequent reason for admission to the neonatal intensive care unit (NICU).2,3 TTN results from a failure of the normal transition from placental gas exchange in utero to pulmonary gas exchange and breathing. The primary mechanism causing TTN is delayed resorption of fetal lung fluid, a complex process that is now understood to begin several days before spontaneous delivery.4,5 Although our understanding of the processes involved in the clearance of fetal lung fluid has increased, the clinical picture has remained much the same as described in 1966 (Table 24-1).
Table 24-1Key Diagnostic Features of Transient Tachypnea of the Newborn |Favorite Table|Download (.pdf) Table 24-1 Key Diagnostic Features of Transient Tachypnea of the Newborn
|Tachypnea with respiratory rate > 60 breaths/minute, often > 100 breaths/minute |
|Typical chest x-ray findings (hyperinflation, increased perihilar markings, diffuse mild opacities, residual pleural fluid in the interlobar fissures) |
|Hypoxemia and increased work of breathing (usually mild) |
|No evidence of systemic illness or infection |
|Onset in the first few hours of life and lasting more than 6 hours |
|Complete resolution usually by 72 hours, always by 7 days |
Transient tachypnea of the newborn is the most common cause of respiratory distress in the full-term neonate (37–41 weeks) and is responsible for almost half (42.7%–50.3%) of NICU admissions for respiratory distress at term, with an overall incidence of 4.3 to 5.7/1000 live births.6,7 The majority of affected infants are admitted to NICUs for 48 to 72 hours and receive therapies that include respiratory support, intravenous fluids, and antibiotics, resulting in a substantial health care burden. Incidence in premature infants and those with risk factors is substantially higher but often underreported because of overlap with other respiratory disorders associated with prematurity.
Multiple studies have shown that the risk of all types of respiratory distress, and of TTN specifically, increases with each week less than 39 weeks’ gestation.6,8,9 The Consortium on Safe Labor evaluated respiratory outcomes at delivery in 233,844 infants with gestational age greater than 34 weeks, with a special focus on late-preterm infants (34 to 36 and 6/7 weeks) and found the incidence of TTN was highest ...