Is Transient Tachypnea of the Newborn a Risk Factor for Bronchiolitis in the First Two Years of Life? A Population-Based Birth Cohort Study.

Objective: Transient Tachypnea of the Newborn (TTN) is a common cause of respiratory distress in term infants, associated with delayed pulmonary fluid clearance resulting from dysfunction of the epithelial sodium channel. Although generally self-limiting, TTN may increase early childhood wheezing and asthma risk. This study aimed to assess the incidence and characteristics of acute bronchiolitis in TTN infants compared to those in healthy controls within a large birth cohort.

Methods: We conducted a population-based cohort study that included all live births in Istanbul from January 2016 to December 2018, utilizing the Turkish Ministry of Health's e-Nabız database. Infants diagnosed with isolated TTN (International Classification of Diseases [ICD]-10 P22.1) formed the study group. A randomly selected control group of healthy infants without respiratory diagnoses was included in the study. Both groups were followed for two years to identify episodes of acute bronchiolitis (ICD-10 J21*), excluding cases within the first month of life. The data collected included bronchiolitis incidence, recurrence, age at the time of the episode, and hospitalizations.

Results: Among 1,002,261 live births, 14,389 TTN infants and 14,500 controls were analyzed. Acute bronchiolitis occurred in 42.4% of TTN infants and 35.8% of controls (p<0.001). TTN infants had higher rates of single episodes, while controls experienced more recurrent episodes (p<0.001). Hospitalization was more frequent in the control group (p<0.001), with single hospitalizations predominating in the TTN group and multiple hospitalizations in the control group. The first episodes in TTN infants mainly occurred between 1-6 months, with controls showing more episodes early but fewer later (p<0.001). Recurrence was correlated with an earlier age of the first episode in both groups (p<0.001).

Conclusions: TTN infants experience more bronchiolitis episodes early in life, though recurrent episodes are more common among healthy controls. Further studies are warranted to investigate the relationship between TTN and the development of wheezing and asthma.