Context: Apnea in term newborns affects one in 1000 newborns in the US. In spite of this significant prevalence, the condition remains little studied. A pilot study carried out in our center, including 33 full-term newborns presenting with sleep apnea syndrome (SAS), reported that 33% were idiopathic. The objective of this study was thus to determine the epidemiological, clinical and paraclinical characteristics of idiopathic apnea in newborns and infants under 6 months of age, born at term.

Methodology: We conducted a national, observational, retrospective, multicenter study, collecting the different cases of idiopathic apnea in newborns and infants less than 6 months, born at term between 2014 and 2021 as retrieved from the French Reference Centers for rare pediatric lung diseases. Idiopathic apnea was defined by abnormal polysomnography, with an apnea hypopnea index (AHI) ? 1/h, and with no observed etiology except GERD.

Result: 46 newborns and infants younger than 6 months were included at 6 centers. The median (interquartile range [IQR]) age of onset of symptoms was 10 [7;25] days. Cyanosis and hypotonia were the two most described symptoms. These SASs had the following polysomnographic characteristics: a median AHI of 19.4/h [8.27;32.9], a median obstructive apnea index (OAI) of 0.1/h [0;2.7], and a median central apnea index (CAI) of 6.3/h [1.9;12.8].Evolution was favorable in all cases, with regression of the symptomatology and normalization of the AHI at 4 months.

Conclusion: Idiopathic apneas, mostly central SAS, showed a consistantly favorable evolution. A definition of pathological and severe AHI, CAI and OAI thresholds adapted to this age group would, however, seem necessary.