OBJECTIVE: This preliminary study investigated electrophysiological and microstructural features of sleep in children and adolescents 4-18 years of age who were born to depressed mothers. METHODS: A total of 31 healthy subjects (15 male and 16 female) participated in the study. In this sample, 20 children born to mothers diagnosed with Major Depressive Disorder (MDD) were designated as "high-risk"; 11 children born to mothers without a personal history of depression were designated as "low-risk." Polysomnography including three-channel electroencephalography (EEG) was recorded for one night at the Pediatric Sleep Unit of the University Hospital of Lyon, France. Clinical and demographic data were collected. Sleep architectural parameters were analyzed. Sleep microstructure was assessed with the scoring of cyclic alternating pattern (CAP) and CAP measures were calculated. Spectral analysis was performed, and mean EEG band power was computed for each sleep stage. Sleep electrophysiological features (slow waves and sleep spindles) were detected, and related parameters were analyzed. Data were compared between high- and low-risk groups using Student t tests. RESULTS: A reduction in low-frequency spindle activity and slow spindles spatio-temporal characteristics over frontal and central derivations, and an altered distribution of CAP phase A subtypes (reduction of A1 over A2-3 ratio) were observed in the high-risk group relative to the low-risk group. CONCLUSION: Limited spindles generation and increased non-rapid eye movement sleep instability, observed in children born to depressed mothers, might reflect functional anomalies in cortical plasticity that could represent a pathogenic factor or an epiphenomenon for MDD.