Study Objectives: Fetal growth restriction (FGR) occurs in up to 10% of pregnancies and is associated with increased risk of prematurity and neurodevelopmental impairment. FGR also alters sleep-state distribution in utero and maturation in infancy. Currently, limited data on the long-term associations of FGR and childhood sleep exist. Accordingly, we assessed the associations between preterm birth and FGR and sleep in children aged 5-12 years.Methods: Seventeen children born preterm and FGR, 15 children born preterm but appropriately grown (appropriate birth weight for gestational age [AGA]), and 20 term AGA children (controls) were studied using overnight polysomnography. Sleep macroarchitecture was assessed using standard criteria, and sleep microarchitecture was assessed using spectral analysis of the electroencephalogram (C4-M1) with total, δ (0.5-3.9 Hz), θ (4.0-7.9Hz), α (8.0-11.9 Hz), σ (12.0-13.9 Hz), and β power (14.0-30 Hz) calculated.Results: For sleep macroarchitecture, preterm FGR children had higher N2% compared with term AGA children (p < .05). Preterm AGA children had reduced total sleep time, NREM%, and sleep efficiency compared with term AGA children (p < .05 for all). For sleep microarchitecture, preterm FGR children had a higher amount of total, δ and α power compared with both groups (p < .05). Sigma and β power was lowest in the preterm AGA group compared with both groups (p < .05 for both).Conclusions: Prematurity and FGR were associated with altered sleep macro-and microarchitecture measures indicative of reduced sleep quantity and quality in childhood. As sleep disturbance can affect both behavior and neurodevelopment in children, sleep in FGR and preterm children warrants further investigation. Keywords: fetal growth restriction, preterm birth, pediatric, EEG spectral analysis, sleep. Statement of SignificanceFetal growth restriction (FGR) is a major obstetric complication affecting up to 10% of pregnancies leading to increased risk of preterm birth and neurodevelopmental impairment. FGR alters the development of sleep in fetal life and infancy; however, few studies have investigated the long-term impact on sleep. This novel study assessed both sleep macro-and microarchitecture in children born preterm and FGR. Being born preterm and FGR was associated with reduced sleep quality, whereas being born preterm with an appropriate birth weight for gestational age was associated with both reduced sleep quantity and quality. This study highlights the potential need for clinical follow-up of sleep and investigation of the effects of poor sleep on neurodevelopment in this population.