Brain development is the most rapid during pregnancy and early neonatal months. While prior research has shown that electrophysiological activity of the brain undergoes changes across infancy to adulthood, the role of gestation duration on electrophysiological activity remains largely unknown.This cross-sectional study used data from 73 neonates (postnatal age 1–5 days, 40 females) and 56 toddlers (postnatal age 2.9–3.2 years, 28 females). EEG power spectra were parameterized using Fitting Oscillations and One-Over-F (FOOOF). Multilevel models were employed to neonates, considering different data acquisitions (sleep and auditory paradigm), while only an auditory paradigm was collected from toddlers. We tested the associations between gestational and postnatal ages and FOOOF parameters with maternal educational level, birthweight, and child sex as covariates. We found positive associations between exponent and gestational age both in neonates and toddlers (Figure 1). Also, sex-related differences existed as female neonates had overall higher exponents and offsets compared to male neonates while in toddlers, aperiodic-adjusted alpha center frequencies were smaller in females compared to males. Postnatal age was positively associated with center frequencies in toddlers, while no associations between aperiodic parameters and postnatal age were found in either age group. Our results show, for the first time, that longer gestation duration is associated with aperiodic parameters, suggesting a steeper EEG power spectrum in neonates and toddlers. This suggests that gestation duration may have significant and relatively long-lasting effects on brain physiology. The possible behavioral and cognitive consequences of these changes remain to be elucidated in future research.