Background: Animal studies indicate that postnatal adaptation and development of neonates could be different due to the birth method and that these effects may last throughout adulthood. Study design: We applied a spatio-temporal analysis to EEG recordings of a group of neonates to investigate the influence of a cesarean section on maturation and extrauterine adaptation of the brain. EEG were recorded at 2 h and at 24 h after delivery. Subjects: A spectral analysis technique, the so-called Karhunen-Loeve (KL) method, was applied to EEG of 10 neonates from vaginal delivery and 17 from C-section to obtain the spatio-temporal eigenpatterns. Results: Spatio-temporal analysis showed noticeable pattern differences between the two groups. Compared to the C-section, the vaginal delivered neonate's EEG recordings showed a significant increase of amplitude at Fpl in the pattern 24 h after the delivery, but not 2 h after delivery. Dynamics in this spectral analyses were not significantly different between both groups 2 h after delivery, but the regional differences increased during the next day between both groups. Conclusions: This could come from the early insufficient complexity in C-section neonates. Global EEG complexity in C-section neonates fell short of that of vaginal delivered neonates 2 h after delivery. Many aspects of pattern change in C-section neonates followed the nature of vaginal delivered neonates. These could be considered as parts of a retarded transition of C-section neonates in the early adaptation, but some of the differences in global EEG pattern could not be explained in this way. Pattern analysis suggests that the neuronal activities of the neonatal brain are changing regionally concurrent with bi-hemispheric global dynamics. Moreover, the delivery modes could have an influence on the early postneonatal adaptation of the physiological activity in brain. (C) 2003 Elsevier Ireland Ltd. All rights reserved.