What constitutes a “normal” background electroencephalography (EEG) rhythm immediately after birth is not well understood. We performed video-electroencephalography recordings in the first six hours (first measure) and the third day of life (second measure) for evidence of transient changes in brain function.

We performed a cohort study of an incidental sample of healthy term neonates in a single-center nursery. Main outcome measures were as follows: (1) EEG visual analysis, which included sleep-wake cycles, proportions of discontinuity and bursts with delta brushes, and number per hour of alpha/theta rolandic activity, encoches frontales, and transients; and (2) the electroencephalographic spectral analysis, which included power spectrum in the following frequency bands: delta, 0.5 to 4 Hz; theta, 4 to 8 Hz; alpha, 8 to 13 Hz; and beta, 13 to 30 Hz. Theta/delta and alpha/delta ratios were also calculated.

Twenty-two babies were enrolled. Significant findings (P < 0.05) in the first six hours with respect to 48 to 72 hours of life were (1) increased discontinuity, indeterminate sleep, and bursts with delta brushes; (2) higher number of transients, and lower number of alpha/theta rolandic activity and encoches frontales. Minimal changes were found in power spectrum data. However, using receiver operating characteristic curve analysis, theta/delta ratio ≤0.484 was the best cutoff to discriminate between the two measures (positive predictive value, 100.0; 95% confidence interval 71.0 to 100).

In healthy term neonates, immature electroencephalographic patterns, lack of clearly defined sleep-wake cycles, and frequent transients can be considered normal electroencephalographic findings in the first six hours of life. Normative power spectrum data are provided. These findings suggest that neonatal adaptation immediately after birth leads to transient changes in brain function.