[A spectral analysis of the periodic components in the heart rhythm structure of newborn infants].

Spectral analysis of spontaneous heart rate fluctuations were assessed in 12 healthy newborn infants and in 14 low birth weight newborns. The orthostatic test was performed by the change of newborns posture. High-frequency fluctuations at the respiratory rate were detected in healthy infants and orthostatic reactions of heart rate resembled the same reactions in healthy adults.