Partial spectral element in the chronome of a human neonatal heart rate at term.

An initial infradian prominence characterizes the spectral element of the chronome or the time structure of half-hourly heart rates during the first 40 days after birth of a boy born at term. Immediately pertinent infradian prominence, which was previously documented for many premature infants and anticipated from the integration of 2-day segments of half-hourly data from infants born at term, is now displayed longitudinally. Dominating first are an about-weekly (circaseptan) or half-weekly (circasemiseptan) and an about 26-day (circatrigintan) component, with a subsequent change from infradian to circadian prominence.