Temporal structure of body core temperature in twin newborns

On the basis of our previous investigations on rectal temperature in newborns, we studied the rhythmic variations of body core temperature in twins immediately after birth. We studied 8 pairs of healthy full-term twins during the first two days of life. Continuous recording of body temperature was performed every 10 minutes for 24-48 hours by a solid memory recorder (Fiamarker) connected with a disposable rectal probe. Data were analysed by the single cosinor method and spectral analysis. All the newborns, except one, demonstrated a statistically significant circadian periodicity of body temperature (p<0,001). Acrophases were distributed along the 24 h immediately after birth since the synchronization to the new environment of life was not yet completed. The spectral analysis of data demonstrated ultradian fluctuations of temperature in 14 of the newborns. Temperature data in newborn twins should be collected over a time span long enough to allow discrimination between the adaptation phase and the beginning of the synchronized span.