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Fourier analysis was applied to episodes of high and low heart-rate variation in the near-term fetus. The spectral densities of the variations in pulse intervals from 1 to 7 cycles/min, were almost identical with those found by De Haan et al. (1977) in the newborn infant during both active and quiet sleep. A computer programme, designed to separate low and high heart-rate variation episodes in the fetus, identified seven of the eight quiet sleep episodes in four infants. None of the other neonatal behavioural states had low heart-rate variation. It was concluded that, with other published data, there is increasing, although indirect, evidence that low heart-rate variation episodes indicate quiet sleep in the human fetus near term.

Original publication




Journal article


British journal of obstetrics and gynaecology

Publication Date





50 - 55


Fetal Heart, Humans, Electrocardiography, Sleep, Pregnancy, Heart Rate, Fourier Analysis, Infant, Newborn, Female