Behavioral states in the fetus near term

Abstract

On the basis of comparison and analogy it can be stated. that in the mature fetus behavioral states comparable to those seen in the newborn infant, i.e. quiet sleep, active sleep and even some kind of wakefulness do exist (1). These states can be identified fairly well from heart rate and motor activity patterns.According to evaluation of 8 hour recordinqs of FHR and fetal movements in the fetus one complete sleep cycle of quiet sleep plus active sleep lasts about 75 min, duration of one period of quiet sleep is 20 min and duration of one period of active sleep is nearly l hours.Results of Computer analysis of FHR macrofluctuation according to quantification methods developed by the author confirm state related differences of macroflucatuation pattern (2): Macrofluctuation amplitude for 1-min-segments of FHR is in the decile ränge from 3.0 to 7.6 BPM during quiet sleep and from 6.5 to 21.8 BPM during active sleep. Macrofluctuation frequency is in the decile ränge from 3.1 to 6.3 cycles per min during quiet sleep and from 2.1 to 4.9 cycles per min during active sleep.Motor activity of the fetus is unevenly distributed in respect to quiet and active sleep: in 54 % of all periods of quiet sleep no movements were feit by the mothers and in 80 % of all periods of quiet sleep the total number did not exceed 2 movements. Contrary to that in all periods of active sleep except l the total number exceeded 2 movements. On the whole 90 % of motor activity during sleep states occurs during active sleep. Because fetal movement are generally associated with accelerations these data refer to acceleration äs well.These data support the idea that spontaneous changes in centralnervous coordination or state behavior are the predominant causes for spontaneous and distinct changes in FHR and motor activity patterns in fetal wellbeing. In a subsequent investigation fetal ehest movement activity in respect to state behavior was evaluated. According to our results the influence of centralnervous coordination on ehest movement activity is inconsistent: Half of the periods of quiet sleep were without any ehest movements but in the other half ehest movement activity ranged from 10 to 60 % of state duration. Contrary to that in all periods of active sleep ehest movement activity was present, ranging from 5 to 45 % of state duration.From our results it is obvious that for ante partum surveillance of the fetus non stress cardiotocography, fetal heart rate acceleration determination, fetal movement count and evaluation of fetal ehest movement activity cannot be evaluated properly unless fetal state behävior is taken into account.

Maternal Cigarette-Smoking During Pregnancy Disrupts Rhythms in Fetal Heart Rate

“…Spectrum analysis of fetal heart rate showed reliable cycles with a basic rhythm at .3 cpm or its multiples for all but one of the infants. Previous work has indicated that fetuses show cycles in spontaneous movement at these frequencies (Robertson & Dierker, 1986) and that bursts in motor activity are evident in changes in heart rate (Junge & Walter, 1981;Marsal, 1982). Thus, results of this study indicate that the cyclic nature of spontaneous movements may result in comparable cycles in fetal heart rate.…”

“…A lower power of the spectral peak at the frequency of the basic rest activity (1.5 cycles per hour) has been found in newborn infants with atypical fetal growth (Zeskind, Goff, & Marshall, 1991) and other signs of disrupted autonomic regulation (Zeskind, Marshall, & Goff, 1992, 1996. Lower power rhythms averaging .3 cpm have been also found in the spontaneous movement of fetuses of diabetic mothers at 36 weeks' gestation (Robertson & Dierker, 1986), rhythms that should have corresponding changes in fetal heart rate (Junge & Walter, 1981;Marsal, 1982). To the extent that prenatal cigarette exposure disrupts autonomic regulation, we hypothesized that the power of spectral peaks would be reliably lower in infants whose mothers smoked cigarettes during pregnancy.…”

Fetal response to external mechanical stimuli

“…No accelerations are found in the CTG and the oscillation amplitude (macrofluctuations) falls below 10 bpm (narrowing of the band width). We suggest that in order to differentiate between physiological sleep (NREM) and fetal distress with limited compensatory capacity (both lack accelerations, show diminished oscillation amplitudes) one should apply both mechanical stimulation (1-3 χ for 5 seconds each of the head, [1,3,8] [2,6,7,10,11] for an assessment of the fetal CTG is sufficiently taken into account.…”