The blood flow velocity waveform in the fetal descending aorta: its relationship to fetal behavioural states in normal pregnancy at 37-38 weeks

In 13 normal pregnancies, the relationship between the blood flow velocity waveform at the lower thoracic level of the fetal descending aorta and fetal behavioural states at 37-38 weeks of gestation was studied. The pulsatility index (PI), as a measure of peripheral vascular resistance, was significantly lower during state 2F compared to state 1F according to the classification by Nijhuis et al. (Nijhuis, J.G. et al. (1982) Early Hum. Dev., 6, 177-195), suggesting an increased perfusion of the fetal skeletal musculature to meet the energy demand needed for the raised muscular activity during state 2F; A significant inverse relationship (P less than 0.001) was established between PI and FHR in state 2F; this was mainly determined by a significant rise in end-diastolic flow velocity (P less than 0.02). Both the behavioural state and FHR should be taken into account when evaluating flow velocity waveforms in the fetal descending aorta during the latter weeks of pregnancy.     

Behavioural states in growth-retarded human fetuses

Behavioural state observations were carried out on 12 fetuses which subsequently had birthweights below the 10th percentile. Their gestational ages at the time of study ranged from 32 to 40 weeks. Real-time ultrasound scanning was used to detect fetal body and eye movements, and the fetal heart rate was continuously recorded using a clinical fetal monitor. None of these fetuses was severely acidemic or depressed at birth. Findings in the growth-retarded fetuses were compared with those obtained in the fetuses of 14 low risk nulliparae and 14 low risk multiparae by means of the same techniques (van Vliet et al. (1985) Early Hum. Dev., 12, 121-135.; Nijhuis et al. (1982) Early Hum. Dev., 6, 177-195). The appearance of states seemed to be delayed in the growth-retarded fetuses. States were present in only three of eight growth-retarded fetuses studied at 40 weeks, whereas only one of 16 low risk fetuses did not show states at this age. Also at 40 weeks, the proportion of discordant association of the state variables was increased in the growth-retarded fetuses in comparison to the low risk group. There were no consistent differences between the two groups in the occurrence of defined combinations of parameters of the state variables at earlier ages. The growth-retarded fetuses showed differences in the quality and quantity of somatic motility in comparison to low risk fetuses of equivalent gestational age. These observations suggest that some aspects of central nervous system function are disturbed in growth-retarded fetuses, even in the absence of fetal distress.     

The relationship between the response to external light stimulation and behavioral states in the human fetus: how it differs from vibroacoustic stimulation

OBJECTIVE: To determine the effects of external light stimulation on fetal behavioral states and know the difference from those of vibroacoustic stimulation. METHODS: A flashlight and a vibroacoustic stimulator was applied directly on the maternal abdomen to determine the response of 56 normal fetuses at 36-40 weeks gestation. Fetal heart rate (FHR) and body movements were recorded using an actocardiograph, and fetal eye movements were observed using real-time ultrasonography. Using Nijhuis's criteria, the fetal behavioral states (1F-4F) were determined. FHR acceleration was considered a fetal response to the stimulations. RESULTS: The lag time between stimulation and fetal response was within 4 s. A positive response rate to the light stimulation was higher at behavioral states 2F (82%) and 3F (83%) than at state 1F (4%). Light stimulation changed the behavioral state of two of the six 3F fetuses (33%) from 3F to 4F. No change of state was observed in fetuses that were in states 1F and 2F. For vibroacoustic stimulation, fetal response was 100% positive and changes of states were observed frequently irrespective of the behavioral state before the stimulation. CONCLUSION: Fetal response to light stimulation is closely connected to fetal behavioral states and may reflect some distinct stages of the sleep-wakefulness cycle.     

The blood flow velocity waveform in the fetal descending aorta; its relationship to behavioural states in the growth-retarded fetus at 37-38 weeks of gestation

In 12 patients with intrauterine growth retardation (IUGR), the relationship between the blood flow velocity waveform at the lower thoracic level of the fetal descending aorta and fetal behavioural states at 37-38 wk of gestation was studied. A significant inverse relationship (P less than 0.001) was established between pulsatility index (PI) and fetal heart rate (FHR) in state 1F and 2F. The PI as a measure of peripheral vascular resistance, demonstrated a marked increase compared to normal pregnancy. There is a virtual overlap of PI values originating from state 1F and 2F according to the classification by Nijhuis et al. (J.G. Nijhuis, H.F.R. Prechtl, C.B. Martin, Jr. and R.S.G.M. Bots (1982) Early Hum. Dev. 6, 177-195). The peripheral vasoconstriction present in IUGR seems to overrule state dependent PI fluctuations. The marked rise in PI, particularly at lower FHR and the constancy of PI in relation to fetal behavioural states can be considered vascular adaptations, which are instrumental in the centralization of the fetal circulation, with the aim of favouring blood supply to the brain, heart and adrenals during IUGR.     

Are there behavioural states in the human fetus?

The aim of this study was to search for the existence of behavioural states in the human fetus and to describe their developmental course. In a longitudinal study, 14 low-risk fetuses were studied at 2-week intervals from 32 weeks of gestation onward. Fetal body movements as well as fetal eye movements, visualized by means of real-time ultrasonic imaging, and fetal heart rate patterns, recorded by means of a cardiotocograph, were used as state variables.At 38 and 40 weeks, four distinct behavioural states, named states 1F through 4F and corresponding respectively to states 1 through 4 of the neonate, could be identified. That these constellations of parameters represented true behavioural states was demonstrated by the stability of association of parameters for prolonged periods and by the simultaneity of change of parameters at state transitions. There is evidence for episodes of wakefulness in the fetus. Before 36 weeks, cycles were present in each of the state variables, and combinations of parameters typical of particular states were observed. However, the relatively short durations of these combinations and the lack of simultaneity of change in the three state variables support the conclusion that these periods of coincidence occurred by chance and did not represent organized behavioural states.     

The Doppler flow velocity waveform in the fetal internal carotid artery with respect to fetal behavioural states. A longitudinal study

Doppler flow velocity waveforms in the fetal internal carotid artery were recorded in 21 normal pregnancies during fetal behavioural state IF (quiet sleep) and 2F (active sleep) according to Nijhuis and co-workers, from the 36th week of gestation onwards. The present study confirms the earlier finding of a significant reduction of the pulsatility index (PI) in state 2F as compared to state 1F at 37-38 weeks of gestation and demonstrates that this difference in PI exists throughout the entire period, in which fetal behavioural states have been described. Furthermore, it is demonstrated that there is a significant reduction in PI of this vessel during the last 4 weeks of gestation, suggesting a haemodynamic redistribution, favouring blood supply to the brain during the latter weeks of gestation.     

Vibro-acoustic stimulation of the human fetus: effect on behavioural state organization

Vibro-acoustic stimulation of the human fetus in being increasingly performed both antenatally and during labour, to differentiate between poor and good fetal health in cases of flat or otherwise suspect fetal heart rate patterns. In a controlled study we investigated the effect of the electronic artificial larynx (EAL) on fetal behavioural state organization. In 10 healthy women with normal pregnancies of 38-40 weeks of gestation, recordings of fetal heart rate, body movements and eye movements, with a duration of 120-210 min, were carried out during two consecutive days. In each fetus, 3-4 episodes of state 1F and consecutive state 2F were studied, one of which served as a control observation. EAL stimulation during state 1F was associated with excessive fetal movements and with a state change in 7 out of 9 observations (four times into 2F; three times into 4F). Stimulation during state 2F was associated with a change into 4F in four of the nine observations. On days with EAL stimulation the fetuses spent more time in state 4F or in an episode not classifiable (because of an atypical FHR pattern with tachycardia and small accelerations) than control fetuses (21% vs. 3% of time). Disorganized states or periods of state 4F sometimes lasted for more than 1 h following the stimulation. It is concluded that stimulation with the EAL induces excessive fetal movements, a prolonged tachycardia, non-physiological state changes and a disorganisation and change in the distribution of fetal behavioural states. Until more is known regarding the safety and risks of vibro-acoustic stimulation, it should not be used in a routine clinical setting.     

Behavioural states in the fetuses of nulliparous women

Behavioural state observations were carried out serially on the fetuses of 14 low risk nulliparae. They were observed serially at 2-weekly intervals between 32 weeks gestational age and delivery at term. Two real-time ultrasound B-scanners were used to visualize fetal body, eye and breathing movements. Fetal heart rate patterns were recorded simultaneously by means of a clinical fetal monitor. States appeared to be present transiently in three fetuses at 34 weeks. States were definitely present in five of 13 fetuses studied at 38 weeks and six of seven observed at 40 weeks. In comparison to the fetuses of low risk multiparae studied earlier, the fetuses in the present study showed a somewhat lower proportion of quiescence (coincidence 1F) and higher percentage of activity (coincidence 2F); however, most of these differences were not statistically significant. In the fetuses which showed states, the distribution and durations of the states at 38 and 40 weeks were not different from those found previously in the fetuses of multiparae. We conclude that the development of behavioural states is generally similar in the fetuses of low risk nulliparae and multiparae, but that states appear at a somewhat later gestational age in the fetuses of nulliparae.     

Mild impairment of neuro-otological function in early treated congenital hypothyroidism.

Pure tone audiometry, tympanometry, acoustic stapedial reflex thresholds (ASRTs), and auditory evoked brain stem responses (AEBRs) were carried out in 38 children with early treated congenital hypothyroidism aged 10-12 years, together with tests of vestibular function (electronystagraphy, rotational, and caloric tests). Sensorineural hearing loss with thresholds of greater than 15 dB was detected in 18 children (10 at 8 kHz only); only two children had more than 40 dB hearing loss, each in one ear. Raised ASRTs were found in eight children and two children had abnormal AEBRs. Of the 29 children tested, 12 had an abnormality of vestibular function. Although not significant at the 5% level, there was a tendency for the abnormalities to be more prevalent and severe in the children with more severe hypothyroidism, as judged by pretreatment plasma thyroxine. It is concluded that (i) mild abnormality of hearing is still common in children with congenital hypothyroidism despite early treatment but this is much less severe than that found before neonatal screening and (ii) mild abnormalities of vestibular function may be common in early treated congenital hypothyroidism.     

Mild impairment of neuro-otological function in early treated congenital hypothyroidism

Pure tone audiometry, tympanometry, acoustic stapedial reflex thresholds (ASRTs), and auditory evoked brain stem responses (AEBRs) were carried out in 38 children with early treated congenital hypothyroidism aged 10-12 years, together with tests of vestibular function (electronystagraphy, rotational, and caloric tests). Sensorineural hearing loss with thresholds of greater than 15 dB was detected in 18 children (10 at 8 kHz only); only two children had more than 40 dB hearing loss, each in one ear. Raised ASRTs were found in eight children and two children had abnormal AEBRs. Of the 29 children tested, 12 had an abnormality of vestibular function. Although not significant at the 5% level, there was a tendency for the abnormalities to be more prevalent and severe in the children with more severe hypothyroidism, as judged by pretreatment plasma thyroxine. It is concluded that (i) mild abnormality of hearing is still common in children with congenital hypothyroidism despite early treatment but this is much less severe than that found before neonatal screening and (ii) mild abnormalities of vestibular function may be common in early treated congenital hypothyroidism.     

Are the behavioural states of the newborn comparable to those of the fetus?

Comparisons were made between ultrasound behavioural recordings of 18 healthy term fetuses and recordings of the same variables of the same individuals at 3 to 5 days postnatally. Statistical comparison of the frequency of eye movements, limb and body movements revealed that the fetal states 1F and 2F were comparable to quiet sleep (S1), and rapid eye movement (REM) sleep (S2), respectively in the newborn. Comparisons between the fetal states and wakefulness were less clear-cut. The heart rate in each of the three states in the fetus was about 20 beats per min higher than in the corresponding postnatal state, although the patterns were similar. States 1F and 2F accounted for a higher percentage of the fetal observations (86%) than states S1 and S2 in the neonatal observations (64%), but the ratio of the different types of sleep was similar in both recordings (30% quiet sleep to 70% REM sleep). State S3 (quiet awake) always and only occurred in the postnatal observations in association with feeding. No comparable behaviour occurred during the prenatal observations (2050 min in 18 fetuses). Numerically the movements observed in S5 (crying) were not significantly different from 2F, however qualitatively there were marked differences, and also S5 was characterized by a heart rate pattern quite unlike anything observed prenatally (often with a rate in excess of 200 beats per min). We postulate that S3 and S5 are postnatal behavioural adaptations to extrauterine existence.     

Fetal homologue of infant crying

Four behavioural states are recognised in the human fetus and are comparable to those of the neonate: 1F (quiet sleep), 2F (active state), 3F (quiet awake), and 4F (active awake). State 5, or crying, is not considered to have a fetal correlate. In a study assessing the effects of exposure to tobacco and cocaine during pregnancy on fetal response and habituation to vibroacoustic stimulation, what appears to be the fetal homologue of crying was observed. These behaviours were seen on ultrasound, and have been captured on video recordings and include: an initial exhalation movement associated with mouth opening and tongue depression, followed by a series of three augmented breaths, the last breath ending in an inspiratory pause followed by an expiration and settling. This is the first report/video documenting these behaviours and suggests the possibility of a state 5F.     

Fetal cardiac and motor responses to octave-band noises as a function of central frequency, intensity and heart rate variability

Accelerative and decelerative cardiac responses and motor responses (leg movements) of 37-40 weeks (G.A.) fetuses are analyzed as a function of the frequency of three octave-band noises (respectively centered at 500 Hz, 2000 Hz and 5000 Hz) and of their intensity level (100, 105, 110 dB SPL, ex utero), during high (HV) and low (LV) heart rate (HR) variability pattern states. In both states, increasing the frequency and/or the intensity of the acoustic stimulation: (i) increases the ratios and amplitudes of accelerations, and the motor response ratios, (ii) reduces deceleration ratios and motor response latencies. Cardiac and motor reactiveness are higher in HV than in LV with acceleration ratios always greater than motor ones. However, when a high intensity and/or frequency is used, the reactiveness differences between states disappears. Low intensity and/or frequency stimulation levels induce a majority of decelerations.     

Hearing loss at the age of 5 years of children born preterm–a matter of definition

The effect of three common hearing impairment criteria on the prevalence of hearing loss was evaluated in 58 prospectively followed-up 5-year-old children born preterm at 32 weeks of gestation. Audiological assessment was done as part of an extensive neurodevelopmental evaluation at the age of 5 years. With the criterion based on the classification of the World Health Organization (average threshold hearing level >25dB at frequencies of 0.5, 1 and 2 kHz, classified according to the less impaired side) there were two preterm children with mild hearing impairment. With Clark's criterion (unilateral average threshold hearing level > 15dB at frequencies of 0.5, 1 and 2 kHz) eight children had slight hearing impairment; seven of these had conductive hearing problems. With the criterion of a single frequency-specific deficit > 15 dB for 0.25-4 kHz the number of hearing-impaired children was 28 out of 54 (51.9%), most of whom had conductive or unspecified hearing deficits. Moreover, of the four multiply handicapped, retarded children whose pure tone thresholds were not assessed mon-aurally, three would belong to the hearing-impaired group according to Clark's criterion and four according to the frequency-specific criterion, Hearing impairment, hearing impairment classification, low birthweight, preterm     

Vibroacoustic stimulation in normal term human pregnancy

OBJECTIVE: To examine the effects of vibroacoustic stimulation (VAS) on fetal heart rate (FHR) in term human fetuses by computerized carditocography system. METHODS: FHR was analyzed 20 min before and 30 min after vibroacoustic stimulation using the Oxford Sonicaid System 8002 for computerized FHR measurement. Recordings were made in 31 uncomplicated pregnancies at 36-42 weeks' gestation. RESULTS: Vibroacustic stimulation of the fetus evoked a significant increase in all the parameters evaluated (number of fetal movements, of accelerations above 10 and 15 bpm, in high- and low-variability episodes, and in short-term variations). Concerning the effect of behavioural states on the response to VAS, some changes (FHR, high-variability episodes) occurred independently of behavioural states, while other parameters (accelerations >10 and 15 bpm: short-term variation) underwent statistically significant changes only for behavioural states 1F and 2F. CONCLUSIONS: Our study supports the hypothesis of a significant fetal response in normal term pregnancy, as clearly shown by computerized cardiotocography. The immediate response occurred independently of behavioural states, although some differences were present (mainly for F1 and F2 states) if the evaluation was extended in time.     

The intercostal-to-phrenic inhibitory reflex in the human fetus near term

Human fetal breathing movements (FBM) differ from neonatal breathing in that they are predominantly paradoxical and are not present all the time. Respiratory pauses are common in the fetus while prolonged apneas are life-threatening in the neonate. In the latter they occur during state 2 (active sleep) when paradoxical breathing is more frequent. Then the inward movement of the thoracic wall causes spreading of the caudal ribs which may elicit an intercostal-to-phrenic inhibitory reflex (IPIR) leading to apnea. This is not the case in state 1 (quiet sleep). In the fetus similar sleep states, state 2F and 1F respectively, have been identified and we investigated if the IPIR is already present before birth and if so, if the response is different between 1F and 2F. In 21 healthy fetuses between 37 and 40 weeks, two real time scanners and a cardiotocograph were used to asses the fetal behavioural state. If FBM were present, the caudo-lateral part of the fetal thoracic wall was shortly compressed manually and the period that FBM ceased measured. During the same epoch moments of sham-stimulation, i.e. control periods without actual compression were also carried out. In 15 out of 16 fetuses with FBM in 1F, and in 19 out of 19 fetuses in 2F, compressions were immediately followed by an apnea. In contrast, moments of sham-stimulation never induced apnea, indicating that the IPIR is indeed present in both behavioural states.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hourly fetal urine production rate in the near term fetus: is it really increased during fetal quiet sleep?

Fetal bladder volume and hourly fetal urine production (HFUPR) is calculated on the assumption that the fetal bladder is ellipsoid in shape. A recent validation study demonstrated a progressive overestimation at increasing bladder volumes. This may be due to changes in shape of the fetal bladder at increasing volumes. Two independent papers have shown increased HFUPR during fetal behavioural state 1F (S1F) when compared with S2F. The aim of the present study was to assess whether this increase of HFUPR during S1F, previously observed by others, could be the result of an error introduced by the method of volume calculation. A retrospective evaluation was performed in a series of 208 HFUPR measurements in 123 normal near term pregnant women attending a low-risk antenatal clinic. Adequate bladder filling in both states was identified in 43 recordings. Maximum fetal bladder volumes were greater (>10 ml) during S1F in comparison to S2F in 56% of these recordings and HFUPR was significantly greater during S1F only in these cases. Bladder volumes are usually lower during S2F as a result of fetal voiding, which occurred in association with 22 of 36 transitions from S1F to S2F, and only 1 of 13 transitions from S2F to S1F (P<0.001). When disregarding calculated bladder volumes in excess of 20 ml for the purpose of calculating HFUPR, eleven recordings remained. HFUPR calculated in this way was significantly lower in comparison to measurements where larger bladder volumes were included and no difference was observed between states.

This implies that the differences observed are the result of the greater error in calculating bladder volumes and HFUPR during S1F, where volumes are usually greater and that calculation of fetal bladder volume should not be performed on the assumption that the bladder is ellipsoid in shape. Alternative techniques include limiting measurements to a maximum volume of approximately 20 ml, when the bladder is usually ellipsoid in shape or basing volume calculation on the surface area of a series of sagittal views as suggested by Hedriana and Moore [Hedriana HL, Moore TR. Ultrasonographic evaluation of human fetal urinary flow rate: accuracy of bladder volume estimations. Am J Obstet Gynecol 1994;170:1250–1254; Hedriana HL, Moore TR. Accuracy limits of ultrasonographic estimation of fetal urinary flow rate. Am J Obstet Gynecol 1994;171:989–992.]     

Vibratory acoustic stimulation and the flow velocity waveform in the fetal internal carotid artery

Eleven healthy fetuses between 36 and 39 weeks of gestation were studied during the active sleep state to examine effects of a 5-s vibratory acoustic stimulus on the baseline fetal heart rate and flow velocity waveform in the fetal internal carotid artery. There was an immediate marked rise in baseline fetal heart rate with concomitant drop in pulsatility index in the flow velocity waveform of the fetal internal carotid artery, which persisted for at least 15 min after the stimulus. However, when the pulsatility index was standardized for a fetal heart rate of 140 beats/min this index remained virtually unaltered. These data suggest that in the healthy term fetus during active sleep state, a vibratory acoustic stimulus has no measurable effect on cerebral vascular resistance. Since virtually all reported studies on vibratory acoustic stimulation of the fetus were carried-out during the quiet sleep state, the data from the present study do not provide any information on the safety of this device when employed as a means of assessing of fetal well-being.     

Can spontaneous movements be modulated by visual and acoustic stimulation in 3-month-old infants?

BACKGROUND: The assessment of the quality of general movements (GMs) in infants proves to be a reliable and valid diagnostic tool for detecting brain dysfunction early in life. Of special interest, particularly for the prediction of cerebral palsy, is the fidgety kind of GMs, the so-called fidgety movements (FMs) observable in 3- to 5-month-old infants. GMs are part of an infant's spontaneous motor repertoire and as such endogenously generated by the nervous system itself. AIM: The question was raised as to what extent the temporal organisation of FMs can be modulated by visual and acoustic stimulation. STUDY DESIGN: Spontaneous motility in supine position with and without stimulation was recorded on video and the data were semiquantitatively analysed. We studied the effect of visual stimulation (red ring, red puppet), unanimated acoustic stimulation (68, 77, 88 dB) and of the mother, approaching her infant in a talkative manner after an absence of a quarter of an hour. SUBJECTS: Twenty-nine healthy infants at the age of 12 weeks who all showed normal FMs. RESULTS: Visual stimulation demonstrated that only the presentation of a red puppet elicited a significant level of focussed attention and led to a decrease of FMs. A red ring, unanimated acoustic stimulation as well as the interaction with the mother had no influence on the temporal organisation of FMs. CONCLUSION: This study demonstrated that in 3-month-old infants, FMs is a predominant motor pattern and that it is possible to assess FMs during (playful) social interaction.     

Failure of high intensity auditory stimuli to affect behavioral arousal in children during the first sleep cycle

Behavioral and physiologic indices of arousal to auditory stimuli were examined during the first cycle of sleep in 8-12-year-old hyperactive children and nonhyperactive controls. No behavioral responses or sustained awakenings were obtained for any child during the first cycle of sleep to stimuli at intensities up to 123 dB sound pressure level re 0.0002 dynes/cm2), i.e., at intensities more than 90 dB above waking threshold values. Half of the arousal attempts in stage 2 and a quarter of those in stage 4 elicited a partial or momentary physiologic arousal response (i.e., EEG desynchronization and/or change in skin potential response or respiratory activity rates). These arousals were shortlived, with the subjects returning to sleep even with continuing or increased stimulus intensity. Neither the incidence of partial arousals nor the associated threshold intensities differentiated subject groups. Although increased skin potential response activity and decreased respiratory rates were observed during sleep relative to wakefulness, and a predominance of skin potential response activity was noted in stage 4 sleep, no significant differences in frequency (rate/min) of autonomic response measures were obtained when rates before and during auditory stimulation were compared.