Fetal responses to vibrotactile stimulation, a possible predictor of fetal and neonatal outcome

Third Trimester Fetuses Demonstrate Priming, a Form of Implicit Memory, In Utero

Research examinations of changes in fetal heart rate (HR) to operationalize fetal memory suggests that human memory capacities emerge in utero. However, there is little evidence for a form of implicit memory or priming. The present aim was to determine if priming is evident in utero. Fetal HR, maternal HR and maternal respiratory rate (RR) were examined in 105 women during the third trimester of pregnancy. Women experienced two counterbalanced laboratory tasks, the Stroop task and the paced breathing task, and their cardiorespiratory activity functioned as a stimulus for fetuses. Repeated measures ANOVAs revealed maternal HR increased during the Stroop task but only when the Stroop task was presented first (89.64 bpm to 92.39 bpm) (p = 0.04). Maternal RR increased during the Stroop task, regardless of task order (17.72 bpm to 21.11 bpm; 18.50 bpm to 22.60 bpm) (p < 0.01). Fetal HR increased during the paced breathing task, but only when it followed maternal exposure to the Stroop task (141.13 bpm to 143.97 bpm) (p < 0.01). Fetuses registered maternal HR and RR reactivity to the Stroop task, which influenced their response during maternal engagement with a related task, suggesting priming. Further study of fetal memory may suggest another pathway by which prenatal exposures impact future development.

Changes in event-related brain responses and habituation during child development - A systematic literature review

OBJECTIVE

This systematic review highlights the influence of developmental changes of the central nervous system on habituation assessment during child development. Therefore, studies on age dependant changes in event-related brain responses as well as studies on behavioural and neurophysiological habituation during child development are compiled and discussed.

METHODS

Two PubMed searches with terms "(development evoked brain response (fetus OR neonate OR children) (electroencephalography OR magnetoencephalography))" and with terms "(psychology habituation (fetal OR neonate OR children) (human brain))" were performed to identify studies on developmental changes in event-related brain responses as well as habituation studies during child development.

RESULTS

Both search results showed a wide diversity of subjects' ages, stimulation protocols and examined behaviour or components of event-related brain responses as well as a demand for more longitudinal study designs.

CONCLUSIONS

A conclusive statement about clear developmental trends in event-related brain responses or in neurophysiological habituation studies is difficult to draw. Future studies should implement longitudinal designs, combination of behavioural and neurophysiological habituation measurement and more complex habituation paradigms to assess several habituation criteria.

SIGNIFICANCE

This review emphasizes that event-related brain responses underlie certain changes during child development which should be more considered in the context of neurophysiological habituation studies.

Blocked, delayed, or obstructed: What causes poor white matter development in intrauterine growth restricted infants?

Poor white matter development in intrauterine growth restricted (IUGR) babies remains a major, untreated problem in neonatology. New therapies, guided by an understanding of the mechanisms that underlie normal and abnormal oligodendrocyte development and myelin formation, are required. Much of our knowledge of the mechanisms that underlie impaired myelination come from studies in adult demyelinating disease, preterm brain injury, or experimental models of hypoxia-ischemia. However, relatively less is known for IUGR which is surprising because IUGR is a leading cause of perinatal mortality and morbidity, second only to premature birth. IUGR is also a significant risk factor for the later development of cerebral palsy, and is a greater risk compared to some of the more traditionally researched antecedents - asphyxia and inflammation. Recent evidence suggests that the white matter injury and reduced myelination in the brains of some preterm babies is due to impaired maturation of oligodendrocytes thereby resulting in the reduced capacity to synthesize myelin. Therefore, it is not surprising that the hypomyelination observable in the central nervous system of IUGR infants has similarly lead to investigations identifying a delay or blockade in the progress of maturation of oligodendrocytes in these infants. This review will discuss current ideas thought to account for the poor myelination often present in the neonate's brain following IUGR, and discuss novel interventions that are promising as treatments that promote oligodendrocyte maturation, and thereby repair the myelination deficits that otherwise persist into infancy and childhood and lead to neurodevelopmental abnormalities.

Neuromagnetic signatures of syllable processing in fetuses and infants provide no evidence for habituation

BACKGROUND

Habituation, as a basic form of learning, is characterized by decreasing amplitudes of neuronal reaction following repeated stimuli. Recent studies indicate that habituation to pure tones of different frequencies occurs in fetuses and infants.

AIMS

Neural processing of different syllables in fetuses and infants was investigated.

STUDY DESIGN

An auditory habituation paradigm including two different sequences of syllables was presented to each subject. Each sequence consisted of eight syllables (sequence /ba/: 5× /ba/, 1× /bi/ (dishabituator), 2× /ba/; sequence /bi/: 5× /bi/, 1× /ba/ (dishabituator), 2× /bi/). Each subject was stimulated with 140 sequences. Neuromagnetic signatures of auditory-evoked responses (AER) were recorded by fetal magnetoencephalography (fMEG).

SUBJECTS

Magnetic brain signals of N=30 fetuses (age: 28-39weeks of gestation) and N=28 infants (age: 0-3months) were recorded. Forty-two of the 60 fetal recordings and 29 of the 58 infant recordings were included in the final analysis.

OUTCOME MEASURES

AERs were recorded and amplitudes were normalized to the amplitude of the first stimulus.

RESULTS

In both fetuses and infants, the amplitudes of AERs were found not to decrease with repeated stimulation. In infants, however, amplitude of syllable 6 (dishabituator) was significantly increased compared to syllable 5 (p=0.026).

CONCLUSIONS

Fetuses and infants showed AERs to syllables. Unlike fetuses, infants showed a discriminative neural response to syllables. Habituation was not observed in either fetuses or infants. These findings could be important for the investigation of early cognitive competencies and may help to gain a better understanding of language acquisition during child development.

STUDIES IN FETAL BEHAVIOR: REVISITED, RENEWED, AND REIMAGINED

Among the earliest volumes of this monograph series was a report by Lester Sontag and colleagues, of the esteemed Fels Institute, on the heart rate of the human fetus as an expression of the developing nervous system. Here, some 75 years later, we commemorate this work and provide historical and contemporary context on knowledge regarding fetal development, as well as results from our own research. These are based on synchronized monitoring of maternal and fetal parameters assessed between 24 and 36 weeks gestation on 740 maternal-fetal pairs compiled from eight separate longitudinal studies, which commenced in the early 1990s. Data include maternal heart rate, respiratory sinus arrhythmia, and electrodrmal activity and fetal heartrate, motor activity, and their integration. Hierarchical linear modeling of developmental trajectories reveals that the fetus develops in predictable ways consistent with advancing parasympathetic regulation. Findings also include:within-fetus stability (i.e., preservation of rank ordering over time) for heart rate, motor, and coupling measures; a transitional period of decelerating development near 30 weeks gestation; sex differences in fetal heart rate measures but not in most fetal motor activity measures; modest correspondence in fetal neurodevelopment among siblings as compared to unrelated fetuses; and deviations from normative fetal development in fetuses affected by intrauterine growth restriction and other conditions. Maternal parameters also change during this period of gestation and there is evidence that fetal sex and individual variation in fetal neurobehavior influence maternal physio-logical processes and the local intrauterine context. Results are discussed within the framework of neuromaturation, the emergence of individual differences, and the bidirectional nature of the maternal-fetal relationship.We pose a number of open questions for future research. Although the human fetus remains just out of reach, new technologies portend an era of accelerated discovery of the earliest period of development

Fetal vibroacoustic stimulation for facilitation of tests of fetal wellbeing

BACKGROUND

Acoustic stimulation of the fetus has been suggested to improve the efficiency of antepartum fetal heart rate testing.

OBJECTIVES

To assess the advantages and disadvantages of the use of fetal vibroacoustic stimulation in conjunction with tests of fetal wellbeing.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (30 September 2013).

SELECTION CRITERIA

All published and unpublished randomised controlled trials assessing the merits of the use of fetal vibroacoustic stimulation in conjunction with tests of fetal wellbeing.

DATA COLLECTION AND ANALYSIS

All review authors independently extracted data and assessed trial quality. Authors of published and unpublished trials were contacted for further information.

MAIN RESULTS

Altogether 12 trials with a total of 6822 participants were included. Fetal vibroacoustic stimulation reduced the incidence of non-reactive antenatal cardiotocography test (nine trials; average risk ratio (RR) 0.62, 95% confidence interval (CI) 0.48 to 0.81). Vibroacoustic stimulation compared with mock stimulation evoked significantly more fetal movements when used in conjunction with fetal heart rate testing (one trial, RR 0.23, 95% CI 0.18 to 0.29).

AUTHORS' CONCLUSIONS

Vibroacoustic stimulation offers benefits by decreasing the incidence of non-reactive cardiotocography and reducing the testing time. Further randomised trials should be encouraged to determine not only the optimum intensity, frequency, duration and position of the vibroacoustic stimulation, but also to evaluate the efficacy, predictive reliability, safety and perinatal outcome of these stimuli with cardiotocography and other tests of fetal wellbeing.

Auditory habituation in the fetus and neonate: an fMEG study

Habituation--the most basic form of learning--is used to evaluate central nervous system (CNS) maturation and to detect abnormalities in fetal brain development. In the current study, habituation, stimulus specificity and dishabituation of auditory evoked responses were measured in fetuses and newborns using fetal magnetoencephalography (fMEG). An auditory habituation paradigm consisting of 100 trains of five 500 Hz tones, one 750 Hz tone (dishabituator) and two more 500 Hz tones, respectively, were presented to 41 fetuses (gestational age 30-39 weeks) and 22 newborns or babies (age 6-89 days). A response decrement between the first and fifth tones (habituation), an increment between the fifth tone and the dishabituator (stimulus specificity) and an increment between the fifth (last tone before the dishabituator) and seventh tones (first tone after the dishabituator) (dishabituation) were expected. Fetuses showed weak responses to the first tone. However, a significant response decrement between the second and fifth tones (habituation) and a significant increment between the fifth tone and the dishabituator (stimulus specificity) were found. No significant difference was found for dishabituation nor was a developmental trend found at the group level. From the neonatal data, significant values for stimulus specificity were found. Sensory fatigue or adaptation was ruled out as a reason for the response decrement due to the strong reactions to the dishabituator. Taken together, the current study used fMEG to directly show fetal habituation and provides evidence of fetal learning in the last trimester of pregnancy.

Vibroacoustic stimulation for fetal assessment in labour in the presence of a nonreassuring fetal heart rate trace

BACKGROUND

Fetal vibroacoustic stimulation (VAS) is a simple, non-invasive technique where a device is placed on the maternal abdomen over the region of the fetal head and sound is emitted at a predetermined level for several seconds. It is hypothesised that the resultant startle reflex in the fetus and subsequent fetal heart rate (FHR) acceleration or transient tachycardia following VAS provide reassurance of fetal well-being. This technique has been proposed as a tool to assess fetal well-being in the presence of a nonreassuring cardiotocographic (CTG) trace during the first and second stages of labour.

OBJECTIVES

To evaluate the clinical effectiveness and safety of VAS in the assessment of fetal well-being during labour, compared with mock or no stimulation for women with a singleton pregnancy exhibiting a nonreassuring FHR pattern.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (6 September 2012) and reference lists of all retrieved articles. We sought unpublished trials and abstracts submitted to major international congresses and contacted expert informants.

SELECTION CRITERIA

All published and unpublished randomised trials that compared maternal and fetal/neonatal/infant outcomes when VAS was used to evaluate fetal status in the presence of a nonreassuring CTG trace during labour, compared with mock or no stimulation.

DATA COLLECTION AND ANALYSIS

Two review authors independently sought to assess for inclusion all the potential studies we identified as a result of the search strategy. We planned to resolve any disagreement through discussion or, if required, to consult a third person. Where there was uncertainty about a particular study, we attempted to contact study authors for additional information. However, these attempts were unsuccessful.

MAIN RESULTS

The search strategies yielded six studies for consideration of inclusion. However, none of these studies fulfilled the requirements for inclusion in this review.

AUTHORS' CONCLUSIONS

There are currently no randomised controlled trials that address the safety and efficacy of VAS used to assess fetal well-being in labour in the presence of a nonreassuring CTG trace. Although VAS has been proposed as a simple, non-invasive tool for assessment of fetal well-being, there is insufficient evidence from randomised trials on which to base recommendations for use of VAS in the evaluation of fetal well-being in labour in the presence of a nonreassuring CTG trace.

Fetal habituation in assisted conception

BACKGROUND

Neurodevelopment outcomes of children conceived by Assisted Reproductive Technology (ART)have been the subject of much recent attention. To date there are no reports of neurodevelopmental performance before birth in this group.

AIMS

To compare habituation (a measure of brain function) in fetuses conceived by assisted reproduction techniques (ART) with naturally conceived (NC) fetuses.

STUDY DESIGN

Case control study.

SUBJECTS

Women with singleton pregnancies matched for maternal age, parity and smoking were recruited in 2 groups: ART (n=20) and NC (n=20).

OUTCOME MEASURES

Sound stimuli (250 Hz, 110 dB) at 10 second intervals lasting 2 s were administered to the fetus. The end point was habituation (cessation of movement for five consecutive stimuli) or a maximum of 30 stimuli. Responses of the fetus were observed with ultrasound at 28, 32 and 36 weeks' gestation, video-recorded and anonymised for analysis.

RESULTS

At 28 weeks' gestation significantly more ART fetuses responded to sound of 250 Hz, 110 dB (p=0.02) but this difference did not persist at 32 and 36 weeks'. There was a significant increase in nonresponders as gestation advanced in the ART group. There was no difference in habituation or mean number of trials to habituate at all three gestations.

CONCLUSIONS

ART fetuses demonstrated no differences in habituation suggesting that there is no neurodevelopment delay. However, a decrease in response to sound as gestation advances might be a harbinger for poor perinatal outcomes and needs exploration.

Fetal vibroacoustic stimulation in computerized cardiotocographic analysis: the role of short-term variability and approximate entropy

The aim of this study was to evaluate the impact of vibroacoustic stimulation (VAS) on computerized cardiotocography short-term variability (STV) and approximate entropy (ApEn) in both low- and high-risk pregnancies. VAS was performed on 121 high- and 95 low-risk pregnancies after 10 minutes of continuous quiet, while their FHR parameters were monitored and recorded by cCTG analysis. Fetal heart rate was recorded using a computer-assisted equipment. Baseline FHR, accelerations, decelerations, STV, long-term irregularity (LTI), ApEn, and fetal movements (FMs) were calculated for defined observational periods before VAS and after 10 minutes. Data were also investigated in relationship with the perinatal outcome. In each group of patients, FHR after VAS remained almost unmodified. Fetal movements significantly increased after VAS in both groups. Results show that only in the high-risk pregnancies, the increase of STV and the decrease of ApEn after VAS were significantly associated with favorable perinatal outcomes.

[Fetal pain and intrauterine analgesia/anesthesia--long-term pathologic effects, causes and alleviation of intrauterine pain]

The human fetus can suffer several presumably painful interventions perinatally and even before, during its intrauterine life. In the past years, scientific dispute concerning the existence of fetal pain and the need for its relief has expanded, and a heated social, political, religious, moral and philosophical debate has arisen, focusing mainly on the suffering experienced by the fetus during artificial abortion. In our two connected papers, medical scientific knowledge regarding fetal pain in the literature is reviewed. In the first article published in Orvosi Hetilap volume 150, issue 11, we defined pain and the neuroanatomical structures participating in subjective pain perception, as well as the development of these structures. Then, the objective indicators of intrauterine stress response (such as fetal neuroendocrine, cardiovascular, reflex and behavioral reactions) evoked by noxious stimuli were discussed. The present second article gathers the evidence of long-term pathologic effects caused by early-experienced pain and stress in animal models and humans. Finally, the potentially pain-evoking pre- and perinatal interventions are evaluated, as well as the analgetic/anesthetic methods that can be applied to intrauterine fetuses in everyday obstetrical practice.

Fetal Habituation

One aim of obstetric practice is to ensure the wellbeing of the fetus. This is by no means an easy task and recent years have seen the development of a variety of tests, with varying degrees of success, to evaluate fetal health.

Fetal wellbeing may be assessed at a variety of levels: genetic/cellular, physical/structural or functional. Ideally the evaluation of fetal health should provide information about the functional outcome of any particular condition, especially the performance of the central nervous system. Current tests may not do this. Thus, whilst tests of the fetal chromosomal or genetic constitution may determine the presence of particular genetic/chromosomal conditions, they may not predict functional outcome especially the functioning of the cerebral cortices, the ultimate arbiter of excellence in man. For example, Down's syndrome may be accurately diagnosed by analysis of fetal cells to detect the presence of Trisomy 21 but this in itself provides little information on the subsequent functional performance of the individual. The development of tests of fetal heart function such as antenatal cardiotocography have provided a means of assessing cardiac function and, to a certain extent, the functioning of parts of the autonomic nervous system. However such tests can only indirectly assess cortical function.

Fetal Magnetoencephalography - Achievements and Challenges in the Study of Prenatal and Early Postnatal Brain Responses: A Review

Fetal magnetoencephalography (fMEG) is the only non-invasive method for investigating evoked brain responses and spontaneous brain activity generated by the fetus in utero. Fetal auditory as well as visual evoked fields have been successfully recorded in basic stimulus-response studies. Moreover, paradigms investigating precursors for cognitive development, such as habituation and mismatch response have been applied successfully with fMEG. These and other studies have shown that the prenatal stage of life could be an important indicator for later cognitive development. This review addresses the achievements of fMEG and constructively discusses its challenges. It concludes with proposals for future studies as well as with designated new applications. Fetal MEG is a promising, and to date it is the only non-invasive approach for the prenatal assessment of precursors for cognitive development. Future fMEG studies might even enable the diagnosis of developmental delays. Furthermore, fMEG could be critical for the implementation and evaluation of fetal intervention programs in at-risk populations.

FETAL PAIN

The concept of fetal pain is becoming more and more relevant since the possibilities for invasive intrauterine treatment are increasing. However, there is much debate as to whether the fetus is mature enough to be able to perceive pain. But what is ‘pain’? One cannot determine whether a fetus feels pain unless one has a conception of what pain is. There is a difference in opinion about what pain really is and that is also the difficulty in studies on fetal pain: we cannot simply ask the fetus whether or not it feels pain. We can only give indirect evidence of possible harmful effects of stressful stimuli on the developing fetus. In this review we will first explore the meaning of ‘pain’. We will then discuss fetal anatomic, neurophysiologic and behavioural development and the responses which are thought to be required to experience pain. Finally, we discuss some ethical considerations and suggestions on fetal anaesthesia.

Neonatal and fetal response decrement of evoked responses: a MEG study

OBJECTIVE

To investigate the response decrements of visual evoked responses (VER) in newborns and assess the applicability of this paradigm to fetuses in magnetoencephalographic (MEG) recordings.

METHODS

Twelve newborns with no known risks or complications participated at chronological ages between 6 and 22days. They constituted the follow-up group to a prenatal study conducted on a sample of 25 fetuses whose gestational age (GA) varied between 29 and 37weeks at the time of recording. Trains of four light flashes with an interstimulus interval of 2s followed by 10s without stimulation were delivered to record VER.

RESULTS

Nine of the 12 newborns responded to the stimulation and showed response decrements in amplitude from the first to the last light flash. Furthermore, the response latency increased significantly from the first to the last stimulus. The remaining three recordings were discontinued early. Even though the prenatal visual evoked response rate was only 29%, the fetuses exhibited a response decrement after the first stimulus.

CONCLUSIONS

The amplitude of VERs can be used to elicit a response decrement in newborns and, with limitations, even in fetuses. This paradigm might be a useful tool for a direct non-invasive assessment of neonatal and prenatal brain development and CNS functioning.

SIGNIFICANCE

The proposed method might be a first step towards an early detection of developmental deficits in newborns and fetuses.

Neurodevelopmental changes of fetal pain

Pain in the developing fetus is controversial because of the difficulty in measuring and interpreting pain during gestation. It has received increased attention lately because of recently introduced legislation that would require consideration of fetal pain during intentional termination of pregnancy. During development, sensory fibers are abundant by 20 weeks; a functional spinal reflex is present by 19 weeks; connections to the thalamus are present by 20 weeks; and connections to subplate neurons are present by 17 weeks with intensive differentiation by 25 weeks. These cells are important developmentally, but decline as a result of natural apoptosis. Mature thalamocortical projections are not present until 29 to 30 weeks, which has led many to believe the fetus does not experience emotional "pain" until then. Pain requires both nociception and emotional reaction or interpretation. Nociception causes physiologic stress, which in turn causes increases in catecholamines, cortisol, and other stress hormones. Physiological stress is different from the emotional pain felt by the more mature fetus or infant, and this stress is mitigated by pain medication such as opiates. The plasticity of the developing brain makes it vulnerable to the stressors that cause long-term developmental changes, ultimately leading to adverse neurological outcomes. Whereas evidence for conscious pain perception is indirect, evidence for the subconscious incorporation of pain into neurological development and plasticity is incontrovertible. Scientific data, not religious or political conviction, should guide the desperately needed research in this field. In the meantime, it seems prudent to avoid pain during gestation.

Prenatal stress, the hypothalamic-pituitary-adrenal axis, and fetal and infant neurobehaviour

BACKGROUND

Although it has long been acknowledged that chronic HPA axis dysregulation impacts on adult neural function, little attention has been paid to the impact that disturbances of the maternal HPA axis may have on the developing fetal brain.

AIM

This editorial examines the associations between prenatal stress, neuroendocrine functioning, and behavioural outcome in both animal and human offspring, with a particular focus on the relationship between prenatal stress and human fetal and infant neurobehaviour.

STUDY DESIGN

Using electronic databases, a computerized search of published and unpublished data was undertaken.

RESULTS

There is growing evidence that prenatal stress impacts on offspring neural function and behaviour in animal populations. That these findings may be applicable to human fetal neurobehaviour and infant development and outcome is gaining research attention, and the potential importance of the timing of pregnancy stress is being increasingly highlighted.

CONCLUSIONS

There is a pressing need for more research into the role of maternal stress and anxiety during pregnancy on human fetal and infant outcomes. Future studies should prospectively pair physiological and psychological measures both pre- and postnatally if the HPA axis function of the mother and her infant is to be more fully understood.

Vibroacoustic stimulation for fetal assessment in labour in the presence of a nonreassuring fetal heart rate trace

BACKGROUND

Fetal vibroacoustic stimulation is a simple, non-invasive technique where a device is placed on the maternal abdomen over the region of the fetal head and sound is emitted at a predetermined level for several seconds. It is hypothesized that the resultant startle reflex in the fetus and subsequent fetal heart rate acceleration or transient tachycardia following vibroacoustic stimulation provide reassurance of fetal well-being. This technique has been proposed as a tool to assess fetal well-being in the presence of a non-reassuring cardiotocographic trace during the first and second stages of labour.

OBJECTIVES

To evaluate the clinical effectiveness and safety of vibroacoustic stimulation in the assessment of fetal well-being during labour, compared with mock or no stimulation for women with a singleton pregnancy exhibiting a non-reassuring fetal heart rate pattern.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group Trials Register (30 September 2004), the Cochrane Central Register of Controlled Trials (The Cochrane Library, Issue 1, 2004), MEDLINE (January 1966 to January 2005), EMBASE (January 1966 to January 2005) and reference lists of all retrieved articles. We sought unpublished trials and abstracts submitted to major international congresses and contacted expert informants.

SELECTION CRITERIA

All published and unpublished randomised trials that compared maternal and fetal/neonatal/infant outcomes when vibroacoustic stimulation was used to evaluate fetal status in the presence of a non-reassuring cardiotocographic trace during labour, compared with mock or no stimulation.

DATA COLLECTION AND ANALYSIS

Two independent review authors identified potential studies from the literature search and assessed them for methodological quality and appropriateness of inclusion, using a data extraction form. Attempts to contact study authors for additional information were unsuccessful.

MAIN RESULTS

The search strategies yielded six studies for consideration of inclusion. However, none of these studies fulfilled the requirements for inclusion in this review.

AUTHORS' CONCLUSIONS

There are currently no randomised controlled trials that address the safety and efficacy of vibroacoustic stimulation used to assess fetal well-being in labour in the presence of a non-reassuring cardiotocographic trace. Although vibroacoustic stimulation has been proposed as a simple, non-invasive tool for assessment of fetal well-being, there is insufficient evidence from randomised trials on which to base recommendations for use of vibroacoustic stimulation in the evaluation of fetal well-being in labour in the presence of a non-reassuring cardiotocographic trace.

Fetal rate of behavioral inhibition and preference for novelty during infancy

BACKGROUND

Correlations between infant measures of information processing and later IQ have been established, and a few studies have extended this continuum by examining links between various fetal measures and cognitive measures during infancy.

AIMS

This study compared fetal rate of behavioral habituation among infants identified as at high or low cognitive risk.

STUDY DESIGN

This study was a retrospective examination of differences in fetal rate of behavioral habituation as a function of cognitive risk status at 6.5 and 9 months postpartum, using an independent two-group design.

SUBJECTS

Participants were 32 infants who were born between 36 and 42 weeks gestational age at normal birth weight and had normal APGAR scores.

OUTCOME MEASURES

The Fagan Test of Infant Intelligence (FTII) was used to obtain a measure of preference for novelty, which served as the basis for identification of infants at high or low risk for cognitive difficulty. These infants had undergone up to three habituation trials using a vibroacoustic stimulus during fetal development.

RESULTS

Infants who were classified as being at high cognitive risk at 6 months had required more trials to habituation as fetuses.

CONCLUSIONS

Fetal rate of behavioral habituation is associated with information processing during the first 6 months of infancy. We suggest that fetal habituation may be influenced by early cognitive mechanisms and therefore represents an immature but real form of information processing.

Neurobehavioral assessment before birth

The complexities of neurobehavioral assessment of the fetus, which can be neither directly viewed nor manipulated, cannot be understated. Impetus to develop methods for measuring fetal neurobehavioral development has been provided by the recognition that individual differences in neurobehavioral functioning do not originate with birth and acceptance of the key contribution of the antenatal period to postnatal life. Research has centered around four aspects of fetal functioning: heart rate, motor activity, behavioral state, and responsivity to stimulation. Longitudinal studies have revealed that the developmental trajectories of these characteristics parallel the developing nervous system, detected a transitional period between 28 and 32 weeks gestation, and established within-fetal stability during the second half of gestation. Despite the promise of fetal stimulation and habituation paradigms as measures of neural functioning, significant safety and ethical concerns exist. Construction of a unified fetal neurobehavioral scale is premature until a sufficient degree of normative data is available and the predictive validity of specific aspects of fetal neurobehavior to child developmental outcomes is better established.

Maternal alcohol consumption during pregnancy and fetal startle behaviour

The startle behaviour of the fetus (both spontaneous and elicited) was examined in fetuses of mothers who drank alcohol and mothers who did not. Fetuses exposed to alcohol showed a higher frequency of spontaneous startles and were less likely to exhibit a normal startle in response to a vibroacoustic stimulus. These differences illustrate a teratogenic effect of alcohol on CNS functioning in utero, possibly associated with brainstem damage.

Fetal vibroacoustic stimulation for facilitation of tests of fetal wellbeing

BACKGROUND

Acoustic stimulation of the fetus has been suggested to improve the efficiency of antepartum fetal heart rate testing.

OBJECTIVES

The objective of this review was to assess the merits or adverse effects of the use of fetal vibroacoustic stimulation in conjunction with tests of fetal wellbeing.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group trials register. Date of last search: October 2000.

SELECTION CRITERIA

All published and unpublished randomized controlled trials assessing the merits of the use of fetal vibroacoustic stimulation in conjunction with tests of fetal wellbeing.

DATA COLLECTION AND ANALYSIS

Both reviewers independently extracted data and assessed trial quality. Authors of published and unpublished trials were contacted for further information.

MAIN RESULTS

A total of seven trials with a total of 4325 participants were included. Fetal vibroacoustic stimulation reduced the incidence of non-reactive antenatal cardiotocography test (odds ratio (OR) 0.61, 95% confidence interval (CI) 0.49-0.75) and reduced the overall mean cardiotocography testing time (weighted mean difference (WMD) -4.55 minutes, 95% CI -5.96 minutes to -3.14 minutes). Vibroacoustic stimulation evoked more than mock stimulation when used in conjunction with fetal heart rate testing (OR 0.08, 95% CI 0.06-0.12).

REVIEWER'S CONCLUSIONS

Vibroacoustic stimulation offers benefits by decreasing the incidence of non-reactive cardiotocography and reducing the testing time. Further randomized trials should be encouraged to determine not only the optimum intensity, frequency, duration and position of the vibroacoustic stimulation, but also to evaluate the efficacy, predictive reliability, safety and perinatal outcome of these stimuli with cardiotocography and other tests of fetal wellbeing.

Habituation in fetuses of diabetic mothers

Fetuses of diabetic mothers exhibit maturational delays in their behaviour and disturbances in behavioural and intellectual functioning in childhood. This suggests an effect of maternal diabetes on the central nervous system of the fetus. The habituation technique enables the functioning of the higher central nervous system to be examined. A normal habituation pattern reflects an intact central nervous system. Previous studies have found abnormalities in the fetal central nervous system are reflected in habituation performance. This paper examined the habituation ability of fetuses of diabetic mothers and of non-diabetic mothers. The fetuses were tested at 28, 32 and 36 weeks of gestation. After 2 min of fetal inactivity a series of vibroacoustic stimuli were presented to the fetus. This continued until no response was observed on five consecutive stimulus presentations. The number of stimulus presentations to habituate at each gestational age was recorded. The results reveal that there was a highly significant main effect of group (F(1,47)=19.65, P<0.001). Fetuses of diabetic pregnancies took longer to habituate. There was a significant effect of gestational age (F(2,94)=44.67, P<0.0001). In both groups the number of trials to habituate decreased with advancing gestation. There was no relationship between random blood glucose levels and habituation performance. The results demonstrate that maternal diabetes affects higher aspects of central nervous system functioning in the fetus.

Fetal pain?

During the last few years a vivid debate, both scientifically and emotionally, has risen in the medical literature as to whether a fetus is able to feel pain during abortion or intrauterine surgery. This debate has mainly been inspired by the demonstration of various hormonal or motor reactions to noxious stimuli at very early stages of fetal development. The aims of this paper are to review the literature on development of the pain system in the fetus, and to speculate about the relationship between "sensing" as opposed to "feeling" pain and the number of reactions associated with painful stimuli. While a cortical processing of pain theoretically becomes possible after development of the thalamo-cortical connections in the 26th week of gestation, noxious stimuli may trigger complex reflex reactions much earlier. However, more important than possible painfulness is the fact that the noxious stimuli, by triggering stress responses, most likely affect the development of an individual at very early stages. Hence, it is not reasonable to speculate on the possible emotional experiences of pain in fetuses or premature babies. A clinically relevant aim is rather to avoid and/or treat any possibly noxious stimuli, and thereby prevent their potential adverse effects on the subsequent development.

Fetal sensory competencies

A growing body of evidence is available about the functioning of fetal sensory systems during gestation. This article aims at reviewing data concerning (i) the presence of potential sensory stimulation in the fetal milieu, (ii) the sequential functional development of the sensory systems and (iii) physiological and behavioral responses of fetuses to various types of stimulation. Human data are compared with data collected in other mammalian species. Most studies have investigated auditory and chemosensory (olfactory and gustatory) responsiveness of the fetus in the second half of gestation. They demonstrate that (i) motor and heart rate responsiveness depends on gestational age and characteristics of stimulation; (ii) fetal sensory experience has short- and long-term effects at morphological, functional and behavioral levels (for example transnatal learning). The clinical consequences of the fetal sensory functioning are developed.

Motor responsivity during habituation testing of normal human fetuses

Features of fetal motor responsivity include both the magnitude of the startle response elicited by a single stimulus (i.e., basal reactivity) and the ease by which responding to successive stimuli is inhibited (i.e., habituation). We examined basal motor reactivity and habituation of the motor response in 56 normal human fetuses between 34 and 40 weeks of gestation. Testing consisted of 8 trials of a 1-sec vibroacoustic stimulus (VAS) with a 10-sec interstimulus interval. A score of 0-10 was assigned for each trial based on subjective assessment of intensity and duration of the fetal motor response. Measures of habituation included the ratio of responding after a fixed number of trials divided by the initial response, and the rate of change in the behavioral response over trials. No relationship was found between the rate of motor habituation and either basal reactivity, gestational age, or prestimulus fetal heart rate (FHR) variability. In contrast, more mature fetuses responded less intensely to the first stimulus than did their younger counterparts (r = -0.329, p = 0.005), and fetuses who were initially in a quiet state exhibited a more vigorous startle response as compared to fetuses who were initially in a more active state (r = -0.372, p = 0.001). The relationship between basal reactivity and prestimulus FHR variability was statistically significant even after controlling for gestational age (r = 0.295, p = 0.01). These findings may have important clinical implications regarding the appearance in early life of certain behavioral tendencies such as temperament.

Frequency discrimination by the fetus

The ability to discriminate between acoustic signals of different frequencies is fundamental to the interpretation of auditory information and the development of language perception and production. The fact that the human fetus responds to sounds of different frequencies raises the question of whether the fetus is able to discriminate between them? To investigate whether the fetus has the ability to discriminate between different pure tone acoustic stimuli and different speech sounds the following study used an habituation paradigm and examined whether the fetus could discriminate between two pure tone acoustic stimuli, 250 Hz and 500 Hz, or two speech sounds, [ba] and [bi], at 27 and 35 weeks of gestational age. The results indicated that the fetus is capable of discriminating between the different sounds, i.e. 250 Hz and 500 Hz and [ba] and [bi] at 35 weeks of gestational age but less able at 27 weeks of gestational age. The implications of this for the development of the auditory system are discussed.

The effect of ethanol on habituation and the cardiovascular response to stimulation in fetal sheep

Fetal cardiovascular (CVS) changes, forelimb movements (FM) and rates of habituation to repeated stimulation, with suffusions of cold saline over the skin, were measured in 12 chronically catheterized fetal sheep aged 130-145 days. Stimulation of the fetuses caused a significant rise in heart rate (HR) (p less than 0.01) and blood pressure (BP) (p less than 0.001) and FM (p less than 0.01). When the ewe was given an intravenous (i.v.) infusion of ethanol which produced fetal ethanol levels of 87 +/- 1.1 mg/100 ml, the number of spontaneous FM decreased (p less than 0.05). After i.v. ethanol, repeated stimulation of the fetuses still caused an increase in FM (p less than 0.01) and a rise in HR (p less than 0.05) and BP (p less than 0.02) but the fetuses habituated more rapidly (7.25 +/- 1.28 stimuli) compared to control experiments performed prior to (21.5 +/- 3.57 stimuli) or after the ethanol (17.75 +/- 5.83, p less than 0.01). Fetal exposure to low concentrations of ethanol does affect the patterns of response and habituation of the developing fetal central nervous system.

Foetal learning: implications for psychiatry?

While many of the ideas presented concerning foetal learning and their implications for psychiatry are at present speculative, I would remind people of the words of Carmichael (1954): "a study of adult behaviour without consideration of its origin before birth is as incomplete as . . . the study of adult anatomy without reference to the embryology of the structures considered." It is folly to overlook the foetal period!

The changes in fetal habituation patterns due to a decrease in inspired maternal oxygen

Habituation is widely regarded as a basic form of learning. A fully functioning central nervous system is probably required for a normal habituation pattern. Habituation of the behavioural response to vibroacoustic stimulation was studied in 23 normal human fetuses whose gestational age was 36 or more weeks. Eighteen were tested whilst their mothers breathed either air or a 12% oxygen in nitrogen mixture. The test was repeated the following day with the order of the gases reversed. In addition five fetuses were tested while their mothers breathed air on both occasions. Of the 18 fetuses 17 had a normal habituation pattern when tested in air but only two had a normal pattern when their mothers breathed 12% O2. Four of the five fetuses tested both days in air had normal patterns on the second day. Altering the amount of inspired maternal O2 alters the fetal habituation pattern.

Intrapartum vibratory acoustic stimulation of the human fetus during episodes of decreased heart rate variability

The effects of intrapartum vibratory acoustic stimulation during periods of decreased fetal heart rate variability were studied in 25 healthy term fetuses. Fetal monitoring and real-time ultrasound scanning were used simultaneously to detect fetal response. Vibratory acoustic stimulation was provided by an artificial larynx generating a signal at 85 dB and 85 Hz. This stimulus was applied for 5 seconds on the maternal abdomen over the fetal head after a 20-minute period of decreased fetal heart rate variability. All fetuses reacted with an immediate fetal heart rate acceleration of at least 10 bpm (range: 10 to 35 bpm, mean +/- SD = 18.4 +/- 7.0), and 19 fetuses also had sudden fetal body movement. A deceleration of the fetal heart rate after the initial acceleration was observed in nine fetuses (range: 15 to 70 bpm, mean +/- SD = 45.5 +/- 16.5). The implications of these findings are discussed in relation to the possible use of fetal vibratory acoustic stimulation for intrapartum surveillance.