Heartmusic:
Graphic & Audio Display of  Maternal & Fetal HRV

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Maternal–Fetal Bonding

The period before birth is among the last developmental frontiers.  Increasing evidence suggests that prenatal experience has persisting influences on health and development across the lifespan. 

The mother is central to the fetal environment. Her condition sets the framework for the state and development of the fetus.

Maternal feelings and mood states are linked to hormones and neurotransmitters that travel through the blood stream and across the placenta to the developing brain of the unborn. Prolonged exposure to stress hormones, including adrenaline and cortisol, prime the growing brain to react in fight and flight mode --even when inappropriate—throughout life. Maternal emphasis on joy and love, on the other hand, bathes the growing brain in "feel-good" endorphins and neurohormones such as oxytocin, promoting a lifelong sense of well-being.

Prenatal stress is believed to be a factor in causing preterm birth, as well as full-term birth with low birth weight. Low birth weight is a risk factor for cardiovascular disease and high body mass. Childhood experiences in emotionally cold families increase the likelihood of poor mental and physical health later in life, and abuse in childhood is a well-known risk factor for depression, posttraumatic stress disorder, idiopathic chronic pain disorders, substance abuse, antisocial behavior, as well as obesity, diabetes, and cardiovascular disease. Chaos in the home environment is a key determinant of poor self-regulatory behaviors, a sense of helplessness and psychological distress, as well as increased body mass and elevated blood pressure.

Strong maternal behavior produces offspring that are more exploratory of novel environments and less emotionally reactive and produces a lower and more contained glucocorticoid stress response in novel situations; poor maternal care leads to offspring with increased emotional and HPA reactivity and less exploration of a novel situation. Effects of pre- and perinatal maternal care are transmitted across generations by the subsequent behavior of the female offspring as they become mothers, and methylation of DNA on key genes appears to play a role in this epigenetic transmission.

However, far from being an inert passenger in a pregnant mother, the foetus is very much in command of the pregnancy. It is the foetus who guarantees the endocrine success of pregnancy and induces all manner of changes in maternal physiology to make her a suitable host. It is the foetus who, single-handed, solves the homograft problem - no mean feat when we reflect that, biologically, it is quite possible for a woman to bear more than her own body weight of babies, all immunological foreigners, during her reproductive career. It is the foetus who determines the duration of pregnancy. It is the foetus who decides which way he will lie in pregnancy and which way he will present in labour. Even in labour the foetus is not entirely passive - neither the toothpaste in the tube nor the cork in the champagne bottle, as required by the old hydraulic theories of the mechanics of labour. Much of the behaviour of the neonate and infant can now be observed in utero and, by corollary, a better understanding of the foetus and his environment puts the behaviour and problems of the neonate in better perspective. (A.W. Liley, "The Foetus as a Personality," Australian and New Zealand Journal of Psychiatry (1972) Vol 6: 99)

There is a dynamic, bidirectional relationship between developing individuals and the environments in which they grow. Indeed, psychosocial functioning is the product of an individual’s actions on his or her environment and the actions of the environment on an individual.

Research has indicated that both physiology and parenting are thought to influence both adaptive and maladaptive development. This interaction can often be documented in the fetal heart rate, which remains one of the primary descriptors of fetal physiological activity accessible to systematic study.

It has long been theorized, but not empirically tested, that biological rhythms provide the foundation for social rhythms.

Both cardiac vagal tone and child-rearing practices are associated with young children’s abilities to regulate the experience of emotion.  Cardiac vagal tone is thought to be moderately stable, with individual differences remaining relatively similar from infancy to early childhood.  It also is the case that parenting styles are moderately stable in infancy and early childhood. However, little is known about factors that influence change and stability in parenting. Furthermore, factors associated with individual changes in cardiac vagal tone also have not been examined.

Physiologically, prenatal interaction between mother and fetus has been postulated and various studies confirm a relationship between maternal and fetal conditions on the basis of fetal heart rate. These studies show changes in fetal heart rate and heart rate variability (HRV) associated with altered maternal arterial oxygen content, maternal hypothermia and maternal exercise. Furthermore, links between maternal and fetal heart rate have been examined. A positive correlation between these rates has been found over periods of 1 and 24 h and the entrainment of the fetal heart rate rhythm to the maternal diurnal rhythm has been observed. However, short-term interaction between fetal and maternal heart rate is elusive.

A recently published article by Van Leeuwen et al. (Van Leeuwen P, et al. (2009) Influence of paced maternal breathing on fetal–maternal heart rate coordination. Proc Natl Acad Sci USA 106:13661–13666: http://www.pnas.org/content/early/2009/07/10/0901049106.full.pdf+html.) suggests that the fetal cardiac system possess the capability to adjust its rate of activation in response to external—i.e., maternal—stimulation. Hence, the pregnant mothers’ special awareness to the unborn child may also be reflected by fetal–maternal interaction of cardiac activity.

Using multichannel magnetocardiography to simultaneously record the magnetic fields generated during each maternal and fetal heartbeat at resting supine condition, Van Leeuwen et al. derive time series of consecutive heartbeat intervals, and they discover epochs of synchronization where fetal heartbeats occur at the same instantaneous phases within each consecutive maternal heartbeat cycle—the first evidence of direct coupling mediated by the maternal cardiac activity.

Heart Rate Variability

According to classical concepts of physiologic control, healthy systems are self-regulated to reduce variability and maintain physiologic constancy. In general, homeostatic processes are regulated by the parasympathetic nervous system via the vagus nerve. Contrary to the predictions of homeostasis, however, the output of a wide variety of systems, such as the normal human heartbeat, fluctuates in a complex manner, even under resting conditions.

While the rhythmic beating of the heart at rest was once believed to be monotonously regular, we now know that the rhythm of a healthy heart under resting conditions is actually surprisingly irregular. Heart rate variability (HRV), derived from the electrocardiogram (ECG), is a measurement of these naturally occurring, beat-to-beat changes in heart rate.

The changes in fetal heart rate (FHR) and fetal heart rate variability (FHRV) are not well understood, particularly since the fetal central nervous system may not be fully formed at birth. Nevertheless, interpretation of Fetal Heart Rate Monitoring has become an important assessment of fetal well being.
 
It is generally assumed that fetal heart rate variability increases with gestation, reflecting prenatal development of the autonomic nervous system. However, fetal heart rate complexity does not simply increase during pregnancy but short-term epochs with a high degree of regularity also become more frequent.

It is also known that the number of heart rate accelerations and decelerations per hour that a fetus experiences, may also be related to its health and is also a function of gestational age.

The increasing complexity in fetal HRV time-series in different gestational ages.

R. Sameni, _Extraction of Fetal Cardiac Signals from an Array of Maternal Abdominal Recordings, Ph.D. dissertation, Sharif University of Technology, Institut National Polytechnique de Grenoble, July 2008. [Online]. Available: http://www.sameni.info/Publications/Thesis/PhDThesis.pdf

Sonification

A hallmark of physiologic systems is their extraordinary complexity. The non-stationary and non-linear aspects of signals generated by living organisms defy traditional mechanistic approaches based on homeostasis and conventional bio-statistical methodologies. Recognition that physiologic time series contain ‘‘hidden information’’ has fueled growing interest in applying new concepts and techniques to a wide range of biomedical problems from molecular to organic-system levels. One such approach to examine the interaction between partly independent but partly closely linked physiological systems is sonification.

Sonification is defined as the use of nonspeech audio to convey information. More specifically, sonification is the transformation of data relations into perceived relations in an acoustic signal for the purposes of facilitating communication or interpretation. By its very nature, sonification is interdisciplinary, integrating concepts from human perception, acoustics, design, the arts, and engineering. Thus, development of effective auditory representations of data require interdisciplinary collaborations using the combined knowledge and efforts of psychologists, computer scientists, engineers, physicists, composers, and musicians, along with the expertise of specialists in the application areas being addressed.

Auditory perception can be effective for representing data in a variety of settings and is particularly sensitive to temporal characteristics or changes in sounds over time. Human hearing is well designed to discriminate between periodic and aperiodic events and can detect small changes in the frequency of continuous signals. This points to a distinct advantage of auditory over visual displays. Fast-changing or transient data that might be blurred or completely missed by visual displays may be easily detectable in even a primitive, but well designed auditory display.

Thus, sonification is useful for comprehending or monitoring complex temporal data, multiple auditory data sets and data that is embedded in other, more static, signals.

In the examples of heart rate sonification on this site, the instantaneous heart rate has been calculated at every new heart beat and given a musical note value, according to whether the rate is rising or falling. Accordingly, higher heart rates will produce higher notes; lower rates will produce lower notes. These notes are also instantaneously triggered by each new heart beat, thus preserving the temporal aspects of heart rate variability.  Longer or shorter inter-beat intervals will produce longer or shorter notes respectively. Also, the pitch will only change when the heart rate changes, so that a heart rate that remains constant over two or more beats will produce a note that will be held so long until the heart rate changes.

Through the importation of virtual sound or instrument libraries, the note values can be assigned to individual instrument recordings that are then modulated according to pitch and duration.

From fetal & maternal heart rate variability :

In the beginning of 2008  the fetal and maternal heart rates were  recorded simultaneously in realtime but the data was first converted into music at a later date. This was because the previously developed technology did not allow a realtime conversion into music. Due to this, some of the temporal relationships of maternal and fetal heart beats were lost.

In the example below, the maternal heart rate, about 70 bpm, is sonified as a cello and then, additionally, as a piano. The fetal heart rate, about 140 bpm, is sonified as a flute. For effect and clarity, the instruments are introduced offset.