Fetal cardiac autonomic control during breathing and non-breathing epochs: the effect of maternal exercise

Maternal physical activity in healthy pregnancy: Effect on fetal oxygen supply

AIM

We review evidence for effects of physical activity before and during gestation on the course of pregnancy and ask if there are circumstances where physical activity can stress the fetus due to competition for oxygen and energy substrates.

RESULTS

We first summarize physiological responses to exercise in nonpregnant people and known physiological adaptations to pregnancy. Comparing the two, we conclude that physical activity prior to and continuing during gestation is beneficial to pregnancy outcome. The effect of starting an exercise regimen during pregnancy is less easy to assess as few studies have been undertaken. Results from animal models suggest that the effects of maternal exercise on the fetus are transient; the fetus can readily compensate for a short-term reduction in oxygen supply.

CONCLUSION

In general, we conclude that physical activity before and during pregnancy is beneficial, and exercise started during pregnancy is unlikely to affect fetal development. We caution, however, that there are circumstances where this may not apply. They include the intensive exercise regimens of elite athletes and pregnancies at high altitudes where hypoxia occurs even in the resting state.

Correlation of fetal heart rate dynamics to inflammatory markers and brain-derived neurotrophic factor during pregnancy

OBJECTIVES

This study aims to show the relation between biomarkers in maternal and cord-blood samples and fetal heart rate variability (fHRV) metrics through a non-invasive fetal magnetocardiography (fMCG) technique.

METHODS

Twenty-three women were enrolled for collection of maternal serum and fMCG tracings immediately prior to their scheduled cesarean delivery. The umbilical cord blood was collected for measurement of biomarker levels. The fMCG metrics were then correlated to the biomarker levels from the maternal serum and cord blood.

RESULTS

Brain-derived neurotrophic factor (BDNF) had a moderate correlation with fetal parasympathetic activity (0.416) and fetal sympathovagal ratios (-0.309; -0.356). Interleukin (IL)-6 also had moderate-sized correlations but with an inverse relationship as compared to BDNF. These correlations were primarily in cord-blood samples and not in the maternal blood.

CONCLUSIONS

In this small sample-sized exploratory study, we observed a moderate correlation between fHRV and cord-blood BDNF and IL-6 immediately preceding scheduled cesarean delivery at term. These findings need to be validated in a larger population.

Exploring the Influence of Fetal Sex on Heart Rate Dynamics Using Fetal Magnetocardiographic Recordings

Fetal sex has been associated with different development trajectories that cause structural and functional differences between the sexes throughout gestation. Fetal magnetocardiography (fMCG) recordings from 123 participants (64 females and 59 males; one recording/participant) from a database consisting of low-risk pregnant women were analyzed to explore and compare fetal development trajectories of both sexes. The gestational age of the recordings ranged from 28 to 38 weeks. Linear metrics in both the time and frequency domains were applied to study fetal heart rate variability (fHRV) measures that reveal the dynamics of short- and long-term variability. Rates of linear change with GA in these metrics were analyzed using general linear model regressions with assessments for significantly different variances and GA regression slopes between the sexes. The fetal sexes were well balanced for GA and sleep state. None of the fHRV measures analyzed exhibited significant variance heterogeneity between the sexes, and none of them exhibited a significant sex-by-GA interaction. The absence of a statistically significant sex-by-GA interaction on all parameters resulted in none of the regression slope estimates being significantly different between the sexes. With high-precision fMCG recordings, we were able to explore the variation in fHRV parameters as it relates to fetal sex. The fMCG-based fHRV parameters did not show any significant difference in rates of change with gestational age between sexes. This study provides a framework for understanding normal development of the fetal autonomic nervous system, especially in the context of fetal sex.

The effect of maternal pregestational diabetes on fetal autonomic nervous system

Heart rate variability assessment of neonates of pregestational diabetic mothers have shown alterations in the autonomic nervous system (ANS). The objective was to study the effect of maternal pregestational diabetes on ANS at the fetal stage by combining cardiac and movement parameters using a non-invasive fetal magnetocardiography (fMCG) technique. This is an observational study with 40 participants where fetuses from a group of 9 Type 1, 19 Type 2 diabetic, and 12 non-diabetic pregnant women were included. Time and frequency domain fetal heart rate variability (fHRV) and coupling of movement and heart rate acceleration parameters related to fetal ANS were analyzed. Group differences were investigated using analysis of covariance to adjust for gestational age (GA). When compared to non-diabetics, the Type 1 diabetics had a 65% increase in average ratio of very low-frequency (VLF) to low-frequency (LF) bands and 63% average decrease in coupling index after adjusting for GA. Comparing Type 2 diabetics to non-diabetics, there was an average decrease in the VLF (50%) and LF bands (63%). Diabetics with poor glycemic control had a higher average VLF/LF (49%) than diabetics with good glycemic control. No significant changes at p < 0.05 were observed in high-frequency (HF) frequency domain parameters or their ratios, or in the time domain. Fetuses of pregestational diabetic mothers exhibited some differences in fHRV frequency domain and heart rate-movement coupling when compared to non-diabetics but the effect of fHRV related to fetal ANS and sympathovagal balance were not as conclusive as observed in the neonates of pregestational diabetic mothers.

Effects of Temporary Respiration Exercise with Individual Harmonic Frequency on Blood Pressure and Autonomic Balance

This study investigated the effects of modulated respiration on blood pressure and autonomic balance to develop a healthcare application system for stabilizing autonomic balance. Thirty-two participants were asked to perform self-regulated tasks with 18 different respiration sequences, and their electrocardiograms (ECG) and blood pressure were measured. Changes in cardiovascular system functions and blood pressure were compared between free-breathing and various respiration conditions. Systolic and diastolic blood pressures stabilized after individual harmonic breathing. Autonomic balance, characterized by heart rate variability, was also stabilized with brief respiration training according to harmonic frequency. Five machine-learning algorithms were used to classify the two opposing factors between the free and modulated breathing conditions. The random forest models outperformed the other classifiers in the training data of systolic blood pressure and heart rate variability. The mean areas under the curves (AUCs) were 0.82 for systolic blood pressure and 0.98 for heart rate variability. Our findings lend support that blood pressure and autonomic balance were improved by temporary harmonic frequency respiration. This study provides a self-regulated respiration system that can control and help stabilize blood pressure and autonomic balance, which would help reduce mental stress and enhance human task performance in various fields.

Towards better reliability in fetal heart rate variability using time domain and spectral domain analyses. A new method for assessing fetal neurological state?

OBJECTIVES

Fetal heart rate variability (FHRV) has shown potential in fetal surveillance. Therefore, we aimed to evaluate the reliability of time domain and spectral domain parameters based on non-invasive fetal electrocardiography (NI-FECG).

METHOD

NI-FECG, with a sampling frequency of 1 kHz, was obtained in 75 healthy, singleton pregnant women between gestational age (GA) 20+0 to 41+0. The recording was divided into a) heart rate pattern (HRP) and b) periods fulfilling certain criteria of stationarity of RR-intervals, termed stationary heart rate pattern (SHRP). Within each recording, the first and the last time series from each HRP with less than 5% artifact correction were analyzed and compared. Standard deviation of normal-to-normal RR-intervals (SDNN), root mean square of successive differences (RMSSD), high frequency power (HF-power), low frequency power (LF-power), and LF-power/HF-power were performed. A multivariate mixed model was used and acceptable reliability was defined as intraclass correlation coefficient (ICC) ≥ 0.80 and a coefficient of variation (CV) ≤ 15%. Based on these results, the CV and ICC were computed if the average of two to six time series was used.

RESULTS

For GA 28+0 to 34+6, SDNN and RMSSD exhibited acceptable reliability (CV < 15%; ICC > 90%), whereas GA 35+0 to 41+0and 20+0 to 27+6 showed higher CVs. Spectral domain parameters also showed high CVs However, by using the mean value of two to six time series, acceptable reliability in SDNN, RMSSD and HF-power from GA 28+0 was achieved. Stationarity of RR-intervals showed high influence on reliability and SHRP was superior to HRP, whereas the length of the time series showed minor influence.

CONCLUSION

Acceptable reliability seems achievable in SDNN, RMSSD and HF-power from gestational week 28. However, stationarity of RR-intervals should be considered when selecting time series for analyses.

Fetal Heart Rate Variability Is Affected by Fetal Movements: A Systematic Review

Introduction: Fetal heart rate variability (FHRV) evaluates the fetal neurological state, which is poorly assessed by conventional prenatal surveillance including cardiotocography (CTG). Accurate FHRV on a beat-to-beat basis, assessed by time domain and spectral domain analyses, has shown promising results in the scope of fetal surveillance. However, accepted standards for these techniques are lacking, and the influence of fetal breathing movements and gross movements may be especially challenging. Thus, current standards for equivalent assessments in adults prescribe rest and controlled respiration. The aim of this review is to clarify the importance of fetal movements on FHRV. Methods: A systematic review in accordance with the PRISMA guidelines based on publications in the EMBASE, the MEDLINE, and the Cochrane Library databases was performed. Studies describing the impact of fetal movements on time domain, spectral domain and entropy analyses in healthy human fetuses were reviewed. Only studies based on fetal electrocardiography or fetal magnetocardiography were included. PROSPERO registration number: CRD42018068806. Results: In total, 14 observational studies were included. Fetal movement detection, signal processing, length, and selection of appropriate time series varied across studies. Despite these divergences, all studies showed an increase in overall FHRV in the moving fetus compared to the resting fetus. Especially short-term, vagal mediated indexes showed an increase during fetal breathing movements including an increase in Root Mean Square of the Successive Differences (RMSSD) and High Frequency power (HF) and a decrease in Low Frequency power/High Frequency power (LF/HF). These findings were present even in analyses restricted to one specific fetal behavioral state defined by Nijhuis. On the other hand, fetal body movements seemed to increase parameters supposed to represent the sympathetic response [LF and Standard Deviation of RR-intervals from normal sinus beats (SDNN)] proportionally more than parameters representing the parasympathetic response (RMSSD, HF). Results regarding entropy analyses were inconclusive. Conclusion: Time domain analyses as well as spectral domain analyses are affected by fetal movements. Fetal movements and especially breathing movements should be considered in these analyses of FHRV.

Impact of maternal physical activity during an uncomplicated pregnancy on fetal and neonatal well-being parameters: a systematic review of the literature

We carried a thorough systematic review of the contemporary literature regarding the impact of maternal physical activity during pregnancy on the fetal and neonatal well-being parameters. We searched systematically publications indexed in PubMed and ScienceDirect, according to the PRISMA protocol. Studies examining following fetal and neonatal well-being parameters were included: fetal heart rate, active fetal movements, Doppler assessment of the placental and fetal circulations, amniotic fluid index, Apgar score, and umbilical cord blood acid-basis analysis at delivery. Altogether, 73 studies were identified (pooled sample size n = 7867). Out of these, 42 pertained to acute and 31 pertained to chronic exposure to maternal physical activity. The majority of the identified studies reported a positive or neutral effect of maternal physical activity on the fetal heart rate, Doppler-derived umbilical and cerebral blood flow parameters, and Apgar score. The literature regarding uterine arteries Doppler assessment, fetal active movements, amniotic fluid index, and umbilical cord blood acid-base analysis at delivery is sparse and does not allow us to generalize the inferences. Maternal physical activity during physiological pregnancy is safe for fetal and neonatal well-being when practiced according to recommendations. There is a need for better quality studies concerning the subject.

Heart rate variability for determining autonomic nervous system effects of lifestyle behaviors in early life: A systematic review

BACKGROUND

An unhealthy lifestyle negatively alters autonomic nervous system (ANS) activity as reflected by decreased heart rate variability (HRV), increasing cardiovascular disease (CVD) risk. Research investigating the effect of modifiable lifestyle factors on ANS activity in young children is limited. Early identification of these risk factors is vital to improving long-term individual and public health outcomes. A systematic review was conducted to assess the effect of maternal or child modifiable lifestyle factors on child ANS activity.

METHODS

Following the 2009 PRISMA guidelines, three electronic databases were searched from February 2018 - July 2019 for articles describing human trials between 1996 - 2019. Included studies examined ANS activity of children between 28 weeks gestational age - 6 years in relation to modifiable lifestyle CVD risk factors.

RESULTS

Twenty-six studies fulfilled inclusion criteria. Sixteen studies reported that modifiable lifestyle factors significantly influenced the HRV of children. Increased HRV was significantly associated with higher maternal zinc and omega-3 fatty acid intake, regular maternal aerobic exercise and a non-smoking environment. Child diet and body composition demonstrated some support for an association between these modifiable lifestyle factors and child HRV.

CONCLUSION

There is cross-sectional evidence supporting an association between maternal lifestyle factors and child HRV. Evidence is less supportive of a relationship between child modifiable lifestyle factors and child HRV. Monitoring the effects of lifestyle interventions on the ANS via HRV measurements of both mother and child may identify child CVD risk.

Spotlight on the fetus: how physical activity during pregnancy influences fetal health: a narrative review

Before and during pregnancy, women often aim to improve their lifestyle so as to provide a healthier environment for their developing child. It remains unresolved, however, as to whether physical activity (PA) during pregnancy poses a possible risk or whether it might even have beneficial effects on the developing child. There is increasing evidence that PA during pregnancy is indeed beneficial to maternal physiological and psychological health and that it is generally not detrimental to the fetal cardiovascular system and neuronal function in the developing child. This also led to international recommendations for PAs during pregnancy. In the current review, we aimed to comprehensively assess the evidence of beneficial and harmful effects of maternal PA, including high-performance sports, on fetal development. The different mental and body-based relaxation techniques presented here are frequently performed during pregnancy. We found a considerable number of studies addressing these issues. In general, neither low key, moderate maternal PA nor relaxation techniques were observed to have a harmful effect on the developing child. However, we identified some forms of PA which could have at least a transient unfavourable effect. Notably, the literature currently available does not provide enough evidence to enable us to make a general conclusive statement on this subject. This is due to the lack of longitudinal studies on the metabolic and cognitive effects of regular PA during pregnancy and the wide diversity of methods used. In particular, the kind of PA investigated in each study differed from study to study.

An Efficient Adaptive Filter for Fetal ECG Extraction Using Neural Network

Fetal electrocardiogram checking is a strategy for acquiring critical data about the state of the fetus during pregnancy and labor. This is done by measuring electrical signals created by the fetal heart as measured from multichannel potential recordings on the mother’s body surface. In any case, extraction of fetal signal is difficult because the signal is marred by the mother’s heartbeat signal. Subsequently, in this paper, a powerful versatile filtering strategy is utilized to eliminate the mother’s heartbeat signal with the specific end goal of extricating the fetal signal. The proposed procedure was executed in the working stage of MATLAB and the execution results were investigated.

Developmental milestones of the autonomic nervous system revealed via longitudinal monitoring of fetal heart rate variability

BACKGROUND

Fetal heart rate variability (fHRV) of normal-to-normal (NN) beat intervals provides high-temporal resolution access to assess the functioning of the autonomic nervous system (ANS).

AIM

To determine critical periods of fetal autonomic maturation. The developmental pace is hypothesized to change with gestational age (GA).

STUDY DESIGN

Prospective longitudinal observational study.

SUBJECTS

60 healthy singleton fetuses were followed up by fetal magnetocardiographic heart rate monitoring 4-11 times (median 6) during the second half of gestation.

OUTCOME MEASURE

FHRV parameters, accounting for differential aspects of the ANS, were studied applying linear mixed models over four predefined pregnancy segments of interest (SoI: <27; 27+0-31+0; 31+1-35+0; >35+1 weeks GA). Periods of fetal active sleep and quiescence were accounted for separately.

RESULTS

Skewness of the NN interval distribution VLF/LF band power ratio and complexity describe a saturation function throughout the period of interest. A decreasing LF/HF ratio and an increase in pNN5 indicate a concurrent shift in sympathovagal balance. Fluctuation amplitude and parameters of short-term variability (RMSSD, HF band) mark a second acceleration towards term. In contrast, fetal quiescence is characterized by sequential, but low-margin transformations; ascending overall variability followed by an increase of complexity and superseded by fluctuation amplitude.

CONCLUSIONS

An increase in sympathetic activation, connected with by a higher ability of parasympathetic modulation and baseline stabilization, is reached during the transition from the late 2nd into the early 3rd trimester. Pattern characteristics indicating fetal well-being saturate at 35 weeks GA. Pronounced fetal breathing efforts near-term mirror in fHRV as respiratory sinus arrhythmia.

Development and design of an intervention to improve physical activity in pregnant women using Text4baby

Text4baby is a free, mobile health information service for pregnant and post-partum women. This study aims to understand preferences of physical activity text messages (SMS), sequentially develop prototype SMS, and determine preferred dose of SMS to inform a future study utilizing Text4baby. This study had a user-centered design with three phases: (1) literature review and interviews with pregnant women for development of prototype SMS, (2) interviews with health care professionals and pregnant women for prototype SMS feedback, and (3) survey to determine preferred dose of SMS. Data from interviews identified knowledge and support as major themes. Prototypes were developed (N = 14) and informed 168 SMS. Pregnant women (N = 326) thought three SMS/week were about right (50.2 %) and preferred three SMS/week throughout pregnancy (71.9 %). There is a need for opportunities for behavioral scientists to incorporate evidence-based practices within scalable interventions. As such, this research will inform utilization of Text4baby to potentially improve physical activity participation.

Effect of maternal position on fetal behavioural state and heart rate variability in healthy late gestation pregnancy

KEY POINTS

Fetal behavioural state in healthy late gestation pregnancy is affected by maternal position. Fetal state 1F is more likely to occur in maternal supine or right lateral positions. Fetal state 4F is less likely to occur when the woman lies supine or semi-recumbent. Fetal state change is more likely when the woman is supine or semi-recumbent. Fetal heart rate variability is affected by maternal position with variability reduced in supine and semi-recumbent positions.

ABSTRACT

Fetal behavioural states (FBS) are measures of fetal wellbeing. In acute hypoxaemia, the human fetus adapts to a lower oxygen consuming state with changes in the cardiotocograph and reduced fetal activity. Recent studies of late gestation stillbirth described the importance of sleep position in the risk of intrauterine death. We designed this study to assess the effects of different maternal positions on FBS in healthy late gestation pregnancies under controlled conditions. Twenty-nine healthy women had continuous fetal ECG recordings under standardized conditions in four randomly allocated positions, left lateral, right lateral, supine and semi-recumbent. Two blinded observers, assigned fetal states in 5 min blocks. Measures of fetal heart rate variability were calculated from ECG beat to beat data. Compared to state 2F, state 4F was less likely to occur when women were semi-recumbent [odds ratio (OR) = 0.11, 95% confidence interval (95% CI) 0.02, 0.55], and supine (OR = 0.27, 95% CI 0.07, 1.10). State 1F was more likely on the right (OR = 2.36, 95% CI 1.11, 5.04) or supine (OR = 4.99, 95% CI 2.41, 10.43) compared to the left. State change was more likely when the mother was semi-recumbent (OR = 2.17, 95% CI 1.19, 3.95) or supine (OR = 2.67, 95% CI 1.46, 4.85). There was a significant association of maternal position to mean fetal heart rate. The measures of heart rate variability (SDNN and RMSSD) were reduced in both semi-recumbent and supine positions. In healthy late gestation pregnancy, maternal position affects FBS and heart rate variability. These effects are likely fetal adaptations to positions which may produce a mild hypoxic stress.

The influence of physical activity during pregnancy on maternal, fetal or infant heart rate variability: a systematic review

Background

Physical activity (PA) during pregnancy has been shown to be associated with several positive effects for mother, fetus, and offspring. Heart rate variability (HRV) is a noninvasive and surrogate marker to determine fetal overall health and the development of fetal autonomic nervous system. In addition, it has been shown to be significantly influenced by maternal behavior. However, the influence of maternal PA on HRV has not yet been systematically reviewed. Therefore, the aim of this systematic review was to assess the influence of regular maternal PA on maternal, fetal or infant HRV.

Methods

A systematic literature search following a priori formulated criteria of studies that examined the influence of regular maternal PA (assessed for a minimum period of 6 weeks) on maternal, fetal or infant HRV was performed in the databases Pubmed and SPORTDiscus. Quality of each study was assessed using the standardized Quality Assessment Tool for Quantitative Studies (QATQS).

Results

Nine articles were included into the present systematic review: two intervention studies, one prospective longitudinal study, and six post-hoc analysis of subsets of the longitudinal study. Of these articles four referred to maternal HRV, five to fetal HRV, and one to infant HRV. The overall global rating for the standardized quality assessment of the articles was moderate to weak. The articles regarding the influence of maternal PA on maternal HRV indicated contrary results. Five of five articles regarding the influence of maternal PA on fetal HRV showed increases of fetal HRV on most parameters depending on maternal PA. The article referring to infant HRV (measured one month postnatal) showed an increased HRV.

Conclusions

Based on the current evidence available, our overall conclusion is that the hypothesis that maternal PA influences maternal HRV cannot be supported, but there is a trend that maternal PA might increase fetal and infant HRV (clinical conclusion). Therefore, we recommend that further, high quality studies addressing the influence of maternal PA on HRV should be performed (methodological conclusion).

Differences in autonomic neural activity during exercise between the second and third trimesters of pregnancy

AIM

To test the hypothesis that autonomic neural activity in pregnant women during exercise varies according to gestational age.

METHODS

This cross-sectional study involved 20 healthy women in their second (n = 13) or third (n = 7) trimester of pregnancy. Incremental cardiopulmonary exercise testing was performed with an electromagnetic cycle ergometer. Heart rate variability was analyzed by frequency analysis software.

RESULTS

The low-frequency to high-frequency (LF/HF) ratio, an indicator of the sympathetic nervous system, was significantly higher in third trimester than in second trimester subjects (P < 0.05) at 1, 2, and 3 min of incremental exercise testing. In contrast, the HF/total power ratio, an indicator of rapidly acting parasympathetic activity, was significantly higher in second trimester than in third trimester subjects (P < 0.05) at 2 and 3 min. In addition, a negative correlation was found between gestational age and the 'accumulation half-time' of the LH/HF ratio, the time point at which the sum of the LF/HF ratio reached 50% of that accumulated in the total 6 min of exercise testing (r = -0.49, P = 0.028).

CONCLUSIONS

The autonomic response to exercise in pregnant women differs between the second and third trimesters. These differences should be considered when prescribing exercise to pregnant women.

Cardiac Physiology of Pregnancy

Although the physiology of the heart and vascular system has not changed, there are many things we have learned and are still learning today. Research related to heart adaptations during pregnancy has been performed since the 1930s. Since the mid-1950s, researchers began to look at changes in the maternal cardiovascular system during exercise while pregnant. Research related to exercise during pregnancy and offspring heart development began and has continued since the 1970s. We will review the normal female cardiovascular system adaptations to pregnancy in general. Additionally, topics related to maternal cardiac adaptations to pregnancy during acute exercise, as well as the chronic conditioning response from exercise training will be explored. Since physical activity during pregnancy influences fetal development, the fetal cardiac development will be discussed in regards to acute and chronic maternal exercise. Similarly, the influence of various types of maternal exercise on acute and chronic fetal heart responses will be described. Briefly, the topics related to how and if there is maternal-fetal synchrony will be explained. Lastly, the developmental changes of the fetal cardiovascular system that persist after birth will be explored. Overall, the article will discuss maternal cardiac physiology related to changes with normal pregnancy, and exercise during pregnancy, as well as fetal cardiac physiology related to changes with normal development, and exercise during pregnancy as well as developmental changes in offspring after birth.

Maternal Affective Illness in the Perinatal Period and Child Development: Findings on Developmental Timing, Mechanisms, and Intervention

Maternal mental illness is one of the most reliable risks for clinically significant child adjustment difficulties. The research literature in this area is very large and broad and dates back decades. In this review, we consider recent research findings on maternal mental illness and child development by focusing particularly on affective illness the perinatal period. We do this because maternal affective illness in the perinatal period is common; recent evidence suggests that pre- and postpartum maternal depression may have lasting effects on child behavioral and somatic health; research in the perinatal period raises acute and compelling questions about mechanisms of transmission and effect; and perinatal-focused interventions may offer distinct advantages for benefitting mother and child and gaining insights into developmental mechanisms. Throughout the review, we attend to the increasing integration of psychological and biological models and the trans-disciplinary approach now required for clinical investigation.

Fetal and maternal cardiac responses to physical activity and exercise during pregnancy

Since the 1970s, researchers have studied the influence of exercise during pregnancy on offspring heart development. With the knowledge and current evidence of fetal programming effects, research has demonstrated that exercise is safe and beneficial for mother, fetus, and neonate. Predominantly, research has focused on maternal and fetal cardiac adaptations related to aerobic exercise during pregnancy; less is known regarding the effects of resistance or combination (aerobic and resistance) training during pregnancy. Ongoing research is focusing on fetal responses to different intensity, duration and modes of maternal exercise throughout pregnancy. This article will summarize our current state of knowledge regarding the influence of exercise intensity, duration, and modes during pregnancy on maternal and fetal cardiac responses.

Pregnancy distress gets under fetal skin: Maternal ambulatory assessment & sex differences in prenatal development

Prenatal maternal distress is associated with an at-risk developmental profile, yet there is little fetal evidence of this putative in utero process. Moreover, the biological transmission for these maternal effects remains uncertain. In a study of n = 125 pregnant adolescents (ages 14-19), ambulatory assessments of daily negative mood (anger, frustration, irritation, stress), physical activity, blood pressure, heart rate (every 30 min over 24 hr), and salivary cortisol (six samples) were collected at 13-16, 24-27, 34-37 gestational weeks. Corticotropin-releasing hormone, C-reactive protein, and interleukin 6 from blood draws and 20 min assessments of fetal heart rate (FHR) and movement were acquired at the latter two sessions. On average, fetuses showed development in the expected direction (decrease in FHR, increase in SD of FHR and in the correlation of movement and FHR ("coupling")). Maternal distress characteristics were associated with variations in the level and trajectory of fetal measures, and results often differed by sex. For males, greater maternal 1st and 2nd session negative mood and 2nd session physical activity were associated with lower overall FHR (p < .01), while 1st session cortisol was associated with a smaller increase in coupling (p < .01), and overall higher levels (p = .05)-findings suggesting accelerated development. For females, negative mood, cortisol, and diastolic blood pressure were associated with indications of relatively less advanced and accelerated outcomes. There were no associations between negative mood and biological variables. These data indicate that maternal psychobiological status influences fetal development, with females possibly more variously responsive to different exposures.

Maternal stress, nutrition and physical activity: Impact on immune function, CNS development and psychopathology

Evidence suggests that maternal and fetal immune dysfunction may impact fetal brain development and could play a role in neurodevelopmental disorders, although the definitive pathophysiological mechanisms are still not completely understood. Stress, malnutrition and physical inactivity are three maternal behavioral lifestyle factors that can influence immune and central nervous system (CNS) functions in both the mother and fetus, and may therefore, increase risk for neurodevelopmental/psychiatric disorders. First, we will briefly review some aspects of maternal-fetal immune system interactions and development of immune tolerance. Second, we will discuss the bidirectional communication between the immune system and CNS and the pathways by which immune dysfunction could contribute to neurodevelopmental disorders. Third, we will discuss the effects of prenatal stress and malnutrition (over and undernutrition) on perinatal programming of the CNS and immune system, and how this might influence neurodevelopment. Finally, we will discuss the beneficial impact of physical fitness during pregnancy on the maternal-fetal unit and infant and how regular physical activity and exercise can be an effective buffer against stress- and inflammatory-related disorders. Although regular physical activity has been shown to promote neuroplasticity and an anti-inflammatory state in the adult, there is a paucity of studies evaluating its impact on CNS and immune function during pregnancy. Implementing stress reduction, proper nutrition and ample physical activity during pregnancy and the childbearing period may be an efficient strategy to counteract the impact of maternal stress and malnutrition/obesity on the developing fetus. Such behavioral interventions could have an impact on early development of the CNS and immune system and contribute to the prevention of neurodevelopmental and psychiatric disorders. Further research is needed to elucidate this relationship and the underlying mechanisms of protection. This article is part of a Special Issue entitled SI: Neuroimmunology in Health And Disease.

Aerobic exercise during pregnancy and presence of fetal-maternal heart rate synchronization

It has been shown that short-term direct interaction between maternal and fetal heart rates may take place and that this interaction is affected by the rate of maternal respiration. The aim of this study was to determine the effect of maternal aerobic exercise during pregnancy on the occurrence of fetal-maternal heart rate synchronization.

Aerobic exercise during pregnancy influences infant heart rate variability at one month of age

BACKGROUND

Previously, we reported that regular maternal aerobic exercise during pregnancy was associated with lower fetal heart rate (HR) and higher heart rate variability (HRV) at 36weeks gestation. We now report the effect of maternal exercise on infant HR and HRV in subjects who remained active in the study at the one-month follow up visit.

AIMS

We aimed to determine whether differences in fetal cardiac autonomic control related to maternal physical activity were an in utero phenomenon or would persist 1month after birth.

STUDY DESIGN

Magnetocardiograms (MCGs) of infants born to regularly exercising (≥30min of aerobic activity, 3 times per week; N=16) and non-exercising (N=27) pregnant women were recorded using a fetal biomagnetometer. Normal R-peaks were marked to derive infant HR and HRV in time and frequency domains, including the root mean square of successive differences (RMSSD), the standard deviation of normal-to-normal interbeat intervals (SDNN), and power in the low frequency (LF) and high frequency (HF) bands. Group differences were examined with Student's t-tests.

RESULTS

Infants born to exercising women had significantly higher RMSSD (P=0.010), LF power (P=0.002), and HF power (P=0.004) than those born to women who did not engage in regular physical activity while pregnant.

CONCLUSION

Infants born to women who participated in regular physical activity during pregnancy continued to have higher HRV in the infant period. This suggests that the developing cardiac autonomic nervous system is sensitive to the effects of maternal physical activity and is a target for fetal programming.

Differences in the sleep states of IUGR and low-risk fetuses: An MCG study

BACKGROUND

Intrauterine growth restriction (IUGR) is a fetal condition characterized by growth-rate reduction. Afflicted fetuses tend to display abnormalities in heart rate.

OBJECTIVE

To study the differences in the heart-rate variability of low-risk fetuses and IUGR fetuses during different behavioral states.

METHODS

A total of 40 fetal magnetocardiograms were analyzed from 20 low-risk and 20 IUGR fetuses recorded using a 151-sensor SQUID-array system. The maternal cardiac signals were attenuated using signal-space projection. Fetal R waves were identified using an adaptive Hilbert transform approach and fetal heart rate was calculated. In each three-minute window, the heart rate was classified into patterns reflective of quiet sleep (pattern A) and active sleep (pattern B) using the criteria of Nijhuis. Two adjacent 3-min windows exhibiting the same pattern were selected for analysis from every dataset. Heart-rate variability in that 6-min window was characterized using three measures, standard deviation of normal to normal (SDNN), root mean square of successive differences (RMSSD) and phase plane area (PPA).

RESULTS

All three measures tended to be lower in the IUGR group compared to the low-risk group. However, when the measures were analyzed in patterns, only PPA showed significant difference between the risk groups in pattern A, whereas both PPA and SDNN showed highly significant risk-group differences in pattern B. RMSSD did not show any significant risk-group difference.

CONCLUSION

The result signifies that the heart-rate variability of IUGR fetuses is different from that of low-risk fetuses, and only PPA was able to capture the HRV differences in both quiet and active states. The difference between these two groups of fetuses shows that the fetal-activity states are potential confounders when characterizing heart-rate variability.

Benefits of exercise during pregnancy

There is a direct link between healthy mothers and healthy infants. Exercise and appropriate nutrition are important contributors to maternal physical and psychological health. The benefits and potential risks of exercise during pregnancy have gained even more attention, with a number of studies having been published after the 2002 American College of Obstetrics and Gynecologists guidelines. A review of the literature was conducted by using PubMed, Scopus, and Embase to assess the literature regarding the benefits of exercise during pregnancy. The search revealed 219 publications, which the authors then narrowed to 125 publications. The purpose of this review is to briefly summarize the known benefits of exercise to the mother, fetus, and newborn.

Cardiorespiratory coupling in health and disease

Cardiac and respiratory activities are intricately linked both functionally as well as anatomically through highly overlapping brainstem networks controlling these autonomic physiologies that are essential for survival. Cardiorespiratory coupling (CRC) has many potential benefits creating synergies that promote healthy physiology. However, when such coupling deteriorates autonomic dysautonomia may ensue. Unfortunately there is still an incomplete mechanistic understanding of both normal and pathophysiological interactions that respectively give rise to CRC and cardiorespiratory dysautonomia. Moreover, there is also a need for better quantitative methods to assess CRC. This review addresses the current understanding of CRC by discussing: (1) the neurobiological basis of respiratory sinus arrhythmia (RSA); (2) various disease states involving cardiorespiratory dysautonomia; and (3) methodologies measuring heart rate variability and RSA.