Maternal physical activity mode and fetal heart outcome

A narrative review of exercise dose during pregnancy

The current recommendations for prenatal exercise dose align with those from the American College of Sports Medicine; 150 min of moderate intensity every week of pregnancy. However, recent works suggest there may be a dose-dependent beneficial effect for mother and offspring; maternal and offspring health outcomes respond differently to low, medium, and high doses of prenatal exercise. It is, therefore, our aim to summarize the published evidence (years 1950-2023) for five metrics of prenatal exercise training commonly reported, that is, "FITT-V": Frequency (number of sessions), Intensity (metabolic equivalents "METs"), Time (duration of sessions), Type (exercise mode), Volume (exercise MET*mins). The target audience includes clinicians and health care professionals, as well as exercise professionals and physiologists. Data suggest that moderate exercise frequency (3-4 times weekly) appears safe and efficacious for mother and offspring, while there is contradictory evidence for the safety and further benefit of increased frequency beyond 5 sessions per week. Moderate (3-6 METs) and vigorous (>6 METs) intensity prenatal exercise have been shown to promote maternal and offspring health, while little research has been performed on low-intensity (<3 METs) exercise. Exercise sessions lasting less than 1 hr are safe for mother and fetus, while longer-duration exercise should be carefully considered and monitored. Taken together, aerobic, resistance, or a combination of exercise types is well tolerated at medium-to-high volumes and offers a variety of type-specific benefits. Still, research is needed to define (1) the "minimum" effective dose of exercise for mother and offspring health, as well as (2) the maximum tolerable dose from which more benefits may be seen. Additionally, there is a lack of randomized controlled trials addressing exercise doses during the three trimesters of pregnancy. Further, the protocols adopted in research studies should be more standardized and tested for efficacy in different populations of gravid women.

Monitoring one heart to help two: heart rate variability and resting heart rate using wearable technology in active women across the perinatal period

BACKGROUND

Characterizing normal heart rate variability (HRV) and resting heart rate (RHR) in healthy women over the course of a pregnancy allows for further investigation into disease states, as pregnancy is the ideal time period for these explorations due to known decreases in cardiovascular health. To our knowledge, this is the first study to continuously monitor HRV and RHR using wearable technology in healthy pregnant women.

METHODS

A total of 18 healthy women participated in a prospective cohort study of HRV and RHR while wearing a WHOOP® strap prior to conception, throughout pregnancy, and into postpartum. The study lasted from March 2019 to July 2021; data were analyzed using linear mixed models with splines for non-linear trends.

RESULTS

Eighteen women were followed for an average of 405.8 days (SD = 153). Minutes of logged daily activity decreased from 28 minutes pre-pregnancy to 14 minutes by third trimester. A steady decrease in daily HRV and increase in daily RHR were generally seen during pregnancy (HRV Est. = - 0.10, P < 0.0001; RHR Est. = 0.05, P < 0.0001). The effect was moderated by activity minutes for both HRV and RHR. However, at 49 days prior to birth there was a reversal of these indices with a steady increase in daily HRV (Est. = 0.38, P < 0.0001) and decrease in daily RHR (Est. = - 0.23, P < 0.0001), regardless of activity level, that continued into the postpartum period.

CONCLUSIONS

In healthy women, there were significant changes to HRV and RHR throughout pregnancy, including a rapid improvement in cardiovascular health prior to birth that was not otherwise known. Physical activity minutes of any type moderated the known negative consequences of pregnancy on cardiovascular health. By establishing normal changes using daily data, future research can now evaluate disease states as well as physical activity interventions during pregnancy and their impact on cardiovascular fitness.

Maternal Obesity: A Focus on Maternal Interventions to Improve Health of Offspring

Maternal obesity has many implications for offspring health that persist throughout their lifespan that include obesity and cardiovascular complications. Several different factors contribute to obesity and they encompass interplay between genetics and environment. In the prenatal period, untreated obesity establishes a foundation for a myriad of symptoms and negative delivery experiences, including gestational hypertensive disorders, gestational diabetes, macrosomia, and labor complications. However, data across human and animal studies show promise that nutritional interventions and physical activity may rescue much of the adverse effects of obesity on offspring metabolic health. Further, these maternal interventions improve the health of the offspring by reducing weight gain, cardiovascular disorders, and improving glucose tolerance. Mechanisms from animal studies have also been proposed to elucidate the signaling pathways that regulate inflammation, lipid metabolism, and oxidative capacity of the tissue, ultimately providing potential specific courses of treatment. This review aims to pinpoint the risks of maternal obesity and provide plausible intervention strategies. We delve into recent research involving both animal and human studies with maternal interventions. With the increasing concerning of obesity rates witnessed in the United States, it is imperative to acknowledge the long-term effects posed on future generations and specifically modify maternal nutrition and care to mitigate these adverse outcomes.

High physical activity and high sedentary behavior increased the risk of gestational diabetes mellitus among women with excessive gestational weight gain: a prospective study

Background

Although physical activity (PA) in pregnancy benefits most women, not much is known about pregnancy-related changes in PA and its association with gestational diabetes mellitus (GDM) risk. The aim of this study was to identify the trajectory of PA during pregnancy and possible associations with the risk of GDM.

Methods

This was a prospective cohort study of 452 pregnant women recruited from 3 health clinics in a southern state of Peninsular Malaysia. PA levels at the first, second, and third trimester were assessed using the Pregnancy Physical Activity Questionnaire. GDM was diagnosed at 24–28 weeks of gestation following the Ministry of Health Malaysia criteria. Group-based trajectory modeling was used to identify PA trajectories. Three multivariate logistic models were used to estimate the odds of trajectory group membership and GDM.

Results

Two distinct PA trajectories were identified: low PA levels in all intensity of PA and sedentary behavior (Group 1: 61.1%, n = 276) and high PA levels in all intensity of PA as well as sedentary behavior (Group 2: 38.9%, n = 176). Moderate and high intensity PA decreased over the course of pregnancy in both groups. Women in group 2 had significantly higher risk of GDM in two of the estimated logistic models. In all models, significant associations between PA trajectories and GDM were only observed among women with excessive gestational weight gain in the second trimester.

Conclusions

Women with high sedentary behavior were significantly at higher risk of GDM despite high PA levels by intensity and this association was significant only among women with excessive GWG in the second trimester. Participation in high sedentary behavior may outweigh the benefit of engaging in high PA to mitigate the risk of GDM.

Maternal physical activity significantly alters the placental transcriptome

INTRODUCTION

Maternal lifestyle, in particular physical activity (PA), influences many of the physiological adaptations during pregnancy associated with feto-placental development and growth. There is limited to no information on the link between PA during pregnancy and the molecular mechanisms governing placental function. The aim of this study was to investigate the molecular mechanisms through which maternal PA may influence placental function.

METHODS

The level of PA was measured by accelerometry and gene expression was measured in term placenta with custom polymerase chain reaction (PCR) arrays and microarray analysis followed by a pathway analyses on significantly differentially expressed genes (DEGs).

RESULTS

Microarray analysis showed 43 significantly DEGs between active and non-active participants. RT-qPCR validation of a sub-sample of DEGs revealed significant changes in the level of expression between active and non-active moms (student's t-test, p < 0.05, n = 11). Genes involved in transport of water (p = 0.00236) and uptake of glycerol (p = 0.00219) were enriched in active moms. PA was also associated with the alteration of alternative splicing patters. The most consistent splicing changes were observed for AQP9 where active moms lacked exon 2.

DISCUSSION

Variations in maternal PA influences placental gene. We show significant expression changes of genes that are involved in transport and localization between active and non-active women. Most notably, the expression of the aquaporin family of genes (e.g. AQP1 and AQP9) were found to be significantly higher in the placentas of active women suggesting an adaptive response for the transport of water and glycerol in this population.

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.

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.

Effects of prenatal exercise on fetal heart rate, umbilical and uterine blood flow: a systematic review and meta-analysis

OBJECTIVE

To perform a systematic review and meta-analysis examining the influence of acute and chronic prenatal exercise on fetal heart rate (FHR) and umbilical and uterine blood flow metrics.

DESIGN

Systematic review with random-effects meta-analysis and meta-regression.

DATA SOURCES

Online databases were searched up to 6 January 2017.

STUDY ELIGIBILITY CRITERIA

Studies of all designs were included (except case studies) if published in English, Spanish or French, and contained information on the population (pregnant women without contraindication to exercise), intervention (subjective or objective measures of frequency, intensity, duration, volume or type of exercise, alone ["exercise-only"] or in combination with other intervention components [eg, dietary; "exercise + co-intervention"]), comparator (no exercise or different frequency, intensity, duration, volume and type of exercise) and outcomes (FHR, beats per minute (bpm); uterine and umbilical blood flow metrics (systolic:diastolic (S/D) ratio; Pulsatility Index (PI); Resistance Index (RI); blood flow, mL/min; and blood velocity, cm/s)).

RESULTS

'Very low' to 'moderate' quality evidence from 91 unique studies (n=4641 women) were included. Overall, FHR increased during (mean difference (MD)=6.35bpm; 95% CI 2.30 to 10.41, I²=95%, p=0.002) and following acute exercise (MD=4.05; 95% CI 2.98 to 5.12, I²=83%, p<0.00001). The incidence of fetal bradycardia was low at rest and unchanged with acute exercise. There were no significant changes in umbilical or uterine S/D, PI, RI, blood flow or blood velocity during or following acute exercise sessions. Chronic exercise decreased resting FHR and the umbilical artery S/D, PI and RI at rest.

CONCLUSION

Acute and chronic prenatal exercise do not adversely impact FHR or uteroplacental blood flow metrics.

Influence of maternal exercise on fetal heart response during labor and delivery

OBJECTIVES

The purpose of this study was to determine if prenatal exercise alters the maternal and fetal heart responses during labor and delivery. We hypothesized that fetuses of exercising mothers would exhibit a lower baseline heart rate (HR), increased HR variability (HRV), and no differences in fetal heart accelerations and decelerations.

DESIGN

This study employed a cross-sectional design.

METHODS

The Modifiable Physical Activity Questionnaire was used for group classification. Exercising women were those participating in 30 minutes of moderate-to-vigorous exercise at least 3×/week throughout the entire pregnancy. Women achieving a lower dose of exercise were classified as non-exercisers. Cardiotocography recordings during the first hour of labor and delivery assessed fetal baseline HR, HRV, accelerations, decelerations, and contractions. ANCOVA analyses were performed to assess group differences in these outcomes and were adjusted for maternal body mass index.

RESULTS

Thirty-one women were included in the analyses. No group mean differences were found for maternal and fetal characteristics, except for maternal age (EX: mean (SD) 28.5 (±4.6y) vs NON-EX: 24.1 (±1.2y)). After controlling for body mass index, no statistical differences in maternal HR response (β = 3.9, SE = 5.0, 95%CI -6.4-14.2) or fetal HR response (β = 3.9, SE = 2.5, 95%CI -1.2-9.11), accelerations and decelerations (β= -0.03, SE = 0.4, 95%CI -0.9-0.8; β= -0.10, SE = 0.4, 95%CI -0.8-0.9, respectively), or HRV (β = 0.6, SE = 1.7, 95%CI -2.8-4.0) were observed.

CONCLUSIONS

Based on the findings of this study, we found no evidence that maternal exercise during pregnancy was associated with maternal or fetal HR response during labor and delivery. These data suggest maternal exercise may not elicit positive or negative effects on maternal and fetal cardiovascular responses to the physiological stress of labor and delivery.

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).

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.

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.

Effects of Exercise During Pregnancy on Maternal Heart Rate and Heart Rate Variability

BACKGROUND

Pregnancy is associated with an increased sympathetic state, which can be exacerbated by gestational conditions. Research has shown that exercise during pregnancy lowers heart rate (HR) and can attenuate the symptoms of gestational conditions associated with increased sympathetic control. However, changes in maternal heart autonomic function in response to exercise have not been reported across multiple time points during pregnancy. This analysis is designed to address this gap.

OBJECTIVE

To determine if exercise throughout gestation improves maternal cardiac autonomic nervous system functioning, as evidenced by decreased HR and increased heart rate variability (HRV) indices.

DESIGN

Case control study.

SETTING

Academic medical institution.

PARTICIPANTS

A total of 56 women with healthy, singleton, low-risk pregnancies.

METHODS

Participants were asked to complete 3 resting 18-minute HRV recordings at 28, 32, and 36 weeks' gestation, along with a physical activity questionnaire.

MAIN OUTCOME MEASURES

HRV indices were calculated for time (R peak to R peak interval standard deviation and root mean squared of successive differences) and frequency (very low, low, and high frequency) domain measures. The differences between groups were compared for HRV indices at 28, 32, and 36 weeks.

RESULTS

Resting HR was significantly lower in the exercise group at 28 weeks (P < .01) compared with the control group. The exercise group had significantly (P < .05) increased measures of resting HRV time domain measures at 28, 32, and 36 weeks' gestation compared with the control group. Resting HRV power was significantly increased (P < .05) in all frequency domain measures at 32 weeks in the exercise group relative to the control group. No differences occurred in sympathovagal balance (low frequency/high frequency ratio) between groups.

CONCLUSION

Exercise throughout pregnancy can significantly improve cardiac autonomic control. More research is needed to determine if this adaptation to exercise may reduce the risk of adverse outcomes associated with gestational conditions with poor autonomic control, such as diabetes, hypertension, pre-eclampsia, and excessive weight gain.

Toward the improvement in fetal monitoring during labor with the inclusion of maternal heart rate analysis

Fetal heart rate (FHR) monitoring is used routinely in labor, but conventional methods have a limited capacity to detect fetal hypoxia/acidosis. An exploratory study was performed on the simultaneous assessment of maternal heart rate (MHR) and FHR variability, to evaluate their evolution during labor and their capacity to detect newborn acidemia. MHR and FHR were simultaneously recorded in 51 singleton term pregnancies during the last two hours of labor and compared with newborn umbilical artery blood (UAB) pH. Linear/nonlinear indices were computed separately for MHR and FHR. Interaction between MHR and FHR was quantified through the same indices on FHR-MHR and through their correlation and cross-entropy. Univariate and bivariate statistical analysis included nonparametric confidence intervals and statistical tests, receiver operating characteristic curves and linear discriminant analysis. Progression of labor was associated with a significant increase in most MHR and FHR linear indices, whereas entropy indices decreased. FHR alone and in combination with MHR as FHR-MHR evidenced the highest auROC values for prediction of fetal acidemia, with 0.76 and 0.88 for the UAB pH thresholds 7.20 and 7.15, respectively. The inclusion of MHR on bivariate analysis achieved sensitivity and specificity values of nearly 100 and 89.1%, respectively. These results suggest that simultaneous analysis of MHR and FHR may improve the identification of fetal acidemia compared with FHR alone, namely during the last hour of labor.

Influence of exercise mode on pregnancy outcomes: ENHANCED by Mom project

Background

The extent of the benefits of exercise training during pregnancy on maternal, fetal, and neonatal health outcomes has not been sufficiently addressed. While aerobic exercise training has been determined as safe and efficacious throughout pregnancy, the effects of other training modes on fetal health and development as well as any continued benefits for the neonate, especially with regards to cardiovascular development and function, is largely unknown. In the ENHANCED by Mom study we aim to determine the effects of different modes of exercise training (aerobic, circuit, and resistance) throughout pregnancy on childhood health by controlling individual exercise programs and assessing the effects of each on fetal and neonatal health adaptations.

Methods/Design

ENHANCED by mom is a cross sectional comparison study utilizing 3 intervention groups in comparison to a control group. Participants will complete three 5 min warmup + 45 min sessions weekly from 16 weeks to 36 weeks gestation of aerobic, resistance, or circuit training, in comparison to non-exercising controls. Maternal physical measurements will occur every 4 weeks throughout the intervention period. Fetal morphometric and heart measurements will occur at 34 weeks gestation. Neonatal measurements will be acquired at birth and at 1 month, 6 months, and 12 months.

Discussion

A better understanding on the effects of exercise training during pregnancy on fetal and neonatal health could have a profound impact on the prevention and development of chronic diseases such as obesity, hypertension, and diabetes.