The Impact of Exercise Training on Muscle Sympathetic Nerve Activity: A Systematic Review and Meta-Analysis.

The purpose of this systematic review and meta-analysis was to examine the effects of exercise training on muscle sympathetic nerve activity (MSNA) in humans. Studies included exercise interventions (randomized controlled trials [RCTs], non-randomized controlled trials [non-RCTs] or pre-to-post intervention) that reported on adults (>18 years) where MSNA was directly assessed using microneurography, and relevant outcomes were assessed (MSNA [total activity, burst frequency, burst incidence, amplitude], heart rate, blood pressure [systolic blood pressure, diastolic blood pressure, or mean blood pressure], and aerobic capacity [maximal or peak oxygen consumption]). 40 intervention studies (n=1,253 individuals) were included. RCTs of exercise compared to no exercise illustrated that those randomized to the exercise intervention had a significant reduction in MSNA burst frequency and incidence compared to controls. This reduction in burst frequency was not different between individuals with cardiovascular disease compared to those without. However, the reduction in burst incidence was greater in those with cardiovascular disease (9 RCTs studies, n = 234, MD -21.08 bursts/100 hbs; 95% CI -16.51, -25.66; I2 = 63%) compared to those without (6 RCTs, n = 192, MD -10.92 bursts/100 hbs; 95% CI -4.12, -17.73; I2 = 76%). Meta-regression analyses demonstrated a dose-response relationship where individuals with higher burst frequency and incidence pre-intervention had a greater reduction in values post-intervention. These findings suggest that exercise training reduces muscle sympathetic nerve activity, which may be valuable for improving cardiovascular health.

The effect of hyperoxia on muscle sympathetic nerve activity: a systematic review and meta-analysis.

PURPOSE: We conducted a meta-analysis to determine the effect of hyperoxia on muscle sympathetic nerve activity in healthy individuals and those with cardio-metabolic diseases. METHODS: A comprehensive search of electronic databases was performed until August 2022. All study designs (except reviews) were included: population (humans; apparently healthy or with at least one chronic disease); exposures (muscle sympathetic nerve activity during hyperoxia or hyperbaria); comparators (hyperoxia or hyperbaria vs. normoxia); and outcomes (muscle sympathetic nerve activity, heart rate, blood pressure, minute ventilation). Forty-nine studies were ultimately included in the meta-analysis. RESULTS: In healthy individuals, hyperoxia had no effect on sympathetic burst frequency (mean difference [MD] - 1.07 bursts/min; 95% confidence interval [CI] - 2.17, 0.04bursts/min; P = 0.06), burst incidence (MD 0.27 bursts/100 heartbeats [hb]; 95% CI - 2.10, 2.64 bursts/100 hb; P = 0.82), burst amplitude (P = 0.85), or total activity (P = 0.31). In those with chronic diseases, hyperoxia decreased burst frequency (MD - 5.57 bursts/min; 95% CI - 7.48, - 3.67 bursts/min; P < 0.001) and burst incidence (MD - 4.44 bursts/100 hb; 95% CI - 7.94, - 0.94 bursts/100 hb; P = 0.01), but had no effect on burst amplitude (P = 0.36) or total activity (P = 0.90). Our meta-regression analyses identified an inverse relationship between normoxic burst frequency and change in burst frequency with hyperoxia. In both groups, hyperoxia decreased heart rate but had no effect on any measure of blood pressure. CONCLUSION: Hyperoxia does not change sympathetic activity in healthy humans. Conversely, in those with chronic diseases, hyperoxia decreases sympathetic activity. Regardless of disease status, resting sympathetic burst frequency predicts the degree of change in burst frequency, with larger decreases for those with higher resting activity.

Guidelines for Assessing Maternal Cardiovascular Physiology During Pregnancy and Postpartum.

Maternal mortality rates are at an all-time high across the world and are set to increase in subsequent years. Cardiovascular disease is the leading cause of death during pregnancy and postpartum, especially in the US. Therefore, understanding the physiological changes in the cardiovascular system during normal pregnancy is necessary to understand disease-related pathology. Significant systemic and cardiovascular physiological changes occur during pregnancy that are essential for supporting the maternal-fetal dyad. The physiological impact of pregnancy on the cardiovascular system has been examined in both experimental animal models and in humans. However, there is a continued need in this field of study to provide increased rigor and reproducibility. Therefore, these guidelines aim to provide information regarding best practices and recommendations to accurately and rigorously measure cardiovascular physiology during normal and cardiovascular-disease-complicated pregnancies in human and animal models.

"Is It Realistic?": A Qualitative Study of the Experiences of Elite Women Athletes Considering Parenthood.

BACKGROUND AND OBJECTIVE: As the visibility and acceptance of athlete-mothers increase, so does the number of women athletes considering parenthood. Yet, many athletes struggle with the decision to become a parent while competing at the elite level due to the significant changes and uncertainties that have been reported by pregnant and parenting athletes. The experiences of women athletes considering parenthood are under-represented in the vast sport literature but are necessary for developing evidenced-based policies and practices that can support women's equitable participation in high-performance sport contexts. Thus, the purpose of this qualitative study was to describe the experiences of elite women athletes that are considering parenthood. METHODS: Participants were ten elite North American athletes (29-36 years) who are considering becoming parents in the next 5 years. Each participant self-identified as a woman and competed at the highest level in their respective sport. Data were generated via one-on-one semi-structured interviews that were audio-recorded, transcribed verbatim, and analyzed through a process of content analysis. RESULTS: The experiences of elite women athletes considering parenthood are represented by five themes: (a) calls for essential mandates and leadership, (b) how do you support yourself?, (c) hesitation of body changes, (d) age inequities, and (e) being proactive about reproductive health. Such findings support an in-depth understanding of gender-specific stressors that limit women's equitable participation in high-performance contexts. CONCLUSION: This research is grounded in the voices of elite women athletes and identifies actionable steps necessary for research and culture change. Findings provide necessary evidence to inform the development of sport policies to support those athletes that are considering becoming parents.

Translation and cross-cultural adaptation of the Get Active Questionnaire for Pregnancy (kwestionariusz "Badz Aktywna w Ciazy") to support physical activity among pregnant women in Poland.

INTRODUCTION: Physical activity during pregnancy is established to derive clinically meaningful improvements in pregnancy, childbirth, and postpartum health outcomes. Evidence-based pre-screening tools have been developed to support the implementation of physical activity programmes, and enhance communication between health care providers, exercise professionals and pregnant women. The Get Active Questionnaire for Pregnancy (GAQ-P) and the Health Care Provider Consultation Form for Prenatal Physical Activity (HCPCF) empower pregnant women to identify whether they require additional counselling from their obstetric health care provider in terms of physical activity. However, these tools are not available in Polish. This work details the process taken to translate the GAQ-P and HCPCF into Polish. MATERIAL AND METHODS: We followed the translation process outlined by the Translation and Cultural Adaptation International Society for Pharmacoeconomics and Outcomes Research (ISPOR) guidelines between August 2022 and August 2023. We formed an expert group that included representatives of the Polish Society of Sports Medicine, The Polish Society of Gynaecologists and Obstetricians, practitioners, and scientists in physical activity during pregnancy. We implemented 9 of the 10 steps recommended by ISOPR in the translation process. At the Cognitive Debriefing stage, we collected opinions on the Polish version of GAQ-P and HCPCF from 70 stakeholders on the clarity and cultural appropriateness of the translation. RESULTS AND CONCLUSIONS: Target users have positively evaluated the Polish version of GAQ-P and HCPCF. Thanks to the ISPOR methodology, we obtained a trustworthy, evidence-based screening tools, which can reduce the barriers for most women to be physically active during pregnancy.

Clinical and exercise professional opinion on designing a postpartum return-to-running training programme: an international Delphi study and consensus statement.

Returning to running postpartum presents challenges such as musculoskeletal pain and pelvic floor dysfunction for some females, but there is little guidance on developing and progressing postpartum training programmes. This study aims to establish expert consensus recommendations on designing and modifying a postpartum return-to-running training programme, highlight costs and access to qualified professionals as potential barriers and discuss clinical, research and sports policy implications.A three-round Delphi survey of clinical and exercise professionals working with postpartum runners was conducted. Round I consisted of open-ended questions related to designing the training plan, modifications based on biopsychosocial factors, key muscle groups to train and referral and payment sources. Rounds II and III involved Likert-scale voting to identify consensus (≥75% agreement).118 participants completed Round I, 107 completed Round II (response rate 90.6%) and 95 completed Round III (response rate 80.5%). Consensus was reached in 42/47 (89%) statements, including recommendations for a period of relative rest, gradual increases in duration and intensity, starting with a walk-run protocol and incorporating strength training. Training should be modified based on musculoskeletal or pelvic symptoms, sleep, mental health, lactation or energy availability concerns. Cost and access to experienced postpartum running professionals were identified as potential barriers for runners to receive care.Consensus recommendations for a postpartum return-to-running programme include an individualised exercise prescription, gradual increases in physical activity, walk-run protocols and targeted muscle strengthening. Further research and improved access to clinical and exercise professionals are needed to inform and facilitate best practices.

Clinical and exercise professional opinion of return-to-running readiness after childbirth: an international Delphi study and consensus statement.

Female athletes have identified a lack of guidance as a barrier to successfully returning to running postpartum, and existing guidelines are vague. Our aim was to define the current practice of determining postpartum run-readiness through a consensus survey of international clinicians and exercise professionals in postpartum exercise to assist clinicians and inform sport policy changes.A three-round Delphi approach was used to gain international consensus from clinicians and exercise professionals on run-readiness postpartum. Professionals who work with postpartum runners participated in an online survey to answer open-ended questions about the following postpartum return-to-running topics: definitions (runner and postpartum), key biopsychosocial milestones that runners need to meet, recommended screening, timeline to initiate running, support items, education topics and factors that contribute to advising against running. Consensus was defined as ≥75% participant agreement.One hundred and eighteen professionals participated in round I, 107 participated in round II (response rate 90.6%) and 95 participated in round III (response rate 80.5%). Responses indicated that, following a minimum 3-week period of rest and recovery, an individualised timeline and gradual return to running progression can be considered. Screening for medical and psychological concerns, current physical capacity, and prior training history is recommended prior to a return to running.This study proposes recommendations for the initial guidance on return-to-running postpartum, framed in the context of current research and consensus from professionals. Future research is needed to strengthen and validate specific recommendations and develop guidelines for best practice when returning-to-running after childbirth.

Filling the evidence void: exploration of coach and healthcare provider experiences working with pregnant and postpartum elite athletes - a qualitative study.

OBJECTIVE: Recent research grounded in the experiences of elite female athletes has shed light on the complex challenges of navigating sport environments that do not support or value pregnant or postpartum athletes. The purpose of this study was to explore the unique experiences of coaches and healthcare providers working with pregnant and postpartum elite athletes, and to identify actionable steps for research, policy and culture change to support them. METHODS: Sixteen participants (five coaches, three physicians and eight physiotherapists), who have worked with pregnant and/or postpartum elite athletes within the last 5 years, participated in this qualitative study. Thirteen participants self-identified as women, and three as men. Data were generated via semistructured one-on-one interviews that were audiorecorded, transcribed verbatim and analysed through a process of content analysis. RESULTS: The findings of this research are represented by five main themes: (a) lack of female athlete reproductive research, (b) need for evidence-informed education and training, (c) need to develop evidence-based progression for sport participation in pregnancy and postpartum, (d) open communication to support athlete-centred care and (e) essential supports and changes required for pregnant/postpartum athletes. CONCLUSION: Findings from this study, which are grounded in the unique perspectives of coaches and healthcare providers, outline specific recommendations to inform policy and practices that support athletes through the perinatal period, such as developing evidence-based return-to-sport protocols.

The effect of hypoxemia on muscle sympathetic nerve activity and cardiovascular function: a systematic review and meta-analysis.

We conducted a systematic review and meta-analysis to determine the effect of acute poikilocapnic, high-altitude, and acute isocapnia hypoxemia on muscle sympathetic nerve activity (MSNA) and cardiovascular function. A comprehensive search across electronic databases was performed until June 2021. All observational designs were included: population (healthy individuals); exposures (MSNA during hypoxemia); comparators (hypoxemia severity and duration); outcomes (MSNA; heart rate, HR; and mean arterial pressure, MAP). Sixty-one studies were included in the meta-analysis. MSNA burst frequency increased by a greater extent during high-altitude hypoxemia [P < 0.001; mean difference (MD), +22.5 bursts/min; confidence interval (CI) = -19.20 to 25.84] compared with acute poikilocapnic hypoxemia (P < 0.001; MD, +5.63 bursts/min; CI = -4.09 to 7.17) and isocapnic hypoxemia (P < 0.001; MD, +4.72 bursts/min; CI = -3.37 to 6.07). MSNA burst amplitude was only elevated during acute isocapnic hypoxemia (P = 0.03; standard MD, +0.46 au; CI = -0.03 to 0.90), and MSNA burst incidence was only elevated during high-altitude hypoxemia [P < 0.001; MD, 33.05 bursts/100 heartbeats; CI = -28.59 to 37.51]. Meta-regression analysis indicated a strong relationship between MSNA burst frequency and hypoxemia severity for acute isocapnic studies (P < 0.001) but not acute poikilocapnia (P = 0.098). HR increased by the same extent across each type of hypoxemia [P < 0.001; MD +13.81 heartbeats/min; 95% CI = 12.59-15.03]. MAP increased during high-altitude hypoxemia (P < 0.001; MD, +5.06 mmHg; CI = 3.14-6.99), and acute isocapnic hypoxemia (P < 0.001; MD, +1.91 mmHg; CI = 0.84-2.97), but not during acute poikilocapnic hypoxemia (P = 0.95). Both hypoxemia type and severity influenced sympathetic nerve and cardiovascular function. These data are important for the better understanding of healthy human adaptation to hypoxemia.

Increased stiffness of omental arteries from late pregnant women at advanced maternal age.

Advanced maternal age (≥35 years) is a risk factor for poor pregnancy outcomes. Pregnancy requires extensive maternal vascular adaptations, and with age, our blood vessels become stiffer and change in structure (collagen and elastin). However, the effect of advanced maternal age on the structure of human resistance arteries during pregnancy is unknown. As omental resistance arteries contribute to blood pressure regulation, assessing their structure in pregnancy may inform on the causal mechanisms underlying pregnancy complications in women of advanced maternal age. Omental fat biopsies were obtained from younger (<35 years) or advanced maternal age (≥35 years) women during caesarean delivery (n = 7-9/group). Arteries (200-300 µm) were isolated and passive mechanical properties (circumferential stress and strain) assessed with pressure myography. Collagen (Masson's Trichrome) and elastin (Verhoff) were visualized histologically and % positively-stained area was assessed. Median maternal age was 32 years (range 25-34) for younger, and 38 years (range 35-42) for women of advanced maternal age. Circumferential strain was lower in arteries from advanced maternal age versus younger women but circumferential stress was not different. Omental artery collagen levels were similar, while elastin levels were lower with advanced maternal age versus younger pregnancies. The collagen:elastin ratio was greater in arteries from advanced maternal age versus younger women. In conclusion, omental arteries from women of advanced maternal age were less compliant with less elastin compared with arteries of younger controls, which may affect how vascular stressors are tolerated during pregnancy. Understanding how vascular aging affects pregnancy adaptations may contribute to better pregnancy outcomes.

Maternal and Fetal Cardiovascular Responses to Acute High-Intensity Interval and Moderate-Intensity Continuous Training Exercise During Pregnancy: A Randomized Crossover Trial.

OBJECTIVE: We aimed to compare maternal and fetal cardiovascular responses to an acute bout of high-intensity interval training (HIIT) versus moderate-intensity continuous training (MICT) during pregnancy. METHODS: Fifteen women with a singleton pregnancy (27.3 ± 3.5 weeks of gestation, 33 ± 4 years of age) were recruited. Following a peak fitness test, participants engaged in a session of HIIT (10 × 1-min intervals ≥ 90% maximum heart rate [HRmax]) interspersed with 1 min of active recovery) and MICT (30 min at 64-76% HRmax) 48 h apart in random order. Maternal HR, blood pressure, middle (MCAv), and posterior cerebral artery blood velocity (PCAv), as well as respiratory measures were monitored continuously throughout HIIT/MICT. Fetal heart rate, as well as umbilical systolic/diastolic (S/D) ratio, resistive index (RI), and pulsatility index (PI) were assessed immediately before and after exercise. RESULTS: Average maternal heart rate was higher for HIIT (82 ± 5% HRmax) compared with MICT (74 ± 4% HRmax; p < 0.001). During the HIIT session, participants achieved a peak heart rate of 96 ± 5% HRmax (range of 87-105% HRmax). Maternal cerebral blood velocities increased with exercise but was not different between HIIT and MICT for MCAv (p = 0.340) and PCAv (p = 0.142). Fetal heart rate increased during exercise (p = 0.244) but was not different between sessions (HIIT: Δ + 14 ± 7 bpm; MICT: Δ + 10 ± 10 bpm). Metrics of umbilical blood flow decreased with exercise and were not different between exercise sessions (PI: p = 0.707; S/D ratio: p = 0.671; RI: p = 0.792). Fetal bradycardia was not observed, and S/D ratio, RI, and PI remained within normal ranges both before and immediately after all exercise sessions. CONCLUSIONS: An acute bout of HIIT exercise consisting of repeated 1-min near-maximal to maximal exertions, as well as MICT exercise is well tolerated by both mother and fetus. CLINICAL TRIAL REGISTRATION: NCT05369247.

Increased respiratory modulation of cardiovascular control reflects improved blood pressure regulation in pregnancy.

Hypertensive pregnancy disorders put the maternal-fetal dyad at risk and are one of the leading causes of morbidity and mortality during pregnancy. Multiple efforts have been made to understand the physiological mechanisms behind changes in blood pressure. Still, to date, no study has focused on analyzing the dynamics of the interactions between the systems involved in blood pressure control. In this work, we aim to address this question by evaluating the phase coherence between different signals using wavelet phase coherence. Electrocardiogram, continuous blood pressure, electrocardiogram-derived respiration, and muscle sympathetic nerve activity signals were obtained from ten normotensive pregnant women, ten normotensive non-pregnant women, and ten pregnant women with preeclampsia during rest and cold pressor test. At rest, normotensive pregnant women showed higher phase coherence in the high-frequency band (0.15-0.4 Hz) between muscle sympathetic nerve activity and the RR interval, blood pressure, and respiration compared to non-pregnant normotensive women. Although normotensive pregnant women showed no phase coherence differences with respect to hypertensive pregnant women at rest, higher phase coherence between the same pairs of variables was found during the cold pressor test. These results suggest that, in addition to the increased sympathetic tone of normotensive pregnant women widely described in the existing literature, there is an increase in cardiac parasympathetic modulation and respiratory-driven modulation of muscle sympathetic nerve activity and blood pressure that could compensate sympathetic increase and make blood pressure control more efficient to maintain it in normal ranges. Moreover, blunted modulation could prevent its buffer effect and produce an increase in blood pressure levels, as observed in the hypertensive women in this study. This initial exploration of cardiorespiratory coupling in pregnancy opens the opportunity to follow up on more in-depth analyses and determine causal influences.

Optimizing Blood Glucose Control through the Timing of Exercise in Pregnant Individuals Diagnosed with Gestational Diabetes Mellitus.

This study aimed to evaluate the effectiveness of moderate intensity walking on postprandial blood glucose control for pregnant individuals with (GDM) and without gestational diabetes mellitus (NON-GDM). Using a randomized cross-over design, individuals completed 5 days of exercise (three 10-min walks immediately after eating (SHORT), or one 30-min walk (LONG) outside of 1 h after eating). These protocols were preceded and separated by 2-days of habitual exercise (NORMAL). Individuals were instrumented with a continuous glucose monitor, a physical activity monitor for 14-days, and a heart rate monitor during exercise. Participants completed a physical activity enjoyment scale (PACES) to indicate their protocol preference. The GDM group had higher fasting, 24-h mean, and daily peak glucose values compared to NON-GDMs across all conditions (effect of group, p = 0.02; p = 0.02; p = 0.03, respectively). Fasting, 24-h mean, and daily peak glucose were not influenced by the SHORT or LONG exercise (effect of intervention, p > 0.05). Blood glucose values were higher among the GDM group for at least 1 h after eating, yet the exercise intervention had no effect on 1 or 2 h postprandial glucose values (effect of intervention, p > 0.05). Physical activity outcomes (wear time, total activity time, and time spent on each intensity) were not different between the groups nor interventions (effect of group, p > 0.05; effect of intervention, p > 0.05,). There were no differences between the groups or interventions for the PACES score (effect of group, p > 0.05; effect of intervention, p > 0.05). To conclude, there were no differences between the groups or exercise protocols on blood glucose control. More research is warranted to elucidate higher exercise volumes in this outcome for individuals with GDM.

Muscle sympathetic nerve activity during pregnancy: A systematic review and meta-analysis.

We conducted a systematic review and meta-analysis to quantify the impact of healthy and complex pregnancy on muscle sympathetic nerve activity (MSNA) at rest, and in response to stress. Structured searches of electronic databases were performed until February 23, 2022. All study designs (except reviews) were included: population (pregnant individuals); exposures (healthy and complicated pregnancy with direct measures of MSNA); comparator (individuals who were not pregnant, or with uncomplicated pregnancy); and outcomes (MSNA, BP, and heart rate). Twenty-seven studies (N = 807) were included. MSNA burst frequency was higher in pregnancy (n = 201) versus non-pregnant controls (n = 194) (Mean Differences [MD], MD: 10.6 bursts/min; 95% CI: 7.2, 14.0; I2  = 72%). Accounting for the normative increase in heart rate with gestation, burst incidence was also higher during pregnancy (Pregnant N = 189, non-pregnant N = 173; MD: 11 bpm; 95% CI: 8, 13 bpm; I2  = 47%; p < 0.0001). Meta-regression analyses confirmed that although sympathetic burst frequency and incidence are augmented during pregnancy, this was not significantly associated with gestational age. Compared to uncomplicated pregnancy, individuals with obesity, obstructive sleep apnea, and gestational hypertension exhibited sympathetic hyperactivity, while individuals with gestational diabetes mellitus or preeclampsia did not. Uncomplicated pregnancies exhibited a lesser response to head-up tilt, but an exaggerated sympathetic responsiveness to cold pressor stress compared to non-pregnant individuals. MSNA is higher in pregnant individuals and further increased with some, but not all pregnancy complications. PROSPERO registration number: CRD42022311590.

Prenatal Exercise and Cardiovascular Health (PEACH) study: impact of meal timing and pre-exercise blood glucose values on glycemic responses to acute exercise in pregnancy.

We retrospectively analyzed data from 28 participants engaging in moderate-intensity aerobic exercise (265 sessions; 25-40 min) between 18-34 weeks gestation (NCT02948439). The mean change in blood glucose (BG) from pre- to post-acute exercise session was -1.0 ± 1.2 mmol/L. Pre-exercise BG significantly predicted the change in BG (p < 0.001), even when controlling for meal timing, exercise duration, and gestational age. Hypoglycemia only occurred in 3% of sessions. Therefore, in healthy pregnancy the change in BG during exercise is small and primarily related to pre-exercise BG values.

Impact of heavy resistance training on pregnancy and postpartum health outcomes.

INTRODUCTION AND HYPOTHESIS: Participation in Olympic weightlifting, the Valsalva maneuver, and acute or prolonged supine weightlifting during pregnancy are cautioned against; however, these recommendations are based on expert opinions as opposed to empirical evidence. The aim of this study was to examine the training and health outcomes of individuals who engaged in heavy resistance training during pregnancy. METHODS: A total of 679 individuals who lifted at least 80% one-repetition maximum during pregnancy participated in an online survey. RESULTS: Participants were primarily recreational athletes (88%, 332 out of 675) engaged in CrossFit™ (61%, 410 out of 675) and/or weightlifting (49%, 332 out of 675) during pregnancy. Most participants reported no complications during pregnancy or delivery (66%, 388 out of 589), whereas 57% (241 out of 426) reported urinary incontinence following pregnancy. Participants who maintained pre-pregnancy training levels until delivery reported significantly less reproductive complications than those who ceased training levels prior to delivery (p = 0.006). Most respondents engaged in Olympic lifting (72%, 311 out of 432) and lifting in a supine position (71%, 306 out of 437), whereas fewer reported use of the Valsalva maneuver during pregnancy (34%, 142 out of 412). Most returned to weightlifting following delivery (89%, 400 out of 447, average: 3.2 ± 3.0 months), including Olympic lifting (81%, 300 out of 372, average: 4.0 ± 3.4 months) and Valsalva (62%, 213 out of 341, average: 4.5 ± 3.6 months). CONCLUSIONS: Individuals who engaged in heavy prenatal resistance training had typical perinatal and pelvic floor health outcomes that were not altered whether they engaged in, or avoided Olympic lifting, Valsalva or supine weightlifting.

The sympathetic nervous system in healthy and hypertensive pregnancies: physiology or pathology?

NEW FINDINGS: What is the topic of this review? Sympathoexcitation in both healthy and hypertensive pregnancies, and concurrent adaptations along the neurovascular cascade. What advances does it highlight? Known and plausible adaptations along the neurovascular cascade which may offset elevated MSNA in normotensive pregnancy while also highlighting knowledge gaps regarding understudied pathways. ABSTRACT: The progression from conception through to the postpartum period represents an extraordinary period of physiological adaptation in the mother to support the growth and development of the fetus. Healthy, normotensive human pregnancies are associated with striking increases in both plasma volume and sympathetic nerve activity, yet normal or reduced blood pressure; it represents a unique period of apparent healthy sympathetic hyperactivity. However, how this normal blood pressure is achieved in the face of sympathoexcitation, and the mechanisms responsible for this increased activity are unclear. Importantly, sympathetic activation has been implicated in hypertensive pregnancy disorders - the leading causes of maternal-fetal morbidity and mortality in the developed world. An understudied link between pregnancy and the development of maternal hypertension may lie in the sympathetic nervous system regulation of blood pressure. This brief review presents the latest data on sympathoexcitation in both healthy and hypertensive pregnancies, and concurrent adaptations along the neurovascular cascade.