Aquatic Exercise and Thermoregulation in Pregnancy

Influence of prenatal aquatic activities on fetal outcomes and maternal physical and mental outcomes: a systematic review and meta-analysis

BACKGROUND

Aquatic activities are becoming increasingly popular as a form of exercise during pregnancy. However, the effects of these activities on the physical and mental health outcomes of pregnant women during and after pregnancy as well as fetal outcomes remain unclear. This meta-analysis evaluated the current evidence regarding the effects of aquatic activities during pregnancy on neonatal and maternal outcomes.

METHODS

Three databases (PubMed, Cochrane Central electronic database, Embase) were searched from inception to July 17, 2024 for randomized controlled trials (RCTs) comparing the effects of aquatic activities versus standard prenatal care or no exercise on neonatal and maternal outcomes. Pooled outcome measures were determined using random-effects models.

RESULTS

Ten RCTs including 1949 patients met the criteria for inclusion in this meta-analysis. The results showed that prenatal aquatic activities could significantly improve maternal weight control (mean difference [MD]= -0.91, 95% confidence interval [CI]= -1.64 to -0.18, P = 0.01, I2 = 0.00%), improve maternal quality of life (standard mean difference [SMD] = 0.16, 95%CI = 0.03 to 0.28, P = 0.01, I2 = 0.00%), and extend fetal birth length (MD = 0.48, 95%CI = 0.10 to 0.87, P = 0.01, I2 = 0.00%) compared with standard prenatal care or no exercise, while no significant differences were observed in fetal birth weight, Apgar score at 1 min, Apgar score at 5 min, pH of umbilical cord blood, gestational age, rate of preterm delivery, incidence of postnatal depression and mode of delivery.

CONCLUSIONS

Prenatal aquatic activities can significantly improve maternal weight control and quality of life during pregnancy, and may promote longer birth length. However, additional studies are needed to confirm these findings.

Cool mama: Temperature regulation during high-intensity interval running in pregnant elite and recreational athletes

Background

Regular exercise during pregnancy is beneficial, but athletes often exceed the recommended 150 min of moderate-intensity activity, incorporate high-intensity exercises. The upper limit for exercise intensity and duration on fetal and maternal safety remains uncertain. A concern is a maternal core body temperature of >39.0 °C, potentially increase the risk of heat-related fetal malformations and complications during pregnancy. Blood flow redirection for thermoregulation could compromise fetal cardiovascular function, increasing the risk of miscarriage and preterm labor. This study evaluated whether pregnant women (gestational weeks 25-35) were at risk of exceeding a core body temperature of 39.0 °C during high-intensity running. We also investigated effects on skin temperature, fluid loss, and thermal sensation, comparing pregnant athletes to non-pregnant controls.

Methods

In this comparative cross-sectional study, 30 elite and recreational athletes (pregnant n = 15) completed up to five high-intensity treadmill-intervals. Core and skin temperature were continuously measured. Body weight was utilized to calculate the amount of fluid loss.

Results

Highest core body temperature were 38.76 °C and 39.56 °C in one pregnant and non-pregnant participant, respectively. Pregnant participants had lower core body temperatures (mean difference -0.47 °C, p ≤ 0.001) initially and a smaller increase (0.10 °C, p ≤ 0.003) during later intervals compared with the non-pregnant controls. Pregnant participants also showed a greater increase in skin temperature (4.08 ± 0.72 °C vs. 3.25 ± 0.86 °C, p = 0.008) and fluid loss (0.81 ± 0.19 L vs. 0.50 ± 0.12 L, p˂0.001).

Conclusion

Physiological changes in pregnancy may enhance thermoregulation, indicating that high-intensity interval runs are unlikely to pose a risk of exceeding a core body temperature of 39 °C for pregnant athletes.

Effect of different physical activity interventions on perinatal depression: a systematic review and network meta-analysis

BACKGROUND

Perinatal depression can have profound impacts on both families and society. Exercise therapy is gradually becoming a widely used adjunct treatment for perinatal depression. Some studies have already focused on the relationship between physical activity and perinatal depression (PND). However, there is currently a lack of systematic and comprehensive evidence to address the crucial question of making optimal choices among different forms of physical activity. This study aims to compare and rank different physical activity intervention strategies and identify the most effective one for perinatal depression.

METHODS

Four databases, namely PubMed, Cochrane Library, Embase, and Web of Science, were searched for randomized controlled trials assessing the impact of physical activity interventions on perinatal depression. The search covered the period from the inception of the databases until May 2024. Two researchers independently conducted literature screening, data extraction, and quality assessment. Network meta-analysis was performed using Stata 15.1.

RESULTS

A total of 48 studies were included in the analysis. The results indicate that relaxation therapy has the most effective outcome in reducing perinatal depression (SUCRA = 99.4%). Following that is mind-body exercise (SUCRA = 80.6%). Traditional aerobics and aquatic sports were also effective interventions (SUCRA = 70.9% and 67.1%, respectively).

CONCLUSION

Our study suggests that integrated mental and physical (MAP) training such as relaxation therapy and mind-body exercise show better performance in reducing perinatal depression. Additionally, while exercise has proven to be effective, the challenge lies in finding ways to encourage people to maintain a consistent exercise routine.

TRIAL REGISTRATION

This study has been registered on PROSPERO (CRD 42,023,469,537).

A systematic review on the physical, mental, and occupational effects of exercise on pregnant women

Complications in pregnancy have been proven to be less frequent with exercise. The American College of Obstetrics and Gynecology suggests pregnant women should exercise an average of 20 to 30 min a day; however, only 13% of pregnant women exercise throughout their pregnancy. This amount could be improved if women are aware that exercise: 1. Can help avoid pregnancy complications or death and 2. Comes in various forms with different health outcomes associated with it. For this reason, this systematic literature review was conducted to review different types of exercise for pregnant women. Peer-reviewed articles were selected to discuss the benefits of the most researched exercises for pregnant women, which included yoga, resistance training, aquatic exercises, dance, and aerobic exercise such as running, walking, and cycling. Data from the review revealed that different types of exercises led to various benefits at different stages of pregnancy. Aquatic activities and yoga helped pregnant women toward the end of their pregnancies, whereas resistance training, dance, and aerobic exercises provided the most benefits during the first trimester. Other studies found that any form of exercise for 30 min a day or every other day for 60 min provided extensive beneficial results. Ultimately, this information could be used to create individualized exercise plans for pregnant women to adhere to throughout their pregnancy.

Heat production during exercise in pregnancy: discerning the contribution of total body weight

Studies have reported enhanced thermoregulatory function as pregnancy progresses; however, it is unclear if differences in thermoregulation are attributed to weight gain or other physiological changes. This study aimed to determine if total body weight will influence thermoregulation (heat production (Hprod)), heart rate, and perceptual measurements in response to weight-bearing exercise during early to late pregnancy. A cross-sectional design of healthy pregnant women at different pregnancy time points (early, T1; middle, T2; late, T3) performed a 7-stage weight-bearing incremental exercise protocol. Measurements of Hprod, HR, and RPE were examined. Two experimental groups were studied: (1) weight matched and (2) non-weight matched, in T1, T2, and T3. During exercise, equivalent Hprod at T1 (326 ± 88 kJ), T2 (330 ± 43 kJ), and T3 (352 ± 52 kJ) (p = 0.504); HR (p = 0.830); and RPE (p = 0.195) were observed in the WM group at each time point. In the NWM group, Hprod (from stages 1-6 of the exercise) increased across pregnancy time points, T1 (291 ± 76 kJ) to T2 (347 ± 41 kJ) and T3 (385 ± 47 kJ) (p < 0.001). HR increased from T1 to T3 in the warm-up to stage 6 (p = 0.009). RPE did not change as pregnancy time point progressed (p = 0.309). Total body weight, irrespective of pregnancy time point, modulates Hprod and HR during exercise. Therefore, accounting for total body weight is crucial when comparing thermoregulatory function during exercise across pregnancy.

A century of exercise physiology: concepts that ignited the study of human thermoregulation. Part 3: Heat and cold tolerance during exercise

In this third installment of our four-part historical series, we evaluate contributions that shaped our understanding of heat and cold stress during occupational and athletic pursuits. Our first topic concerns how we tolerate, and sometimes fail to tolerate, exercise-heat stress. By 1900, physical activity with clothing- and climate-induced evaporative impediments led to an extraordinarily high incidence of heat stroke within the military. Fortunately, deep-body temperatures > 40 °C were not always fatal. Thirty years later, water immersion and patient treatments mimicking sweat evaporation were found to be effective, with the adage of cool first, transport later being adopted. We gradually acquired an understanding of thermoeffector function during heat storage, and learned about challenges to other regulatory mechanisms. In our second topic, we explore cold tolerance and intolerance. By the 1930s, hypothermia was known to reduce cutaneous circulation, particularly at the extremities, conserving body heat. Cold-induced vasodilatation hindered heat conservation, but it was protective. Increased metabolic heat production followed, driven by shivering and non-shivering thermogenesis, even during exercise and work. Physical endurance and shivering could both be compromised by hypoglycaemia. Later, treatments for hypothermia and cold injuries were refined, and the thermal after-drop was explained. In our final topic, we critique the numerous indices developed in attempts to numerically rate hot and cold stresses. The criteria for an effective thermal stress index were established by the 1930s. However, few indices satisfied those requirements, either then or now, and the surviving indices, including the unvalidated Wet-Bulb Globe-Thermometer index, do not fully predict thermal strain.

Effect of aerobic water exercise during pregnancy on epidural use and pain: A multi-centre, randomised, controlled trial

OBJECTIVE

The physical and psychological benefits of exercise during pregnancy are well established. However, the impact of exercise on pain during labour and the use of epidural analgesia has been less explored. The main aim of this study was to analyse the effectiveness and safety of moderate aerobic water exercise by pregnant women on the subsequent use of epidural analgesia during labour, induction of labour, mode of delivery, and pain perception.

DESIGN

A multi-centre, parallel, randomised, evaluator blinded, controlled trial in a primary care setting.

SETTING

Primary care centres in a health district of a tertiary obstetric metropolitan hospital in Mallorca, Spain.

PARTICIPANTS

Pregnant women (14 to 20 weeks' gestation) who had low risk of complications.

METHODS

Three hundred and twenty pregnant women were randomly assigned to two groups: women who practiced moderate aquatic aerobic exercise with usual antenatal care, and those who received usual prenatal care alone. The gynaecologist, anaesthesiologist and midwife who assisted the women during labour were blinded to group allocations. Principal outcome: use of epidural analgesia during labour. Other outcomes: use of epidural analgesia before 6 cm cervical dilation, labour pain, type of delivery, time of active labour, episiotomy or perineal tear, and induction of labour.

RESULTS

The exercise program did not affect the use of epidural analgesia (OR = 0.79, 95% CI = 0.44 to 1.40), vaginal delivery (OR = 1.35, 95% CI = 0.73 to 2.41), or caesarean section (OR = 0.94, 95% CI = 0.47 to 1.89). However, women in the exercise group reported less pain during labour (mean difference: -0.6, 95% CI = -1.11 to -0.09). The two groups (moderate aquatic aerobic exercise versus usual antenatal care) showed no significant differences in maternal or newborn adverse events.

CONCLUSION

Aquatic aerobic exercise during pregnancy had no effect on the use of epidural analgesia during labour, whereas pain perception was lower after aquatic exercise compared to usual care in pregnancy. The intervention was safe for pregnant women and their newborns.

Heat loss responses at rest and during exercise in pregnancy: A scoping review

BACKGROUND

The teratogenic risk associated with maternal hyperthermia (i.e., core temperature ≥39.0 °C) has been a crucial motive in understanding thermoregulatory responses in pregnancy. To date, a substantial number of studies have focused on core temperature responses in a wide range of exercise intensities, duration, and ambient temperatures. Fortunately, none have reported core temperatures exceeding 39.0 °C. Nonetheless, there are limited studies that have provided substantial insight into both dry and evaporative heat loss mechanisms involved in facilitating the maintenance of core temperature (≥39.0 °C) during heat stress in pregnant women. The purpose of this scoping review was to summarize the available literature that has assessed heat loss responses in studies of human pregnancy.

METHODS

A search strategy was developed combining the terms pregnancy, thermoregulation, and adaptation. A systematic search was performed in the following databases: PubMed, Embase, Scopus, and ProQuest. Studies eligible for inclusion included pregnant women between the ages of 18-40 years old, and at least one measurement of the following: sweating, blood flow, skin temperature, and behavioural responses. Retrieved data were categorized as evaporative (sweating), dry or behavioural heat loss responses and summarized narratively.

RESULTS

Thirty-three studies were included in this review (twenty-nine measured physiological responses and four measured behavioural responses). Studies suggest that during exercise, evaporative (sweating) and dry (skin blood flow and temperature) heat loss responses increase from early to late pregnancy in addition to greater cardiac output, blood volume and reduced vascular resistance. Behavioural practices related to heat loss responses are also influenced by cultural/religious expectations, personal preferences and sociodemographics.

CONCLUSION

The findings from this review suggest that pregnancy modifies evaporative (sweating), dry and behavioural heat loss. However, future studies have an opportunity to compare heat loss measurements accounting for gestational weight gain and thermal sensation/comfort scale to associate physiological responses with perceptual responses across pregnancy.

Effectiveness of Moderate-Intensity Aerobic Water Exercise during Pregnancy on Quality of Life and Postpartum Depression: A Multi-Center, Randomized Controlled Trial

Background: The global prevalence of postpartum depression is about 20%. This disease has serious consequences for women, their infants, and their families. The aim of this randomized clinical trial was to analyze the effectiveness and safety of a moderate-intensity aerobic water exercise program on postpartum depression, sleep problems, and quality of life in women at one month after delivery. Methods: This was a multi-center, parallel, randomized, evaluator blinded, controlled trial in a primary care setting. Pregnant women (14–20 weeks gestational age) who had low risk of complications and were from five primary care centers in the area covered by the obstetrics unit of Son Llatzer Hospital (Mallorca, Spain) were invited to participate. A total of 320 pregnant women were randomly assigned to two groups, an intervention group (moderate aquatic aerobic exercise) and a control group (usual prenatal care). One month after birth, sleep quality (MOS sleep), quality of life (EQ-5D), and presence of anxiety or depression (EPDS) were recorded. Findings: Women in the intervention group were less likely to report anxiety or depression on the EQ5D (11.5% vs. 22.7%; p < 0.05) and had a lower mean EPDS score (6.1 ± 1.9 vs. 6.8 ± 2.4, p < 0.010). The two groups had no significant differences in other outcomes, maternal adverse events, and indicators of the newborn status. Conclusion: Moderate-intensity aquatic exercise during pregnancy decreased postpartum anxiety and depressive symptoms in mothers and was safe for mothers and their newborns.

Acute Blood Pressure Effects in Older Adults with Hypertension After Different Modalities of Exercise: An Experimental Study

This study investigated the acute blood pressure (BP) effects of different exercise modalities in older adults with hypertension. Sixty volunteers were randomly assigned (n = 15/group) into different exercise protocols: resistance, bike, water-based exercise (WE), and a control session-all for ∼45 min. Clinic BP measurements were taken before, immediately after, and 15 and 30 min after protocols. The data were analyzed by one-way analysis of variance; generalized estimating equations, following Bonferroni post hoc (p < .05). Immediately after exercise, the systolic BP (SBP) increased in all exercise protocols (resistance exercise = Δ10.3, bike exercise = Δ5.8, WE = Δ9.5 mmHg; p < .001), while the diastolic BP was not altered. Afterward, the SBP reached the value observed before exercise. In Minute 30, only WE presented a significant reduction for SBP (WE = Δ-4.6 mmHg; p < .05). This study has important clinical implications in hemodynamic safety for acute BP increases immediately after exercises, as well as, in the SBP, reduction benefits for older adults with hypertension.

Water-based exercises in pregnancy: Apparent weight in immersion and ground reaction force at third trimester

BACKGROUND

The morphological alterations during pregnancy may affect the biomechanical loads during exercise practice. Aquatic exercises may suit pregnant women, who are recommended to exercise with low vertical ground reaction force loads. Therefore, the study aimed to determine the apparent weight reduction during immersion and the vertical ground reaction force of three specific water-based exercises in pregnant women at the third trimester.

METHODS

Eleven pregnant women volunteered to take part in the study [32.0 (SD 1.3) weeks, 28.1 (SD 5.7) years, 72.5 (SD 10.1) kg]. The protocol started with the participants immersed to the xiphoid process depth for the apparent weight assessment. Then, three water-based exercises (stationary running, frontal kick and butt kick) were randomly performed at a pre-selected cadence, with 5-min interval. The vertical ground reaction force was measured in each exercise and peak, impulse, contact time and swing time were determined. Repeated measures ANOVA was used (α = 0.05).

FINDINGS

The apparent weight reduction resulted a mean of 82.9 (SD 6.5)% of body weight. Peak, impulse, contact time and swing time revealed no significant difference between exercises (P > 0.05). Values of peak of vertical ground reaction force ranged from 0.67 to 0.72 units of body weight.

INTERPRETATION

Pregnant women at the third trimester can benefit from the apparent weight reduction during immersion for exercising. The three water-based exercises presented similar vertical ground reaction force values, which are considered as low odds for musculoskeletal injuries. Therefore, these findings highlight the safety of the water-based exercise program during pregnancy.

Effects of prenatal exercise on incidence of congenital anomalies and hyperthermia: a systematic review and meta-analysis

OBJECTIVE

To investigate the relationships between exercise and incidence of congenital anomalies and hyperthermia.

DESIGN

Systematic review with random-effects meta-analysis .

DATA SOURCES

Online databases were searched from inception up to 6 January 2017.

STUDY ELIGIBILITY CRITERIA

Studies of all designs were eligible (except case studies and reviews) if they were published in English, Spanish or French, and contained information on 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 [e.g., dietary; "exercise + co-intervention"]), comparator (no exercise or different frequency, intensity, duration, volume or type of exercise) and outcome (maternal temperature and fetal anomalies).

RESULTS

This systematic review and meta-analysis included 'very low' quality evidence from 14 studies (n=78 735) reporting on prenatal exercise and the odds of congenital anomalies, and 'very low' to 'low' quality evidence from 15 studies (n=447) reporting on maternal temperature response to prenatal exercise. Prenatal exercise did not increase the odds of congenital anomalies (OR 1.23, 95% CI 0.77 to 1.95, I²=0%). A small but significant increase in maternal temperature was observed from pre-exercise to both during and immediately after exercise (during: 0.26°C, 95% CI 0.12 to 0.40, I²=70%; following: 0.24°C, 95% CI 0.17 to 0.31, I²=47%).

SUMMARY/CONCLUSIONS

These data suggest that moderate-to-vigorous prenatal exercise does not induce hyperthermia or increase the odds of congenital anomalies. However, exercise responses were investigated in most studies after 12 weeks' gestation when the risk of de novo congenital anomalies is negligible.

Heat stress and fetal risk. Environmental limits for exercise and passive heat stress during pregnancy: a systematic review with best evidence synthesis

OBJECTIVE

Pregnant women are advised to avoid heat stress (eg, excessive exercise and/or heat exposure) due to the risk of teratogenicity associated with maternal hyperthermia; defined as a core temperature (T_core) ≥39.0°C. However, guidelines are ambiguous in terms of critical combinations of climate and activity to avoid and may therefore unnecessarily discourage physical activity during pregnancy. Thus, the primary aim was to assess T_core elevations with different characteristics defining exercise and passive heat stress (intensity, mode, ambient conditions, duration) during pregnancy relative to the critical maternal T_core of ≥39.0°C.

DESIGN

Systematic review with best evidence synthesis.

DATA SOURCES

EMBASE, MEDLINE, SCOPUS, CINAHL and Web of Science were searched from inception to 12 July 2017.

STUDY ELIGIBILITY CRITERIA

Studies reporting the T_core response of pregnant women, at any period of gestation, to exercise or passive heat stress, were included.

RESULTS

12 studies satisfied our inclusion criteria (n=347). No woman exceeded a T_core of 39.0°C. The highest T_core was 38.9°C, reported during land-based exercise. The highest mean end-trial T_core was 38.3°C (95% CI 37.7°C to 38.9°C) for land-based exercise, 37.5°C (95% CI 37.3°C to 37.7°C) for water immersion exercise, 36.9°C (95% CI 36.8°C to 37.0°C) for hot water bathing and 37.6°C (95% CI 37.5°C to 37.7°C) for sauna exposure.

CONCLUSION

The highest individual core temperature reported was 38.9°C. Immediately after exercise (either land based or water immersion), the highest mean core temperature was 38.3°C; 0.7°C below the proposed teratogenic threshold. Pregnant women can safely engage in: (1) exercise for up to 35 min at 80%-90% of their maximum heart rate in 25°C and 45% relative humidity (RH); (2) water immersion (≤33.4°C) exercise for up to 45 min; and (3) sitting in hot baths (40°C) or hot/dry saunas (70°C; 15% RH) for up to 20 min, irrespective of pregnancy stage, without reaching a core temperature exceeding the teratogenic threshold.