Evaluating Pathophysiological Mechanisms of Acute and Chronic Heat Stress on Maternal and Fetal Health

Study Results

Results pending

The study team has not published outcome measurements, participant flow, or safety data for this trial yet. Check back later for updates.

Basic Information

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Recruitment Status

COMPLETED

Clinical Phase

NA

Total Enrollment

24 participants

Study Classification

INTERVENTIONAL

Study Start Date

2024-05-15

Study Completion Date

2024-08-15

Brief Summary

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This study examined the effects of environmental heat and physical work on maternal thermoregulation and fetal physiology in late pregnancy. Twenty-four healthy pregnant women at 28-32 weeks of gestation completed four randomized and counterbalanced 3-hour experimental scenarios combining two thermal conditions (temperate 20 °C and warm 30 °C, both at 45% relative humidity, shaded) and two physical workload intensities (light and moderate treadmill walking). Each scenario included 1 hour of passive seated exposure, 1 hour of treadmill walking, and 1 hour of seated recovery. Maternal thermoregulatory, cardiovascular, perceptual, and hydration responses were monitored continuously, while fetal heart rate and Doppler-derived indices of uterine, umbilical, and middle cerebral artery blood flow were assessed at baseline, end of passive exposure, end of work, and end of recovery. The aims of the study were: (1) to characterize maternal physiological and perceptual responses to heat exposure and physical work; (2) to determine whether maternal physiological heat strain directly affects fetal cardiovascular strain and maternal-fetal hemodynamics; and (3) to examine whether maternal characteristics, particularly body mass index and age, influence maternal thermoregulatory responses and fetal susceptibility to heat stress.

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Detailed Description

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Conditions

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Thermally Neutral Condition With Light-intensity Work Thermally Neutral Condition With Moderate-intensity Work Warm Condition With Light-intensity Work Warm Condition With Moderate-intensity Work

Study Design

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Allocation Method

RANDOMIZED

Intervention Model

CROSSOVER

Primary Study Purpose

BASIC_SCIENCE

Blinding Strategy

NONE

Study Groups

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Temperate-Light

Participants were exposed to a temperate environment (20 °C, 45% relative humidity, shaded) for a 3-hour protocol consisting of 1 hour passive seated exposure, 1 hour of light-intensity treadmill walking (alternating between 2 and 3 METs \[Metabolic Equivalents\] every 10 minutes), and 1 hour seated recovery.

Group Type OTHER

Heat and Physical Work Exposure Protocol

Intervention Type OTHER

A controlled 3-hour environmental chamber protocol consisting of 1 hour of passive seated exposure, 1 hour of treadmill walking at prescribed light or moderate intensities (alternating between 2-3 METs or 3-4 METs every 10 minutes), and 1 hour of seated recovery. Each session was conducted under either temperate (20 °C, 45% relative humidity, shaded) or warm (30 °C, 45% relative humidity, shaded) environmental conditions. Environmental settings, workload intensity, and timing were standardized across all participants.

Temperate-Moderate

Participants were exposed to a temperate environment (20 °C, 45% relative humidity, shaded) for a 3-hour protocol consisting of 1 hour passive seated exposure, 1 hour of moderate-intensity treadmill walking (alternating between 3 and 4 METs every 10 minutes), and 1 hour seated recovery.

Group Type OTHER

Heat and Physical Work Exposure Protocol

Intervention Type OTHER

A controlled 3-hour environmental chamber protocol consisting of 1 hour of passive seated exposure, 1 hour of treadmill walking at prescribed light or moderate intensities (alternating between 2-3 METs or 3-4 METs every 10 minutes), and 1 hour of seated recovery. Each session was conducted under either temperate (20 °C, 45% relative humidity, shaded) or warm (30 °C, 45% relative humidity, shaded) environmental conditions. Environmental settings, workload intensity, and timing were standardized across all participants.

Warm-Light

Participants were exposed to a warm environment (30 °C, 45% relative humidity, shaded) for a 3-hour protocol consisting of 1 hour passive seated exposure, 1 hour of light-intensity treadmill walking (alternating between 2 and 3 METs every 10 minutes), and 1 hour seated recovery.

Group Type OTHER

Heat and Physical Work Exposure Protocol

Intervention Type OTHER

A controlled 3-hour environmental chamber protocol consisting of 1 hour of passive seated exposure, 1 hour of treadmill walking at prescribed light or moderate intensities (alternating between 2-3 METs or 3-4 METs every 10 minutes), and 1 hour of seated recovery. Each session was conducted under either temperate (20 °C, 45% relative humidity, shaded) or warm (30 °C, 45% relative humidity, shaded) environmental conditions. Environmental settings, workload intensity, and timing were standardized across all participants.

Warm-Moderate

Participants were exposed to a warm environment (30 °C, 45% relative humidity, shaded) for a 3-hour protocol consisting of 1 hour passive seated exposure, 1 hour of moderate-intensity treadmill walking (alternating between 3 and 4 METs every 10 minutes), and 1 hour seated recovery.

Group Type OTHER

Heat and Physical Work Exposure Protocol

Intervention Type OTHER

A controlled 3-hour environmental chamber protocol consisting of 1 hour of passive seated exposure, 1 hour of treadmill walking at prescribed light or moderate intensities (alternating between 2-3 METs or 3-4 METs every 10 minutes), and 1 hour of seated recovery. Each session was conducted under either temperate (20 °C, 45% relative humidity, shaded) or warm (30 °C, 45% relative humidity, shaded) environmental conditions. Environmental settings, workload intensity, and timing were standardized across all participants.

Interventions

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Heat and Physical Work Exposure Protocol

A controlled 3-hour environmental chamber protocol consisting of 1 hour of passive seated exposure, 1 hour of treadmill walking at prescribed light or moderate intensities (alternating between 2-3 METs or 3-4 METs every 10 minutes), and 1 hour of seated recovery. Each session was conducted under either temperate (20 °C, 45% relative humidity, shaded) or warm (30 °C, 45% relative humidity, shaded) environmental conditions. Environmental settings, workload intensity, and timing were standardized across all participants.

Intervention Type OTHER

Eligibility Criteria

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Inclusion Criteria

* Healthy pregnant women between 28 and 32 weeks of gestation
* Singleton pregnancy
* Habitually heat-acclimatized, defined as daily exposure to outdoor environmental conditions equal to or warmer than those used in the study
* Able to perform treadmill walking at light and moderate intensities
* Willing and able to attend all laboratory sessions
* Provided written informed consent
* Age 18 years or older

Exclusion Criteria

* Multiple pregnancy (e.g., twins, triplets)
* Chronic medical conditions, including but not limited to:

* Hypertension
* Diabetes
* HIV
* Obstetric complications, including:

* Pre-eclampsia
* Severe anemia
* Acute infections, including urinary tract infection
* Any contraindication to exercise based on the Physical Activity Readiness for Pregnancy (PARmed-X for Pregnancy) checklist
* Inability to comply with the study procedures or scheduled visits
* Any condition deemed by investigators to compromise participant safety or data integrity

Minimum Eligible Age

18 Years

Eligible Sex

FEMALE

Accepts Healthy Volunteers

Yes