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

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

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.

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