An interventional study of Leg heating in High-risk Pregnancy, sponsored by University of Texas Southwestern Medical Center. Recruiting at 1 site in United States. Open to female participants aged 18 Years to 45 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-04-17.
Sponsored by University of Texas Southwestern Medical Center · Not applicable, Interventional, and Other
Obesity is a major risk factor for hypertensive disorders of pregnancy (HDP). The underlying mechanisms are largely unclear, but maternal vascular endothelial dysfunction is likely involved. Endothelial dysfunction in HDP could be attributed to 1) alterations in the L-arginine/nitric oxide (NO) pathway, and 2) an increase in endothelin-1 (ET-1). Additionally, augmented sympathetic vasoconstriction may also contribute to HDP. Chronic (repeated) whole-body heat exposure has been shown to increase NO bioavailability, decrease ET-1, and cause functional and structural adaptations in the vasculature. All these can improve vascular function, attenuate sympathetic (re)activity, lower blood pressure (BP), and reduce cardiovascular risk in non-pregnant individuals. Whether this is also true after regional (leg) heating in high-risk pregnant women is unknown. The investigators' central hypothesis is that chronic leg heating will be effective in improving vascular endothelial function and attenuating sympathetic vasoconstriction, leading to a reduction of the risk for HDP in pregnant women with obesity. The overarching goal of this proposal is to determine the vascular and neural effects of chronic leg heating in obese pregnancy. The study team plans to enroll pregnant women with obesity between 12-14 weeks of gestation and randomly assign them to either an intervention group or a control group (1:1 ratio). Participants in the intervention group will perform 16 weeks of home-based leg heating using a portable sauna blanket up to the hip (temperature of the blanket will be set at 65°C, 4 times/week, 45 min/session), whereas women in the control group will set the temperature of the blanket at 35°C at the same frequency and duration. Participants will be evaluated at baseline and then at 28-30 weeks of gestation. Aim 1 will determine the effects of chronic leg heating on maternal vascular function and surrogate markers of HDP. Aim 2 will determine the effects of chronic leg heating on sympathetic vasoconstriction and BP. Findings from this project will provide insight on the extent and potential mechanisms of how chronic leg heating works for improving vascular endothelial function and sympathetic vasoconstriction in pregnant women with obesity. Results obtained will set a foundation for future large multicenter clinical trials to determine the efficacy and generalizability of home-based leg heat therapy as a safe, ease-of-use, cost-effective, and non-drug approach for reducing the risk of HDP.
Obesity is a major risk factor for hypertensive disorders of pregnancy (HDP). The underlying mechanisms are unclear, but maternal vascular endothelial dysfunction is likely involved. Endothelial dysfunction in HDP could be attributed in part to: 1) alterations in the L-arginine/nitric oxide (NO) pathway, and 2) an increase in endothelin-1 (ET-1). Conversely, augmented sympathetic vasoconstriction may also contribute to the development of HDP in women with obesity. Exercise training increases NO production, decreases ET-1, improves vascular function, attenuates sympathetic (re)activity, and reduces the risk for HDP. However, pregnant women, especially those with obesity, have poor adherence to exercise. Thus, there is an urgent need to develop novel, safe, convenient, low-cost, and well-tolerated strategies that have similar beneficial effects as exercise training. One such novel approach may be "heating".
During passive whole-body heating, body core temperature increases and cutaneous and muscle vascular resistance decreases, leading to increases in blood flow and shear stress throughout the entire arterial tree. Chronic (i.e., repeated) exposure to these temperature-dependent responses induces an increase in NO bioavailability, a decrease in ET-1, and functional and structural adaptations in the vasculature - all these can improve vascular function, attenuate sympathetic (re)activity, lower blood pressure (BP), and reduce the risk for cardiovascular morbidity and mortality. Evidence suggests that maternal body core temperature below 38.9°C is safe for the fetus.
The study team proposes to use regional (e.g., leg) rather than whole-body (e.g., hot tub or sauna) heating, since leg heating does not substantially elevate body core temperature (i.e., 37.32°C at peak in pregnant women with obesity in our pilot study), is more tolerable than whole-body heating, and can be performed in-home. Importantly, the study team's preliminary work showed that chronic home-based leg heating is safe, and can improve endothelial function, attenuate sympathetic vasoconstriction, and reduce ambulatory awake BP in pregnant women with obesity.
The investigators' central hypothesis is that chronic leg heating will be effective in improving vascular endothelial function and attenuating sympathetic vasoconstriction, leading to a reduction of the risk for HDP in pregnant women with obesity.
Aim 1: Determine the effects of chronic leg heating on maternal vascular function and surrogate markers of HDP.
Hypothesis 1: Chronic leg heating will improve vascular endothelial function due to an increase in NO bioavailability and a decrease in ET-1, which may be associated with a reduction of the risk for HDP in pregnant women with obesity.
Aim 2: Determine the effects of chronic leg heating on sympathetic vasoconstriction and BP.
Hypothesis 2: Chronic leg heating will attenuate sympathetic-dependent vasoconstriction due to a decrease in sympathetic (re)activity, which may be associated with a reduction of BP in pregnant women with obesity.
Impact: Findings from this project will provide insight on the extent and potential mechanisms of how chronic leg heating works for improving vascular endothelial function and sympathetic vasoconstriction in pregnant women with obesity. Results obtained will set a foundation for future large multicenter clinical trials to determine the efficacy and generalizability of home-based leg heat therapy as a safe, ease-of-use, cost-effective, and non-drug approach for reducing the risk of HDP, and its most severe form, preeclampsia.
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Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
BMI (body mass index)
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
The temperature of the sauna blanket will be set at 65°C and participants will perform home-based leg heating 4 times per week, 45 minutes per session.
Other: Leg heating
The temperature of the sauna blanket will be set at 35°C and participants will perform home-based leg heating 4 times per week, 45 minutes per session.
Other: Leg heating
Participants will perform home-based leg heating using a portable sauna blanket set at different temperature.
Change in vascular endothelial function
Change in vascular endothelial function assessed by brachial artery flow-mediated vasodilation using the Doppler ultrasound technique
Time frame: Baseline, 16 weeks after leg heating
Change in sympathetic neural control
Change in sympathetic neural control assessed by muscle sympathetic nerve (re)activity using the microneurographic technique
Time frame: Baseline, 16 weeks after leg heating
Change in sympathetic vascular transduction
Change in sympathetic vascular transduction assessed using the microneurographic and Doppler ultrasound techniques
Time frame: Baseline, 16 weeks after leg heating
Change in blood concentration of nitrate
Blood concentration of nitrate will be used to estimate nitric oxide bioavailability
Time frame: Baseline, 16 weeks after leg heating
Change in blood concentration of nitrite
Blood concentration of nitrite will be used to estimate nitric oxide bioavailability
Time frame: Baseline, 16 weeks after leg heating
Change in L-arginine level
Time frame: Baseline, 16 weeks after leg heating
Change in asymmetric dimethylarginine level
Time frame: Baseline, 16 weeks after leg heating
Change in 3-nitrotyrosine level
Time frame: Baseline, 16 weeks after leg heating
Change in concentration of endothelin-1
Time frame: Baseline, 16 weeks after leg heating
Change in 24-hour ambulatory blood pressure
Time frame: Baseline, 16 weeks after leg heating
Change in placental growth factor level
Time frame: Baseline, 16 weeks after leg heating
Change in solube fms-like tyrosine kinase-1 level
Time frame: Baseline, 16 weeks after leg heating
Change in soluble endoglin level
Time frame: Baseline, 16 weeks after leg heating
Plan to share: Yes — Only deidentified individual participant data will be available to other researchers.
Supporting information: Study protocol, Statistical analysis plan, Informed consent form, Clinical study report, Analytic code
Time frame: After the manuscripts are published.
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