Leg Heating in Pregnant Women With Obesity

April 15, 2026 updated by: Qi Fu, University of Texas Southwestern Medical Center

Vascular and Neural Mechanisms of Chronic Leg Heating in Pregnant Women With Obesity

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.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Detailed Description

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.

Study Type

Interventional

Enrollment (Estimated)

118

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact Backup

Study Locations

  • United States
    • Texas
      • Dallas, Texas, United States, 75231
        • Recruiting
        • UT Southwestern Medical Center; Institute for Exercise and Environmental Medicine
        • Contact:

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria:

  • Women with overweight or obesity (self-reported pre-pregnancy body mass index ≥25 kg/m2) between 10-14 weeks of gestation and aged 18-45 years old will be enrolled.
  • Both normotensive and hypertensive (office sitting systolic BP 140-150 mmHg and/or diastolic BP 90-100 mmHg) pregnant women will be enrolled if they are not on any antihypertensive drug treatment.
  • We will enroll both nulliparous and multiparous women.
  • There is no restriction regarding race/ethnicity and socioeconomic status.
  • Women with a history of HDP will be allowed to participate.
  • Women taking low-dose aspirin will be allowed to participate and aspirin use will be documented.

Exclusion Criteria:

  • Current multiple pregnancies (e.g., twins, triplets, etc.).
  • Known major fetal chromosomal or anatomical abnormalities diagnosed during the study.
  • Recurrent miscarriage (three or more, to avoid antiphospholipid antibody syndrome).
  • Office sitting BP <100/55 mmHg or >150/100 mmHg (for safety reasons).
  • Evidence of cardiovascular, pulmonary, or neurological diseases.
  • Diabetes mellitus (to avoid its effects on vascular endothelial function and sympathetic vasoconstriction).
  • Kidney disease (serum creatinine >0.9 mg/dL).
  • Clinical known deep vein thrombosis, clinical symptoms and history of deep vein thrombosis, or dermatological lesions.
  • History of drug or alcohol abuse within the last 2 years.
  • Current tobacco use.
  • Pregnant women who do not have air conditioning at home during summer (for safety reasons).

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Other
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Single

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Sauna blanket set at 65°C
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
Participants will perform home-based leg heating using a portable sauna blanket set at different temperature.
Placebo Comparator: Sauna blanket set at 35°C
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.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Change in vascular endothelial function
Time Frame: Baseline, 16 weeks after leg heating
Change in vascular endothelial function assessed by brachial artery flow-mediated vasodilation using the Doppler ultrasound technique
Baseline, 16 weeks after leg heating
Change in sympathetic neural control
Time Frame: Baseline, 16 weeks after leg heating
Change in sympathetic neural control assessed by muscle sympathetic nerve (re)activity using the microneurographic technique
Baseline, 16 weeks after leg heating
Change in sympathetic vascular transduction
Time Frame: Baseline, 16 weeks after leg heating
Change in sympathetic vascular transduction assessed using the microneurographic and Doppler ultrasound techniques
Baseline, 16 weeks after leg heating

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Change in blood concentration of nitrate
Time Frame: Baseline, 16 weeks after leg heating
Blood concentration of nitrate will be used to estimate nitric oxide bioavailability
Baseline, 16 weeks after leg heating
Change in blood concentration of nitrite
Time Frame: Baseline, 16 weeks after leg heating
Blood concentration of nitrite will be used to estimate nitric oxide bioavailability
Baseline, 16 weeks after leg heating
Change in L-arginine level
Time Frame: Baseline, 16 weeks after leg heating
Baseline, 16 weeks after leg heating
Change in asymmetric dimethylarginine level
Time Frame: Baseline, 16 weeks after leg heating
Baseline, 16 weeks after leg heating
Change in 3-nitrotyrosine level
Time Frame: Baseline, 16 weeks after leg heating
Baseline, 16 weeks after leg heating
Change in concentration of endothelin-1
Time Frame: Baseline, 16 weeks after leg heating
Baseline, 16 weeks after leg heating
Change in 24-hour ambulatory blood pressure
Time Frame: Baseline, 16 weeks after leg heating
Baseline, 16 weeks after leg heating
Change in placental growth factor level
Time Frame: Baseline, 16 weeks after leg heating
Baseline, 16 weeks after leg heating
Change in solube fms-like tyrosine kinase-1 level
Time Frame: Baseline, 16 weeks after leg heating
Baseline, 16 weeks after leg heating
Change in soluble endoglin level
Time Frame: Baseline, 16 weeks after leg heating
Baseline, 16 weeks after leg heating

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

University of Texas Southwestern Medical Center

Investigators

  • Principal Investigator: Qi Fu, MD, PhD, UT Southwestern Medical Center; Institute for Exercise and Environmental Medicine

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

August 1, 2025

Primary Completion (Estimated)

January 31, 2030

Study Completion (Estimated)

April 30, 2030

Study Registration Dates

First Submitted

March 19, 2025

First Submitted That Met QC Criteria

April 9, 2025

First Posted (Actual)

April 17, 2025

Study Record Updates

Last Update Posted (Actual)

April 17, 2026

Last Update Submitted That Met QC Criteria

April 15, 2026

Last Verified

April 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • STU20250500

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

Only deidentified individual participant data will be available to other researchers.

IPD Sharing Time Frame

After the manuscripts are published.

IPD Sharing Supporting Information Type

  • STUDY_PROTOCOL
  • SAP
  • ICF
  • ANALYTIC_CODE
  • CSR

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

Clinical Trials on High-risk Pregnancy

Clinical Trials on Leg heating

Search Similar Trials

Sponsors and Collaborators

Medical Conditions

Drug Interventions

CROs by country

CROs in New Zealand

Conditions

Rare Diseases

Drug Interventions

Dietary Supplements

Sponsor/Collaborators

Locations

Subscribe