NCT07687745 · University of Arizona
Breathing for Two: Inspiratory Muscle Strength Training for Supporting Healthy Blood Pressure in Pregnancy
What this study is about
This is an interventional study that will test whether a breathing exercise called Inspiratory Muscle Strength Training (IMST) can safely and effectively lower blood pressure during late pregnancy. The goal is to see if a home-based breathing training can help prevent or reduce high blood pressure disorders in pregnancy.
View original scientific description
This is an interventional study that will test whether a breathing exercise called Inspiratory Muscle Strength Training (IMST) can safely and effectively lower blood pressure during late pregnancy. The goal is to see if a home-based breathing training can help prevent or reduce high blood pressure disorders in pregnancy. The main objectives are to make sure the training is safe and tolerable for pregnant women and to examine blood pressure and blood vessel health. Participants in their third trimester will be randomly assigned to either do moderate resistance IMST or a minimal resistance sham IMST, for 5 to 8 minutes a day over six weeks.
Interventions
OTHER
Exercise at 15% PI max
Minimal resistance training, similar to yoga, for 5 to 8 minutes a day over six weeks.
OTHER
Exercise at 50% PI max
Moderate resistance training, similar to strength training for 5 to 8 minutes a day over six weeks.
Primary outcome measures
Incidence of Maternal and Fetal Safety Events During Inspiratory Muscle Strength Training (IMST)
Time frame: 6 weeks
Percentage of training sessions associated with abnormal post-training fetal heart rate (FHR) tracing, or with maternal oxygen desaturation (SpO2) or symptoms (e.g., perceived exertion, lightheadedness, hyperventilation), as assessed by study staff during non-stress test (NST) and clinic visits.
Adherence to IMST Training and Home Blood Pressure (BP) Monitoring
Time frame: 6 weeks
Percentage of prescribed daily IMST training sessions and daily home BP measurements completed by each participant, as captured via training device data and MyCap entries.
Change from Baseline in Systolic Blood Pressure
Time frame: 6 weeks
Change in systolic BP (mmHg), measured via validated automated oscillometric sphygmomanometer (Omron BP7450) per ESH-IP protocol, comparing IMST and sham IMST groups.
Change from Baseline in Endothelial Function as Assessed by Post-Occlusive Reactive Hyperemia (PORH)
Time frame: 6 weeks
Change in cutaneous microvascular blood flow response (perfusion units) following brief arterial occlusion, measured via Laser Doppler Blood FlowMetry, comparing IMST and sham IMST groups.
Change from Baseline in Urinary Nitrite/Nitrate Concentration
Time frame: Change in urinary nitrite/nitrate concentration (µM), measured weekly via Griess colorimetric assay (Cayman Nitrite Colorimetric Assay), as an indirect marker of nitric oxide bioavailability.
6 weeks
Who can participate
This study lists these criteria on ClinicalTrials.gov. A study coordinator reviews eligibility during screening — this page does not determine whether you qualify.
Inclusion criteria
- Pregnant (32 to 34 weeks of gestation, confirmed by ultrasound, at the time of first training session, eligible patients may consent/enrolled earlier in pregnancy)
- Singleton pregnancy
- Age 18 to 55
- Able to read English and provide consent
- Possess smartphone for syncing the AiroFit and Omron devices using Bluetooth and completing online surveys
- Smartphone updated to iOS 12+ or Android 11+
- No contraindication for moderate exercise at time of enrollment
- Not planning delivery for at least one month at time of enrollment (\< 38 weeks of gestation)
- Willing to adhere to AiroFit device use throughout study period
- Must already be scheduled, or in the process of scheduling, for weekly NST appointments by 32 to 34 weeks gestational age (per provider order / due to obstetric indication) Lower-Risk Pregnancy Cohort Inclusion Criteria:
- No history or evidence of hypertensive disorders of pregnancy
- May be undergoing antenatal testing for:
- Conception via in vitro fertilization, BMI ≥ 35, an advanced maternal age (age \>/=35), or other condition not listed in
Exclusion criteria
- or 'higher risk for HDP group' but is recommended for antenatal testing. Higher-Risk Pregnancy Cohort Inclusion Criteria:
- Conditions associated with higher risk of developing HDP, including:
- Gestational diabetes mellitus, chronic hypertension, gestational hypertension, or a history of preeclampsia in a previous pregnancy Exclusion Criteria:
- Younger than 18 or older than 55 years of age
- Multiple gestation (twin or higher-order pregnancy)
- Fetal chromosomal abnormalities or major anatomical anomalies
- Planning to deliver earlier than 38 weeks or within 4 weeks of study enrollment
- Any contraindication for moderate exercise (e.g., cardiomyopathy, congenital cardiac conditions)
- Deep vein thrombosis
- Complications in current pregnancy including intrauterine growth restriction (IUGR), oligohydramnios, preeclampsia, or severe-range blood pressures (\>/=160/110 or \<100/60)
- Active vaginal bleeding, or history of coagulopathy
- Placenta previa or other placental abnormalities (including placental cyst or abruption)
- Signs of labor
- Current substance use disorder
- History of neurological, respiratory, head/neck, or thoracic surgeries, or conditions such as collapsed lung or perforated eardrum
- Individuals with any of the following:
- Chronic obstructive pulmonary disorder (COPD)
- Severe asthma
- Severe ischemic heart disease
- Left-sided heart failure
- Chronic laryngitis, chronic bronchitis, emphysema, pneumonia
- Latent or active tuberculosis
- Chronic cough
- Neurological problems (e.g. seizure disorder)
- Severe scoliosis with no history of surgical correction or management.
- Organ transplant
- HIV or other immunocompromising conditions
- Autoimmune disease with possible vascular complications (e.g. Lupus)
- Significant respiratory compromise (e.g., severe dyspnea, O₂ saturation \<95%, uncontrolled asthma, history of pneumothorax)
Where
- Tucson, Arizona
Collaborators
Banner University Medical Center
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Frequently asked questions
What is a clinical trial?
A clinical trial is a research study that tests new medical treatments, drugs, devices, or procedures to determine their safety and effectiveness. Trials are carefully designed and monitored to protect participants while advancing medical knowledge.
Is it safe to participate?
Clinical trials follow strict safety guidelines and ethical standards. Trials must be reviewed and approved, and participants are closely monitored by medical professionals throughout the study. You can withdraw at any time if you choose.
Will I be compensated?
Many clinical trials offer compensation for your time, travel expenses, and inconvenience. The specific compensation varies by study and will be discussed during the screening process. All study-related medical care is typically provided at no cost to participants.
Will I receive a placebo instead of treatment?
When effective treatment exists, participants typically receive either the standard treatment plus the study intervention, or the standard treatment plus placebo. You would not be denied effective care. Placebos are primarily used when no proven treatment is available, or in addition to standard care. Your trial consent form will clearly explain what treatments you may receive.
Can I leave a trial if I change my mind?
Absolutely. Participation in clinical trials is completely voluntary. You have the right to withdraw from the study at any time, for any reason, without penalty or loss of benefits to which you are otherwise entitled.
How long does a clinical trial last?
Trial duration varies widely depending on the study design and purpose. Some trials last just a few weeks, while others may continue for months or years. The study coordinator will provide specific timeline information during your screening call.
Data: ClinicalTrials.gov · synced Jul 7, 2026 · Source of record for eligibility and locations