Trial Review

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Trial registered on ANZCTR


Registration number
ACTRN12625000702415
Ethics application status
Approved
Date submitted
2/06/2025
Date registered
2/07/2025
Date last updated
2/07/2025
Date data sharing statement initially provided
2/07/2025
Type of registration
Prospectively registered

Titles & IDs
Public title
A Study Protocol for a Randomised Control Trial to assess the Critical Environmental Limits for Pregnant Women during Light Exercise
Scientific title
The Heat-Inform Climate Chamber Trial: A Study Protocol for a Randomised Control Trial to assess the Critical Environmental Limits at 30, 35, and 40°C for Pregnant Women during Light Exercise
Secondary ID [1] 314578 0
Nil known
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Pregnancy 337683 0
Heat strain 337684 0
Condition category
Condition code
Reproductive Health and Childbirth 334018 334018 0 0
Normal pregnancy

Intervention/exposure
Study type
Interventional
Description of intervention(s) / exposure
360 women will each complete 3 trials (at 3 timepoints in their pregnancy: early 2nd, late 2nd, and early 3rd trimester), with each woman randomised to one of three environmental conditions (30, 35 or 40°C). All 3 trials for a participant will be conducted at the same temperature. Each trial will be conducted inside our climate chamber (Thermal Ergonomics Laboratory, University of Sydney, Camperdown) which has been purpose-built for the humidity ramp protocol (the gradual increase of humidity at a set temperature) required to obtain the critical environmental limit for a given study participant. Humidity will be increased at a rate of 0.5-2% Relative Humidity per minute (depending on the temperature condition- with a slower rate for higher temperatures). The primary outcome will be the humidity threshold for thermal compensability, at which the critical environmental limit is identified. Core temperature, local sweat rate, cardiovascular responses, and fetal heart rate (for pregnant participants) will be continuously monitored to determine the thresholds for heat strain. For the duration of the 60 minute trial, participants will cycle on a recumbent cycle at an intensity relative to their body size (watts per m^2), and within the bounds of 'light physical activity'. Intensity will be monitored by Borg RPE and oxygen consumption monitoring via COSMED system.
The intervention will be delivered by an exercise scientist/exercise physiologist, with supervision of a research midwife.
Intervention code [1] 331203 0
Treatment: Other
Comparator / control treatment
90 out of 360 women will be non-pregnant, and also be randomised into the three environmental conditions (30, 35, 45°C).
Control group
Active

Outcomes
Primary outcome [1] 341679 0
Critical Humidity Threshold for Compensability
Timepoint [1] 341679 0
End-of-trial for each trial (3x per participant in total).
Secondary outcome [1] 448321 0
Maximum Skin Wettedness
Timepoint [1] 448321 0
End-of-trial for all three trials in each participant.
Secondary outcome [2] 448663 0
Core temperature
Timepoint [2] 448663 0
Continuous monitoring for trial duration (3x per participant in total).
Secondary outcome [3] 448664 0
Sweat rate
Timepoint [3] 448664 0
Continuous monitoring for trial duration (3x per participant in total).
Secondary outcome [4] 448665 0
Skin Temperature
Timepoint [4] 448665 0
Continuous monitoring for trial duration (3x per participant in total).
Secondary outcome [5] 448666 0
Fetal heart rate
Timepoint [5] 448666 0
Assessed every 10 minutes for entire trial duration (3x per participant in total).
Secondary outcome [6] 448667 0
Maternal heart rate
Timepoint [6] 448667 0
Continuous monitoring for trial duration (3x per participant in total).

Eligibility
Key inclusion criteria


If Non-pregnant:
1. Between the ages of 18-40 years
2. Body mass index greater or equal to 20
3. Cleared for moderate-intensity exercise

If pregnant:
1. Between the ages of 18-40 years
2. Body mass index greater or equal to 20
3. No more than 5 units (50 ml pure alcohol) per week) since becoming pregnant.
4. No more than one miscarriage in the two previous consecutive pregnancies.
5. No previous baby delivered preterm (<37+0 weeks of gestation) or with a birthweight 4500 g.
6. No previous neonatal or fetal death, previous baby with any congenital malformations, and no evidence in present pregnancy of congenital disease or fetal anomaly.
7. No previous pregnancy affected by pre-eclampsia/eclampsia, HELLP syndrome or a related pregnancy-associated condition.
8. No clinically significant atypical red cell alloantibodies.
9. Negative urinalysis.
10. Systolic blood pressure <140 mmHg and diastolic blood pressure <90 mmHg.
11. No diagnosis or treatment for anaemia during this pregnancy (haemoglobin levels will be monitored throughout pregnancy).
12. No clinical evidence of any other sexually transmitted diseases, including syphilis and clinical trichomoniasis.
13. Not in an occupation with risk of exposure to chemicals or toxic substances, or very physically demanding activity to be evaluated by local standards. Also, women should not be conducting vigorous or contact sports, such as scuba diving or similar activities.
14. Pregnant participants must be cleared for moderate-intensity exercise from the healthcare professional that is in charge of their pregnancy check-ups (either GP, midwife or obstetrician).
Minimum age
18 Years
Maximum age
40 Years
Sex
Females
Can healthy volunteers participate?
Yes
Key exclusion criteria
1. A multiple pregnancy
2. Women whose fetus has a known major congenital abnormality.
3. Women considering not continuing the pregnancy
4. Current smoker
5. Cardiovascular disorder(s)
6. Hepatic/renal impairment(s)
7. Scheduled elective surgery (within the next 3 months)

Study design
Purpose of the study
Educational / counselling / training
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Allocation will be completed by computer and revealed to the researchers on the day of experimental trial. Participants will not be told their allocation to either 30, 35 or 45°C exposure groups.
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Permuted block randomisation by a software. Blocks will have a sample size of n = 30 (to allow for interim analyses).
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?
The people receiving the treatment/s

The people assessing the outcomes
The people analysing the results/data
Intervention assignment
Parallel
Other design features
Phase
Not Applicable
Type of endpoint/s
Efficacy
Statistical methods / analysis

Recruitment
Recruitment status
Not yet recruiting
Date of first participant enrolment
Anticipated
31/07/2025
Actual
Date of last participant enrolment
Anticipated
30/06/2028
Actual
Date of last data collection
Anticipated
22/12/2028
Actual
Sample size
Target
360
Accrual to date
Final
Recruitment in Australia
Recruitment state(s)
NSW
Recruitment hospital [1] 27995 0
Royal Prince Alfred Hospital - Camperdown
Recruitment postcode(s) [1] 44195 0
2050 - Camperdown

Funding & Sponsors
Funding source category [1] 319127 0
Charities/Societies/Foundations
Name [1] 319127 0
Wellcome Trust
Country [1] 319127 0
United Kingdom
Primary sponsor type
University
Name
The University of Sydney
Address
Country
Australia
Secondary sponsor category [1] 321591 0
None
Name [1] 321591 0
Address [1] 321591 0
Country [1] 321591 0

Ethics approval
Ethics application status
Approved
Ethics committee name [1] 317720 0
Sydney Local Health District Ethics Review Committee (RPAH Zone)
Ethics committee address [1] 317720 0
Ethics committee country [1] 317720 0
Australia
Date submitted for ethics approval [1] 317720 0
06/02/2024
Approval date [1] 317720 0
26/03/2024
Ethics approval number [1] 317720 0
2023/ETH02765

Summary
Brief summary
Trial website
Trial related presentations / publications
Public notes

Contacts
Principal investigator
Name 141930 0
Prof Adrienne Gordon
Address 141930 0
Charles Perkins Centre, The University of Sydney, Camperdown, Sydney, NSW 2050
Country 141930 0
Australia
Phone 141930 0
+61 02 9515 8248
Fax 141930 0
Email 141930 0
[email protected]
Contact person for public queries
Name 141931 0
Megan Tiong
Address 141931 0
Susan Wakil Health Building, Western Avenue, The University of Sydney, Camperdown, Sydney, NSW 2050
Country 141931 0
Australia
Phone 141931 0
+61 424862997
Fax 141931 0
Email 141931 0
[email protected]
Contact person for scientific queries
Name 141932 0
Megan Tiong
Address 141932 0
Susan Wakil Health Building, Western Avenue, The University of Sydney, Camperdown, Sydney, NSW 2050
Country 141932 0
Australia
Phone 141932 0
+61 424862997
Fax 141932 0
Email 141932 0
[email protected]

Data sharing statement
Will the study consider sharing individual participant data?
No


What supporting documents are/will be available?

No Supporting Document Provided


Results publications and other study-related documents

Documents added manually
No documents have been uploaded by study researchers.

Documents added automatically
No additional documents have been identified.