None listed
Conditions
Brief summary
Using a randomised controlled trial study design, 270 pregnant and 90 non-pregnant women will complete cycling trials in a climate chamber with increasing humidity at three fixed ambient temperatures (30°C, 35°C, and 40°C). 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. We will hence seek to quantify critical environmental limits (of temperature and humidity) in pregnant women compared to non-pregnant women during light physical activity. Lay hypothesis: Our study hypothesis is that the critical humidity before core temperature rises, will be lower for women in later stages of pregnancy regardless of ambient temperature.
Interventions
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
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.
Sponsors
The University of Sydney
Study design
Allocation
Randomised controlled trial
Intervention model
Parallel
Primary purpose
Diagnosis
Masking
Blinded (masking used) (Subject, Investigator, Outcomes Assessor)
Eligibility
Sex/Gender
All
Age
18 Years to 40 Years
Healthy volunteers
Yes
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).
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)
Outcome results
None listed