Pregnant women can enjoy hot baths and saunas without raising their temperature to levels that might harm their unborn child, a new review has suggested.
Current health advice states that women who are expecting should avoid heat stress because it risks taking their core temperature beyond 102F (39C.)
Old wives tales have also traditionally recommended gin and a hot bath to get rid of unwanted pregnancies while the NHS and The Royal College of Obstetricians and Gynaecologists currently warns pregnant women to also avoid saunas and jacuzzis.
But the new review, which compiled the results of 12 studies involved 347 women, found that sitting in a sauna, exercising or enjoying a hot bath did not dangerously elevate temperature.
No woman exceeded the recommended core temperature limit of 102F (39℃) across all studies.
Researchers from the University of Sydney warn that the ban could prevent women from exercising when pregnant.
Writing in the British Journal of Sports Medicine, Dr Ollie Jay, Associate Professor in Exercise and Sports Science, said: “Health guidelines for pregnant women unanimously state that hot water immersion or sauna use should be restricted due to the elevated risk of maternal hyperthermia and the consequent potential impact on fetal development.
“However, our results suggest that heat stress risk is low.”
Based on the results. the researchers also say that pregnant women can safely engage in up to 35 minutes of high intensity aerobic exercise at 80-90 per cent of their maximum heart rate at air temperatures of up to 77F (25℃) and 45 per cent relative humidity.
They can also safely participate in aqua-aerobic exercise in water temperatures ranging from 83F (28.8C) to 92.12F (33.4C) for up to 45 minutes, and sit in hot baths upto 104D (40C) or hot/dry saunas upto 158F (70C) and 15% relative humidity for up to 20 minutes, irrespective of pregnancy stage.
Some studies also showed a reduction in the rise in core temperature as pregnancy progressed, lending support to the theory that thermal regulation is enhanced in later trimesters. While the underlying reason for this is unclear, the researchers suspect it may be linked to changes in body mass and surface area.
The researchers say that more studies are needed to identify safe exposure and environmental limits for pregnant women who are physically active in hotter climates, but say their results suggest that heat stress risk is low.