Women can safely take short hot baths or saunas while pregnant without harming their unborn baby, a review has found.
Health professionals recommend mothers-to-be take warm baths, particularly early on in pregnancy, to avoid risk of miscarriage or early birth.
Raising body temperature too high can lead to a drop in blood pressure, which carries a risk of reducing the amount of oxygen and nutrients a baby can get.
Researchers from the University of Sydney looked at how activities such as baths – at 40C – and saunas – at 70C – for 20 minutes pushed up core body temperatures.
Women can safely take short hot baths or saunas while pregnant without harming their unborn baby, a review has found
They also looked at how exercising in warm environments, such as aqua aerobics, affected a woman’s body temperature.
The researchers found that no woman exceeded the recommended core temperature limit of 39C, suggesting experts are being overcautious.
They analysed the results of 12 studies, involving 347 pregnant women at various stages of pregnancy, in response to heat stress either through exercise or through passive heating.
Responses were measured according to intensity and duration of exercise as well as ambient temperature and humidity.
They found the highest average core temperature was 36.9C for hot water bathing and 37.6C for sauna exposure as well as was 38.3C for exercise in water.
As a result, women can sit in hot baths or saunas for 20 minutes, irrespective of what stage of pregnancy they are at, they say.
The authors also said women can do up to 35 minutes of high intensity aerobic exercise at air temperatures of up to 25C and aqua-aerobic exercise in water temperatures ranging from 28.8C to 33.4C for up to 45 minutes.
Health professionals recommend mothers-to-be take warm baths, particularly early on in pregnancy, to avoid risk of miscarriage or early birth
The findings contradict current advice that pregnant women should avoid heat stress based on concerns about possible risks of exceeding a core body temperature during pregnancy.
Pregnant women can safely exercise in warm weather and take short hot baths or saunas without risking critical elevations in body temperature that could harm their unborn child.
The Royal College of Obstetricians and Gynaecologists advises that pregnant women do up to 30 minutes a day of aerobic exercise – such as running, swimming or dancing.
It recommends that exercising in water, for example, at an antenatal class, that the temperature of the water shouldn’t be above 32C (89.6F).
Pregnant women can safely exercise in warm weather and take short hot baths or saunas without risking critical elevations in body temperature that could harm their unborn child
It says that the hormonal changes in the body can make expectant mothers feel faint more often and suggests avoiding situations where they could get too hot, such as sitting in a jacuzzi, steam room or using a hot tub.
Dr Virginia Beckett, consultant obstetrician and spokesman for the Royal College of Obstetricians and Gynaecologists (RCOG), said: ‘The current NHS guidelines recommend avoiding the use of saunas, jacuzzis and steam rooms during pregnancy because of the risks of overheating, dehydration and fainting – pregnant women are already at an increased risk of fainting due to hormonal changes.
‘While this new study did not find a rise in core temperature of up to the recommended limit of 39C in 347 pregnant women exposed to heat stress, either through exercise or through passive heating, such as using a sauna or sitting in a hot bath, we continue to recommend that pregnant women follow NHS advice and take care when exercising and being in warm temperatures by drinking plenty of water before and after and not exhausting themselves. If women experience any unusual symptoms or feel unwell, they stop exercising and contact a healthcare professional immediately.’
‘There are many health benefits to keeping active during pregnancy and we strongly encourage women to exercise while pregnant. Contact sports where there is a risk of being hit in the abdomen should be avoided and women with a medical condition, or who have not exercised before pregnancy, should seek advice from their doctor or midwife before exercising.’