If you spend too long in a spa pool, hot pool, hot tub or sauna while you are pregnant, you are at risk of overheating, getting dehydrated and fainting. You are more likely to faint because of the changes in your blood pressure and blood volume due to being pregnant.
When you use a sauna, hot pool, spa pool or hot tub, your body cannot lose heat effectively by sweating. This can cause your body's core temperature to rise and you to become overheated. Some people choose to avoid spa pools and saunas while pregnant. If you do use a spa pool or sauna, do not spend too long in there and if you feel uncomfortable, then you should get out. To help keep from getting too warm in a hot tub, sit with your arms and chest above the water.
If you overheat, more blood flows close to your skin to help cool your body by sweating. This means there is less blood flow to your internal organs, such as your brain. If you do not get enough blood and oxygen to your brain, it can make you feel faint.
When you are pregnant, the hormonal changes in your body can make you feel faint more often. This is why you may want to avoid situations where you could get too hot, such as sitting in a spa pool or sauna.
If you are exercising in water, such as at an antenatal class, the temperature of the water should not be above 32°C. If you are using a hydrotherapy pool, the temperature should not be above 35°C. Some hot tubs can be as hot as 40°C, which is why it is best to avoid them.