Pregnancy – body temperature

You are likely to feel warmer than usual during pregnancy. This is due to hormonal changes and an increase in blood flow to your skin. You may also sweat more. These changes are not harmful, but may make you feel uncomfortable.

If you are feeling uncomfortable, it may help if you:

• wear loose clothing made of natural fibres, as these are more absorbent and breathable than synthetic fibres
• keep your room cool – you could use an electric fan
• wash frequently to help feel fresh.

A fever is when your core body temperature is more than 38°C (degrees Celsius). The most common cause of a fever is a viral infection. A bacterial infection is a less common but more serious cause. Read more about fever. 

If you have a fever of over 38°C for longer than a day, contact your midwife or doctor for advice.

If you have a fever, you can safely take paracetamol in pregnancy to reduce your temperature. You should not take non-steroidal anti-inflammatory medications (NSAIDs) such as ibuprofen (Brufen) or diclofenac (Voltaren). You should keep hydrated by drinking fluids such as water.

Usually a fever does not have any effect on your pregnancy. An untreated fever can increase the chance of pregnancy complications. The complications are more likely to be caused by the underlying cause of the fever, such as bacterial infection, rather than the fever itself.

A fever caused by an infection does not usually cause harm to your baby. However, very occasionally it may cause other problems, such premature labour or serious infection in the mother. If you are concerned, you should contact your doctor or midwife.

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. 

Feeling faint

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. 

Water temperature

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. 

You are encouraged to exercise while pregnant. However, you should avoid becoming overheated, particularly in the first trimester or when you are planning a pregnancy. Drink plenty of water, and wear loose-fitting clothing. Do not exercise outside when it is very hot or humid. Read more about pregnancy and exercise.