High body temperature during pregnancy

Being pregnant in the summer can be challenging. We discuss the risks of hot weather and high body temperature during pregnancy, and how to beat the heat.

Some mums-to-be find being pregnant in the summer months a challenge due to the hot weather. If a pregnant women’s core body temperatures rises too high, her baby has a slightly higher risk of complications that could affect their development or lead to birth defects.

So it’s important to take it easy and stay cool when pregnant. This is especially true during a heatwave when there is a greater risk of dehydration, heat exhaustion and heatstroke.

Rachel Heathcock, NCT Antenatal Teacher, offers her tips to pregnant women on keeping cool in the hot weather, in this video.

High body temperature in pregnancy

Many women say they feel hotter during pregnancy. This is despite the limited evidence to suggest pregnant women’s core body temperature is actually any higher than usual because of pregnancy (Jones et al, 1985; Clapp, 1991; Lindqvist et al 2003).

Yet warmer weather can certainly make pregnant women feel more hot and uncomfortable (Jones et al, 1985; Raines, 2018). Hot weather can also lead to dehydration, fatigue, heat exhaustion, fainting or even heatstroke, which can be fatal (NHS Choices, 2018a). So it’s really important to keep cool when pregnant.

Risks of overheating

If a pregnant woman’s body temperature rises above 39.2°C in the first 12 weeks of pregnancy, the baby has a slightly increased risk of having a birth defect (Moretti et al, 2005; RCOG, 2006). A woman’s body temperature would not typically be so high without a fever or exercising in a very hot and humid climate before acclimatising.

It’s best to avoid overexerting yourself, particularly in the first trimester of pregnancy (RCOG, 2006). If there is a sudden heatwave and it’s very hot and humid, you will need to take it easy and avoid exercising. That is, until you’ve acclimatised, which will take a few days.

Water temperature

Swimming or having a cool bath during a heatwave can help you to feel less hot and bothered. If you are having a bath, exercising in water or swimming in a pool, the water temperature shouldn’t be above 32°C. If you are using a hydrotherapy pool, the water temperature should not exceed 35°C (RCOG, 2006).

If you’re going out or are exercising in warm weather, you’ll want to be prepared. You could carry a water spray in your bag so you can spray yourself with some cold water to cool off quickly. You could also try putting your wrists under cold running water or pouring a little water from your bottle over them.

Melasma

Avoiding the sun can help prevent melasma also called pregnancy mask. Melasma is a common skin condition in which brown or grayish patches of pigmentation develop (British Association of Dermatologists, 2018). It usually develops on the face.

This condition is more common in women, especially during pregnancy. Up to 50% of women may be affected (British Association of Dermatologists, 2018).

One of the most important things to prevent melasma worsening is protecting yourself from UV radiation. You can do this by avoiding the sun, wearing a wide-brimmed hat when you are outside and by wearing sun tan lotion factor 30 or above, with a high UVA rating (British Association of Dermatologists, 2018).

Swollen ankles

Ankles, feet and fingers can swell in pregnancy, as your body retains more water than usual. It is often worse during hot weather, at the end of the day and further into your pregnancy (NHS Choices, 2018c).

Throughout the day, the extra water tends to gather in the lowest parts of the body, especially if the weather is hot or you’ve been standing a lot (NHS Choices, 2018c). The pressure of your growing womb can also affect the blood flow in your legs, which can cause fluid to build up in your legs, ankles, and feet (NHS Choices, 2018c).

If you are pregnant and experience a sudden swelling of your face, hand or feet, and a severe headache, contact your midwife, GP or NHS 111 straight away, as these could be signs of pre-eclampsia (NHS Choices, 2018c).

Heat exhaustion

Symptoms of heat exhaustion include:

  • dizziness and confusion
  • loss of appetite and feeling sick
  • excessive sweating and pale
  • clammy skin
  • cramps in arms, legs, and stomach
  • fast breathing and pulse
  • temperature of 38 degrees or above
  • intense thirst.

(NHS Choices, 2018b)

If someone shows signs of heat exhaustion, they need to be cooled down. Move them into a cool place in the shade or indoors and get them to lie down with their feet up. They should drink water to rehydrate. Cool them with a fan or cool water spray. They should start to feel better or cool down within 30 minutes (NHS Choices, 2018b).

Heatstroke

Heatstroke is a medical emergency and can be fatal if not treated quickly.

Call 999 if the person:

  • is no better after 30 minutes
  • feels hot and dry
  • is not sweating even though they are too hot
  • has a temperature that's risen to 40°C or above
  • is breathing rapidly or has shortness of breath
  • is confused
  • has a fit (seizure)
  • loses consciousness
  • is unresponsive.

(NHS Choices, 2018b)

This page was last reviewed in April 2018

Further information

Our support line offers practical and emotional support with feeding your baby and general enquiries for parents, members and volunteers: 0300 330 0700.

We also offer antenatal courses which are a great way to find out more about birth, labour and life with a new baby.

Make friends with other parents-to-be and new parents in your local area for support and friendship by seeing what NCT activities are happening nearby.

The British Red Cross have useful information about coping in the heat.

Read more about heat exhaustion and heat stroke from NHS Choices.

British Association of Dermatologists (2018). Melasma. Available from: http://www.bad.org.uk/for-the-public/patient-information-leaflets/melasma/?showmore=1&returnlink=http%3A%2F%2Fwww.bad.org.uk%2Ffor-the-public%2Fpatient-information-leaflets#.WuYs9yMrLPA [Accessed 1st April 2018]

Clapp III JF. (1991) The changing thermal response to endurance exercise during pregnancy. American journal of obstetrics and gynecology. 165(6):1684-1689. Available from: https://www.ncbi.nlm.nih.gov/pubmed/1750460 [Accessed 1st April 2018]

Jones RL, Botti, JJ, Anderson WM, Bennett NL. (1985) Thermoregulation during aerobic exercise in pregnancy. Obstetrics and Gynecology. 65(3):340-345. Available from: https://www.ncbi.nlm.nih.gov/pubmed/3974960  [Accessed 1st April 2018]

Lindqvist PG, Marsal K, Merlo J, Pirhonen JP. (2003) Thermal response to submaximal exercise before, during and after pregnancy: a longitudinal study. The Journal of Maternal-Fetal & Neonatal Medicine. 13(3):152-156. [Accessed 1st April 2018]

Moretti, ME, Bar-Oz B, Fried S, Koren G. (2005) Maternal hyperthermia and the risk for neural tube defects in offspring: systematic review and meta-analysis. Epidemiology. 16(2):216-219. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15703536  [Accessed 1st April 2018]

NHS Choices. (2018a) Dehydration. Available from: https://www.nhs.uk/conditions/dehydration/ [Accessed 1st April 2018]

NHS Choices. (2018b) Heat exhaustion and heatstroke. Available from: https://www.nhs.uk/conditions/heat-exhaustion-heatstroke/  [Accessed 1st April 2018]

NHS Choices. (2018c) Swollen ankles, feet, and fingers in pregnancy. Available from: https://www.nhs.uk/conditions/pregnancy-and-baby/swollen-ankles-feet-pregnant/  [Accessed 1st April 2018]

Raines D. (2018) Is it normal for a pregnant woman’s body temperature to rise? Available from: https://www.sharecare.com/health/fertility-pregnancy-childbirth/normal-pregnant-womans-body-temp-to-rise [Accessed 1st April 2018]

RCOG. (2006) Recreational exercise and pregnancy: information for you. Available from: https://www.rcog.org.uk/globalassets/documents/patients/patient-information-leaflets/pregnancy/recreational-exercise-and-pregnancy.pdf [Accessed 1st April 2018]

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