Staying Safe in the Heat During Pregnancy: What You Need to Know
Staying well hydrated is one of the most important things you can do for yourself and your baby during hot weather
Hot weather and pregnancy do not always sit comfortably together. Your body is already working harder than usual to support your growing baby, and rising temperatures add an additional layer of physical demand. You feel the heat more intensely during pregnancy, you sweat more, your feet and ankles are more likely to swell, and your risk of dehydration is higher than it would be outside of pregnancy. None of this means you cannot enjoy the summer, but it does mean taking a few straightforward precautions that can make a significant difference to how you feel and, in some cases, to the safety of your pregnancy.
Why pregnancy makes you more vulnerable to heat
Pregnancy increases your basal metabolic rate, meaning your body generates more heat at rest than it normally would. Your blood volume increases by around 50 per cent during pregnancy, and your cardiovascular system works continuously to supply the placenta. In hot weather, your body diverts blood flow to the skin in order to cool itself down, which can reduce the supply available to your muscles, brain, and other organs, leaving you feeling faint, dizzy, or exhausted far more quickly than you might expect.
Your core body temperature also matters for your baby. The placenta does not have its own cooling mechanism, and a sustained rise in your core temperature, particularly in the first trimester, has been associated with an increased risk of neural tube defects. Later in pregnancy, overheating can contribute to reduced fetal movement and, in severe cases, premature labour. These risks are not inevitable, and most women navigate hot summers perfectly safely, but they are the reason that heat awareness in pregnancy is taken seriously clinically.
Please note: The information in this article is intended as general guidance. If you experience dizziness, fainting, a significant reduction in your baby's movements, strong contractions, or feel unwell in hot weather, contact your midwife, consultant, or maternity unit promptly rather than waiting to see whether symptoms resolve on their own.
Staying hydrated: the single most important thing you can do
Dehydration during pregnancy can cause headaches, dizziness, constipation, and urinary tract infections. In more significant cases it can trigger uterine contractions and reduce amniotic fluid levels. The good news is that it is entirely preventable with consistent attention to fluid intake.
- Aim for at least 8 to 10 glasses of water per day in normal conditions, and increase this in hot weather or if you are being physically active. Do not wait until you feel thirsty, as thirst is a late sign of dehydration.
- Carry water with you at all times. A large reusable bottle that you can refill throughout the day makes it much easier to keep track of how much you are drinking.
- Flavour your water if plain water feels unappealing. Slices of cucumber, lemon, or mint can make it easier to drink enough without resorting to sugary drinks or excessive caffeine.
- Eat water-rich foods. Fruits and vegetables such as watermelon, cucumber, strawberries, and lettuce all contribute to your overall fluid intake and are cooling and nutritious.
- Monitor the colour of your urine. Pale straw yellow indicates good hydration. Dark yellow or amber is a clear sign to drink more immediately.
- Limit caffeine and sugary drinks, both of which can contribute to dehydration. Caffeine intake during pregnancy should be kept to under 200mg per day regardless of the weather.
Practical ways to keep cool
Reducing your exposure to heat and helping your body to manage temperature is the foundation of staying comfortable during a hot spell in pregnancy.
- Stay indoors during the hottest part of the day, which is typically between 11am and 3pm. If you need to go out, try to do so in the morning or evening when temperatures are lower.
- Use fans and open windows strategically. During the day, keep blinds or curtains closed on south-facing windows to prevent rooms from heating up. Open windows on opposite sides of the house in the evening to create a through-draught.
- Cool your pulse points. Applying a cold, damp cloth or running cool water over your wrists, inner elbows, the back of your neck, and your ankles is a quick and effective way to lower your body temperature.
- Take cool showers or baths. These do not need to be cold, just comfortably cool. Avoid very cold water as this can cause blood vessels to constrict and may actually trap heat in the body.
- Wear loose, lightweight, breathable clothing. Natural fabrics such as cotton and linen allow air to circulate and moisture to evaporate from the skin. Avoid synthetic fabrics which trap heat.
- Sleep with a light sheet rather than a duvet, and consider placing a hot water bottle filled with cold water at the foot of your bed. Cooling your feet helps lower your overall body temperature during the night.
- Use a portable fan or misting fan when out and about. Small battery-powered fans are inexpensive and genuinely effective at keeping you comfortable.
Avoid hot tubs, saunas, and steam rooms entirely during pregnancy. These raise your core body temperature rapidly and significantly, and are not safe at any stage of pregnancy. Even a short session can bring your core temperature to a level that poses a risk to your baby.
Swelling in the heat
Swelling of the feet, ankles, and hands is extremely common in pregnancy and tends to worsen considerably in hot weather. This happens because heat causes blood vessels to dilate, and the increased blood volume of pregnancy means more fluid leaks into the surrounding tissues. It is uncomfortable but in most cases entirely normal.
To manage swelling in the heat:
- Avoid standing for long periods. If you need to stand, try to shift your weight regularly and take sitting breaks as often as possible.
- Elevate your feet whenever you are sitting or resting, ideally above the level of your hips.
- Wear supportive, comfortable footwear that accommodates any swelling. Many women go up a shoe size during pregnancy, particularly in hot weather.
- Consider wearing compression stockings, particularly if you are travelling or spending a long time on your feet. These help to prevent fluid from pooling in the lower legs.
- Avoid tight clothing or jewellery around the ankles and wrists.
- Continue drinking plenty of water. Counterintuitively, good hydration helps to reduce fluid retention.
Seek prompt medical advice if swelling comes on suddenly, is severe, or is accompanied by a headache, visual disturbances, or pain under your ribs. These can be signs of pre-eclampsia, which is a serious condition that requires immediate assessment. Do not wait to see if it settles.
Sun safety in pregnancy
Pregnancy makes your skin more sensitive to UV radiation than usual, partly due to hormonal changes. This increases your risk of sunburn and also of a condition called chloasma, or the mask of pregnancy, where patches of darker pigmentation develop on the face. These patches can be made significantly worse by sun exposure and may persist for some time after delivery.
- Apply a broad-spectrum sunscreen of at least SPF 30, and ideally SPF 50, to all exposed skin. Reapply every two hours and after swimming or sweating.
- Wear a wide-brimmed hat to protect your face, neck, and shoulders, which are the areas most commonly affected by pregnancy-related pigmentation.
- Seek shade, particularly during the hottest part of the day. A combination of shade and sunscreen is more effective than either alone.
- Wear UV-protective sunglasses to protect your eyes. Hormonal changes in pregnancy can also make your eyes more sensitive to light.
Most standard sunscreens are safe to use in pregnancy. Mineral-based sunscreens containing zinc oxide or titanium dioxide are generally considered the safest option and are widely available. If you have any concerns about a specific product, your pharmacist or midwife can advise.
Exercise in hot weather
Staying active during pregnancy is beneficial for both physical and mental wellbeing, but exercising in high temperatures requires some adjustments to keep you and your baby safe.
- Exercise in the coolest part of the day, either early morning or evening. Avoid exercising outdoors at midday or in the afternoon during a heatwave.
- Choose indoor activities such as swimming, pregnancy yoga, or gentle gym sessions in air-conditioned spaces during particularly hot spells.
- Swimming is an excellent choice in hot weather as the water helps to keep your body temperature regulated whilst providing a low-impact cardiovascular workout.
- Reduce the intensity of your usual exercise in hot weather. Your heart rate rises more quickly in the heat during pregnancy, and pushing yourself as hard as you might normally is not safe.
- Hydrate before, during, and after exercise. Drink water before you start, take regular sips during activity, and rehydrate thoroughly afterwards.
- Stop and rest if you feel dizzy, breathless, faint, or overheated. These are signals that your body needs a break, and they should not be ignored during pregnancy.
Travel in hot weather
Hot weather travel, whether by car, public transport, or plane, presents additional challenges during pregnancy. Being confined and unable to move freely makes it harder to regulate your temperature and increases the risk of blood clots, which are already elevated in pregnancy.
- On long car journeys, stop regularly to walk around and stretch your legs. Keep the air conditioning on and have water to hand at all times.
- On public transport, do not hesitate to ask for a seat, particularly in hot and crowded conditions. Many transport operators in the UK provide priority seating for pregnant women, and wearing a Baby on Board badge can make it easier to be offered a seat.
- On flights, drink plenty of water, avoid alcohol, walk the aisle regularly, and wear compression stockings. Most airlines are happy for pregnant women to fly up to 36 weeks on a single pregnancy, though you should check your airline's policy and carry a letter from your midwife or consultant if you are beyond 28 weeks.
- Avoid travelling to destinations with extreme heat or limited access to clean water and medical facilities during the third trimester. If you are planning international travel, discuss it with your consultant in advance.
Warning signs to act on immediately
Most discomfort in hot weather during pregnancy is manageable and resolves with rest, fluids, and cooling measures. However, some symptoms require prompt medical attention.
Contact your midwife or maternity unit if you experience
- A significant reduction in your baby's movements
- Strong, regular contractions before 37 weeks
- Sudden or severe swelling of the face, hands, or feet
- A severe headache that does not settle with rest and paracetamol
- Visual disturbances such as flashing lights or blurred vision
- Pain or a feeling of pressure under your ribs
- Persistent vomiting that is preventing you from keeping fluids down
Call 999 or go to your nearest emergency department if you experience
- Loss of consciousness or fainting that does not resolve quickly
- Signs of heat stroke such as a very high temperature, confusion, rapid breathing, or hot dry skin without sweating
- Chest pain or difficulty breathing
- Signs of a blood clot such as a swollen, painful, red leg or sudden breathlessness
Heat exhaustion and heat stroke are medical emergencies. Heat exhaustion presents with heavy sweating, cold and clammy skin, a fast but weak pulse, nausea, and muscle cramps. If it progresses to heat stroke, sweating stops, the skin becomes hot and dry, and confusion sets in. At this point you need emergency medical help immediately. Cool the person down by any means available whilst waiting for the ambulance.
A note on newborns in the heat
If you have recently given birth and are caring for a newborn during hot weather, it is worth knowing that babies cannot regulate their body temperature in the same way adults can. They cannot tell you they are too hot, and they cannot remove their own clothing or move away from the heat. Overheating in newborns is a known risk factor for sudden infant death syndrome (SIDS).
- The ideal room temperature for a sleeping baby is between 16 and 20 degrees Celsius.
- Dress your baby in a single layer of light, breathable clothing in hot weather. A vest or a light babygrow is usually sufficient.
- Do not use fans pointed directly at your baby, and keep them out of direct sunlight at all times.
- Check your baby regularly for signs of overheating: feeling hot to the touch on the chest or back of the neck, looking flushed, and being unusually unsettled.
- Do not put sunscreen on babies under six months. Keep them in the shade and covered with lightweight clothing and a hat instead.
- If you are breastfeeding, your baby may want to feed more frequently in the heat. This is normal and helps to keep them hydrated.
Frequently asked questions
Brief, moderate sun exposure is generally fine, but prolonged sunbathing in high temperatures is not recommended during pregnancy. Lying flat on your back in the sun for extended periods can raise your core body temperature, increase your risk of sunburn and pigmentation changes, and in the second and third trimesters can compress the vena cava, reducing blood flow. Enjoy the sunshine with appropriate shade, sunscreen, and plenty of water, but avoid baking in the heat for long stretches.
Yes. Dehydration is a recognised trigger for Braxton Hicks contractions, and in some cases can contribute to preterm labour. If you experience regular or painful contractions and suspect you may be dehydrated, drink water, rest, and contact your midwife or maternity unit if the contractions do not settle within an hour or if they are occurring before 37 weeks.
In normal conditions, aiming for around 8 to 10 glasses of water per day is a reasonable starting point during pregnancy. In hot weather, or if you are physically active, you will need more. A practical guide is to monitor the colour of your urine: pale straw yellow suggests you are well hydrated, whilst anything darker indicates you need to drink more. Do not wait until you feel thirsty, as thirst is a late indicator of dehydration.
Yes, swimming in a properly maintained pool is one of the safest and most beneficial forms of exercise during pregnancy. The water supports your weight, reduces pressure on your joints, and helps to regulate your body temperature. It is particularly valuable in hot weather. Avoid very cold water, which can cause blood vessels to constrict suddenly, and avoid crowded lanes where you might be at risk of a bump to the abdomen.
Feeling faint in the heat is very common in pregnancy. Hot weather causes blood vessels to dilate and blood to pool in the lower limbs, temporarily reducing the supply to the brain. This effect is amplified in pregnancy because your cardiovascular system is already working harder than usual. Avoid standing for long periods, particularly in hot or crowded environments, change positions slowly, stay well hydrated, and sit or lie down immediately if you feel faint. If fainting is frequent or severe, mention it to your midwife or consultant.
Yes, paddling pools are a perfectly safe way to cool down in pregnancy. Sitting or standing with your feet and ankles in cool water is particularly effective and helps to reduce swelling as well as lower your overall body temperature. Avoid very cold water, which can cause a sudden shock response, and ensure the pool is clean and changed regularly to avoid infection risk.
You should always take a reduction in your baby's movements seriously, regardless of the weather. There is no safe threshold below which reduced movement can be ignored. If you notice your baby is moving less than usual, drink a cold glass of water, lie on your left side, and count movements for an hour. If you are not reassured, contact your midwife or maternity unit straight away. Do not wait until the next day.
Mr Myriknas practices at The Kensington Wing and The Chelsea Wing within Chelsea and Westminster Hospital, located at 369 Fulham Road, London SW10 9NH. He also holds an NHS Consultant post at Chelsea and Westminster NHS Foundation Trust, which encompasses both Chelsea and Westminster Hospital and West Middlesex University Hospital.
Final thoughts
Hot weather during pregnancy is entirely manageable with the right approach. Staying hydrated, keeping cool, knowing your limits with exercise and sun exposure, and being alert to the warning signs that need medical attention will see most women through even the warmest of summers safely and comfortably.
The key principle is to listen to your body. Pregnancy is not the time to push through discomfort in the heat. Rest when you need to, drink more than you think you need to, and do not hesitate to seek advice if something does not feel right. Your midwife and consultant are there precisely for those moments of uncertainty.
If you have any concerns about your wellbeing during hot weather, or if you would like to discuss your pregnancy care with Mr Myriknas, please visit our private maternity services page or contact us directly.