Overheating and Dehydration in Pregnancy

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Coming soon to a sky near you – heatwaves and brightly shining sun. Regardless of what hemisphere you live in, temperatures are rising. Whether or not you believe in global warming, you are undoubtedly more aware of hotter temperatures now that you are pregnant. During pregnancy, your body’s lower threshold for heat and dehydration can mean trouble for you and your baby. Keep reading to learn more about the signs and symptoms of dehydration and overheating during pregnancy and how to keep your cool.

What is overheating, and why does it happen more in pregnancy?

Overheating happens whenever your body temperature goes above its normal 98.6 degrees Fahrenheit (37 degrees Celsius). Pregnant women overheat more easily because their core temperatures are already higher than when not pregnant. Another reason you feel like you are a furnace is because growing a baby requires a lot of energy – and produces a lot of energy, released as heat.

Hormonal changes, especially early in pregnancy, can cause overheating and even night sweats or hot flashes during pregnancy. When you are pregnant, you need more blood to bring oxygen and nutrients to your baby, but this increase in blood volume acts like radiant heat floors to keep you extra toasty. Your heart must beat faster to move this extra blood, pumping up your metabolism and turning you into a furnace.

Ideally, for your health and your baby’s health, your core internal temperature (aka the one you measure with a thermometer) should stay below 102 degrees Fahrenheit (39 degrees Celsius). If your thermometer goes above this number, it is time to be giving your OB a call.

It is more challenging for you to give off this heat and cool down effectively when pregnant. Unfortunately, this means that the chores you used to tolerate at warmer temperatures may no longer be safe for you while pregnant. The same is true for those intense workouts or Bikram yoga classes – temperatures and levels of exertion safe before pregnancy may now be too much in your gestational state.

What are the signs of overheating?

Swelling, sweating, crankiness, a mouth as dry as a dessert, and feeling like you could  spontaneously combust are all clues that you might be on your way to overheating. Other signs of overheating are:

  • Warm skin
  • Headache
  • Dizziness
  • Nausea
  • Muscle cramps

If you can’t cool down, overheating can progress to heat exhaustion and heat stroke, two types of heat-related illnesses. With heat exhaustion, you may notice your pulse racing and bucket-loads of sweat.

If you suspect that you are beginning to overheat, stop all activity, find an air-conditioned place, and lie on your left side. Try to have a fan or air conditioner moving air over you. Sip cool water and try to rest. Call your provider if:

  • You don’t feel better within a half an hour of resting
  • Your symptoms get worse
  • You are not feeling your baby move if you are further than 20 weeks in your pregnancy.

If untreated, heat exhaustion can progress to heatstroke, a medical emergency. With heat stroke, your internal core temperature rises so high that your organs and body systems can’t work the way they are supposed to. People can die from heat stroke if not treated right away.

What is dehydration?

Dehydration happens when your body loses more water than what you can replace through drinking. The most common causes of dehydration during pregnancy are:

  • Getting sick with a stomach or intestinal bug that causes vomiting and diarrhea
  • Overheating
  • Morning sickness or hyperemesis
  • Over-exercising (too intensely or for too long)
  • Fever
  • Not drinking enough water
  • Air travel

What are the signs of mild dehydration in pregnancy?

The first sign of dehydration is feeling thirsty. Other signs to look for are:

  • Overheating
  • Chapped lips
  • Dry mouth
  • Headache
  • Sleepiness
  • Needing to pee less often
  • Constipation

Watching for these early warning signs will help keep you from becoming more severely dehydrated.

What are the signs of severe dehydration in pregnancy?

If you have ignored the early warning signs of mild dehydration you may notice some of these other symptoms such as:

The signs and symptoms of mild and severe dehydration are similar to many normal changes in pregnancy. That’s why dehydration and overheating can sneak up on you – meaning that you may need to pay closer attention to how much water you are drinking, your number of bathroom breaks in a day, and the color of your pee to stay healthy. This is especially true if you have to work outside or in a hot environment or you will be pregnant during hotter seasons.

Why is water so important to a healthy pregnancy?

Your body and your growing baby need water.  Water is an essential ingredient for normal fetal growth and pregnancy health. Your body needs water to:

  • Increase the amount of blood you have in your body (blood volume)
  • Produce sweat to help keep you cool by lowering your internal temperature
  • Fuel your higher metabolic rate of pregnancy (providing energy for you and your baby)
  • Keep the right amount of amniotic fluid (your baby’s private swimming pool for nine months).

The higher metabolic rate of pregnancy means that you need more oxygen and need to blow off more carbon dioxide by exhaling. So, pregnant people breathe in and out more times in a minute than non-pregnant people. But unfortunately, each time you breathe in and out, you lose more water through evaporation.

No one likes to make hourly trips to the bathroom or wait with an uncomfortably full bladder through a Zoom call, so some pregnant women may limit how much water they drink. Unfortunately, this can put them at risk for dehydration and overheating. Instead, try to embrace your trips to the bathroom as positive feedback for a job well done – your frequent pee breaks with clear urine mean that you are well-hydrated.

How does being dehydrated or overheated harm your pregnancy?

Studies show that the extreme heat and humidity caused by global warming are harmful to pregnant people. When you are dehydrated, you can’t produce sweat. Sweat is your body’s primary defense against overheating. When you are dehydrated, you overheat and experience heat stress. Heat stress (when your body rises to104 degrees Fahrenheit or higher) has been shown to increase your risk for:

While these findings can seem scary, they don’t mean that you need to stay locked in an air-conditioned room for the entire nine months of your pregnancy. Instead, you can stay healthy and cool by slightly adjusting your routine, being diligent about drinking at least 12 cups (96 ounces) of water every day, and tuning into the weather report regularly.

How do you avoid dehydration and overheating when it’s hot, and you’re pregnant?

While you might be considering renting a North Pole igloo after reading this post, taking these common-sense steps can keep you and your baby safe from dehydration and overheating.

  • Drink plenty of water and other fluids (non-caffeinated and non-sugar-sweetened beverages are your best choice)
  • Check local news or the internet for weather information and heat updates – look for information about the heat index, UV index, humidity, and air quality rating.
  • Don’t exercise outside when it’s very hot or humid. If you do go outdoors, avoid the hottest hours of the day (10 a.m. – 5 p.m.).
  • Wear loose-fitting, light-colored clothing and a wide brimmed hat outdoors on warmer, sunnier days.
  • Take cool-down breaks if you work in a hot environment. Seek out shaded and air-conditioned work conditions.
  • Use air conditioning. If you don’t have access to air conditioning in your home, take refuge at cooling centers, malls, and libraries.
  • Take frequent cool showers or baths to cool off. Drip dry in front of a fan or air conditioner for the maximum cooling effect.
  • Eat light, cold foods. For example, salads and fruit are easy to digest and don’t require cooking.
Amy Harris
Amy Harris is a certified nurse-midwife with a Master's Degree in Maternal and Child Health from Harvard Chan School of Public Health. Her passions are health literacy and women's reproductive health. A recent two-year sabbatical with her family in Spain was the impetus for becoming a freelance women's health writer. An exercise nut, she is happiest outdoors and on adventures abroad.

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