During the dogs of summer, you may prefer to stay indoors when exercising. However, if you enjoy the heat or prefer outdoor activities – such as running, cycling, hiking, etc. – you may be wondering if you can exercise safely in the heat during pregnancy. Besides, if you’re pregnant, you’ve probably been told to minimize heat exposure and avoid things like saunas, hot baths, and exercise in the heat.
But why is that? Where does the caution about heat exposure during pregnancy come from and how do you ensure your preferred form of physical activity is safe?
This article will help you understand the basis for concern about overheating during pregnancy, provide you with the latest research on this topic and, most importantly, provide simple guidelines to help you stay safe while enjoying the types of activities you love.
Where does the concern about overheating during pregnancy come from?
Once the body becomes pregnant, keeping the developing fetus safe and on track is of utmost importance. And as for the body temperature of the fetus, preventing it from rising much higher than baseline is critical, especially in the first trimester. This is because during this period the development of key organs takes place and these processes can be adversely affected by high peaks in body temperature.
It is important to understand that the body temperature of the fetus depends on maternal body temperature. The basic research done on this topic (since the 1960s) was performed on animals. This research showed that when the mother’s body temperature is too high (above 102° Fahrenheit), it can lead to birth defects, especially during the early part of the first trimester when critical brain and organ development occurs (Edwards, 1967 ). Here are the guidelines for limiting heat exposure during pregnancy.
The fascinating ways the pregnant body dissipates heat
While the research findings above may sound alarming, fear not, because the pregnancy body naturally adjusts to allow for greater heat dissipation. Specifically, the following changes occur:
- Sweating begins at a lower body temperature. You start sweating earlier to cool off.
- More heat is lost through respiration. Breathing rate increases by 50% during pregnancy (ACE, 2011).
- There is increased heat transfer from skin to environment. Due to increased blood flow during pregnancy.
So even though the exercise does increase the body temperature, the natural adaptations of the pregnant body help to protect against any possible danger to the fetus. That said, it’s still important to follow the safety guidelines below to ensure you don’t do anything to hinder your body’s ability to dissipate heat.
What the new research shows
Very recent research, from 2019, looked at body temperature in humans, and determined that People can exercise safely in warmer conditions than we thought.
Specifically, he said that pregnant women can exercise safely for up to 35 minutes at 80 to 90% maximum heart rate at 77° at 45% relative humidity (Ravenelli et. al, 2019). Additionally, water exercise and sauna time are considered safe as long as certain safety guidelines (described below) are followed.
Guidelines for safe heat exposure during pregnancy
While the body of pregnancy naturally adapts to allow for greater heat dissipation, it is important to avoid those conditions that could make heat dissipation more difficult. Therefore, it is recommended to avoid the following (Ravenelli et. al, 2019):
- Prolonged (>35 minutes), high-intensity exercise in heat above 77° F and 45% relative humidity
- Immersion in water (>92° F) for more than 45 minutes
- Saunas (>20 minutes) above 158° F and 15% relative humidity
- Hot tubs/baths (>104° F) for more than 20 minutes
- Hot yoga
In addition to avoiding the above activities, here are some additional tips to minimize the risk of overheating:
- They drink water! Hydration is essential for So Many reasons during pregnancy, including the ability to continue sweating
- Wear clothing that allows sweat to evaporate
- If you exercise outside, do it during the cooler hours of the day (avoid 10am-4pm)
If you follow the above guidelines and have no other pre-existing conditions, rest assured that you can exercise in warmer conditions and still have a safe and healthy pregnancy.
Want additional resources?
For additional resources to help you exercise safely and Efficiently during pregnancy, explore us educational programs and services. You’ll find a variety of offerings tailored to different needs — from training, to self-directed programs, to the ability to work with an experienced coach.
Or, if you are a health and fitness professional interested in coaching pre and postnatal clients check it out ProNatal Training & Certification.
Sources:
American Council on Exercise. (2011). ACE Group Fitness Instructor Manual: A Guide for Fitness Professionals. San Diego, Print.
Edwards. MJ (1967). Congenital malformations in guinea pigs. After induced hyperthermia during pregnancy. Arch Pathol., 84(1):42-8.
Ravanelli, N., Casasola, W., English, T., Edwards, KM, Jay, O. (2019). Heat stress and fetal risk. Environmental thresholds for exercise and passive heat stress during pregnancy: a systematic review with best evidence synthesis. British Journal of Sports Medicine53(13), 799-805.
