Episode 222 - How to get hot safely in pregnancy
[0:00] Welcome to the Great Birth Rebellion podcast. I'm your host, Dr. Melanie Jackson. I'm a clinical and research midwife with my PhD, and each episode I cast a critical eye over current maternity care practice by grappling with research and historical knowledge to help you get the best out of your pregnancy, birth, and postpartum journey.
[0:24] Hello, and welcome to today's episode of the Great Birth Rebellion podcast. I'm your host Dr Melanie Jackson and for those of you who have been here from the beginning you'll know that every single Great Birth Rebellion podcast episode is provided to you completely for free that's over like 200 antenatal and birth classes all in one, This means that this podcast relies on a few generous sponsors and the commitment that women and midwives make to purchasing my other products. This is what keeps me going and it's what keeps me making sure that I can make this podcast for you for free and to continue to provide educational resources. And this week, some beautiful listeners who are grateful for the podcast and want to keep me going contributed financially to this work. I want to thank Sarah Buckley, Jess from Victoria, Emma, Megan, Tracy from Kimberley Maternity, Steph, Karis, Jenna, Sarah from Birthworks, Brianne, Jem, Maddie, Vivian from New Zealand, Hannah, Stephanie, Natalie, Ashley, Miriam, Bianca, Emma, Brooke from Sisterbirth, and Sarah from the UK.
[1:38] Listeners, today, these women paid for you to hear this podcast episode, and to them, I am so grateful for providing such tangible support and for all of you out there listening, everything that we're doing together is making a difference for women. If you would like to send me a big thank you in the form of a financial contribution, you can give me a tip or if you want to get something a little bit more for your money, you can purchase the Guide to Giving Birth Without Pain medication. However you contribute, your dollars will go towards the Great Birth Rebellion podcast so I can keep making it. And now a huge shout out to Poppy Child from Pop That Mama, who has been a major sponsor for nearly a year now. Poppy believes in this podcast so much that she has invested a lot of dollars to make sure that it keeps going. She is an absolute queen. She's pretty much paid for your antenatal education.
[2:37] The other thing that Poppy is, is a hypnobirthing practitioner and the creator of the birth box, which is a hypnobirthing online resource to help you get ready for birth. Because hypnobirthing is a technique, It's best to get the birth box during your second or third trimester so you have a chance to practice and put into place the habit of the hypnobirthing techniques and put the oxytocin bubble tracks on repeat. This means that when you are mid-contraction, your body and mind know exactly what to do and will automatically sink into the hypnobirthing techniques so you can stay focused. You can get the birth box in the link below in the show notes and Poppy is giving
[3:20] Great Birth Rebellion listeners a unique discount code. So click on the show notes below. All right, let's get into today's episode, which is all about advice on using heat in the form of baths, heat packs, saunas during pregnancy, and we'll also talk about getting hot during intense exercise and what to do if you get a fever during pregnancy. So this episode is about getting your pregnant body hot, about the safety, risks, and how to make sure you're doing it properly.
[3:54] So if you ask the internet or AI or even your care provider about the use of heat during pregnancy, it will be so cautious as to tell you to not even take a bath while pregnant, particularly if you are a woman in the West and you're taking mainstream advice off the internet. This is what you'll read. This is certainly what you may have heard from your care provider. No hot baths in pregnancy. And they'll also tell you for sure to avoid disorder and avoid intense exercise in pregnancy to prevent overheating. But I'm here to tell you that if you were to consult the actual research about heat during pregnancy, it does not resemble the advice given to you or the current guidelines. So today I'm going to talk you through the research on heat during pregnancy, give some guidance on the safe use of heat during pregnancy with reference to some of the research. And practices from countries who have sauna as part of their culture, where maternity care providers encourage the ongoing use of sauna during pregnancy. So if it's okay for the Finnish women, surely we are not in more danger. So if you're from Finland or Sweden, or if you're in a country that regularly uses sauna, you might be very surprised by this podcast episode because you'll know that the majority of pregnant women in your country continue to sauna all the way through pregnancy. And that's what we're going to talk about.
[5:22] So first I'll cover the current mainstream Australian guidance on the use of hot baths and heat in pregnancy and then I'll go through some of the research and make reference to the Swedish and Finnish recommendations and practices to demonstrate that where you live makes a difference to the advice that you'll receive. So with all of that you might get enough information to decide how and if you want to use heat during pregnancy. I will also explain when the heat is too hot and how to know if it's gone too far so you can manage the risks of getting too hot. Because the truth is that hyperthermia in pregnancy as well as when you're not pregnant can be a danger to our bodies and the bodies of our babies. So we do want to prevent hyperthermia but that does not mean avoiding activities that make you feel hot. So I'll explain also the problem with fever during pregnancy and how not to overheat during strenuous exercise.
[6:22] All right, let's go. So it is true, as I said, that most care providers will tell you to be cautious, so cautious that you should avoid hot baths and getting hot at all during pregnancy, which usually rules out soreness. But today I'm going to explain why these recommendations are ridiculously overcautious. And instead of telling you not to do it, I'll explain how you can have hot baths, use heat packs, take saunas and exercise at high intensity and know confidently that your baby will be fine. As always I'll be citing evidence and that is all provided to you in the resource folder so you can click the link in the show notes to get access to the podcast resource folder for this.
[7:06] So this idea, not to have hot baths and saunas, came initially from some animal studies that were done on rats and guinea pigs in the late 60s. And this showed that if the animal mama's core temperature rose over 40 degrees Celsius, that this created a risk for defects in their offspring, particularly for their nervous system, which is the brain and spinal cord. And that seems to be a similar concern for humans. But if you are not a guinea pig, for humans, the proposed limit for a core temperature during pregnancy is anything that is above 38.9 degrees Celsius or 102 Fahrenheit. So above 38.9 is considered high enough to put your baby at risk of brain or spinal cord defects. Again, it's at risk. They will not definitely get a defect if your core temperature rises above 38.9 degrees Celsius or 102 Fahrenheit. It just creates a circumstance where there's an increased risk that this would happen, particularly during the time where the brain and spinal cord is forming and when it's at its most sensitive. And this is usually in about the first four to six weeks from conception.
[8:25] And the concerns about overheating in pregnancy generally are isolated to that first trimester. Now, we have a vague idea that hypothermia, which is represented by a temperature above 38.9 or 102 Fahrenheit, can cause defects for your baby because the studies that were done on women who had prolonged or uncontrolled fever or a core body temperature of greater than 38.9 degrees for a prolonged period of time, it's not just all of a sudden and then it came into being controlled, for, a long period of time, it demonstrated that there is a barely statistically significant risk for their growing baby as it can cause defects and possible pregnancy loss, especially if it happens in the first trimester, which is when the bulk of the fetal development of the organs occurs.
[9:22] And if we're going to be even more specific than that, the main but still rare defect that is believed to be caused by high core temperature above 38.9 degrees Celsius. It's the failure of the closure of the neural tube, which is what is seen to be the cause of brain and spinal cord defects. And the formation and closure of the neural tube happens in the first 28 days or the first four weeks from conception. And many women are only just discovering that they're pregnant by this time. So if anything, it's these first few weeks, possibly before you even know that you're pregnant. These are the delicate early development stages. These are the times where the neural tube is closing around that 28 day mark. And so this first trimester is where hyperthermia becomes more of a problem, particularly in those first weeks. Now, because of this, the Australian, American and UK obstetric guidelines recommend that women avoid hot things so that you can avoid the chance of hypothermia, or heat stress completely.
[10:36] But today I'm going to show you the research that specifically showed that it is incredibly hard to raise your body temperature, to 38.9 degrees in a hot bath or a sauna all by exercising and even harder to do it without noticing. The main reason why your temperature would rise that high is because of a fever and not because of your behaviors. So this is a really, I believe this is an overreaction to say don't get in hot baths, don't get in saunas, don't do things that are going to make you feel hot. Because the assumption is, is that if you feel hot, your core temperature is going to rise. But that is not true. The connection is too far to be saying to women, don't have hot baths. So a normal core body temperature is within 36.5 to 37.5 degrees Celsius or 97.7 to 99.5 Fahrenheit.
[11:35] And your body has got a very sensitive internal thermoregulation and alert system that sets off alarms in your body if you're getting too hot or too cold.
[11:48] And your body starts to alert you because we exist in a very delicate temperature balance. Our core temperature has to stay within a healthy range. Otherwise, our body can't function properly either. And our body knows that. And so it has some very sensitive and internal thermoregulation systems, alert systems, that will tell you when you are getting too hot or too cold. We do this in normal circumstances. If you're sitting in a hot car and you start to feel hot, you immediately start to notice and you take actions to reduce your temperature and to cool yourself down because your body's telling you, we are going to get too hot if this continues. You. So we're very capable of maintaining thermoregulation because our body requires specific temperature range to function healthily. If it goes out of range, your body lets you know. So the first thing I want to share is that you will not accidentally get too hot in pregnancy because your body will feel it and it will be screaming at you to cool down. So some of you out there thinking, oh my gosh, I did get in a hot bath. I did have a sauna. What's going to happen? If you felt comfortable in that hot bath or in that sauna or during that intense exercise and you didn't feel like you were overheating your core temperature did not get out of a healthy range so you can relax about that.
[13:12] So if you ask me, based on the research that I'm about to share, the recommendation to avoid hot baths, saunas, and intense exercise is a huge overreaction to the unlikely circumstance that a bath or sauna would cause your core temperature to rise to dangerous levels and stay there long enough to cause damage in your baby before you actually notice. I'm going to suggest that it's virtually impossible. So let's have a look at some of this research. And again I am grateful to researchers who perform high quality systematic reviews on subjects because they do all the heavy lifting with regards to collecting the available data and offering a great scientific summary of what it all set, so this one you can read it in full it's available in full text online again it's in the resource folder for the podcast and you can get access to it in the show notes it's called heat stress and fetal risk environmental limits for exercise and passive heat stress during pregnancy. It's a systematic review with best evidence synthesis and was published in 2018 by the British Journal of Sports Medicine. It's a high-quality peer-reviewed journal and a trusted academic publication, and it's the main paper that I'll be drawing from today.
[14:31] So what we do currently know from older studies done in the 70s is that pregnancy is a time where a rising core temperature above 39 degrees or 38.9 degrees Celsius or 102 Fahrenheit, it can create a danger or a risk to your developing baby. It doesn't mean it's definitely going to happen. So if you did get a fever that was high or you do feel like you had a heat stress or overheating event in your first trimester, that doesn't mean your baby is definitely going to have a defect. What it's saying is it's a risk factor. It increases the chance that there may have been an impact on the development of your baby in that moment. And the link between heat stress and fetal defects has not been definitely confirmed, but there appears to be a possibility that it could cause us, especially in the first trimester, as I've already said.
[15:23] And high body temperatures can occur, for example, if you have a virus that causes a fever, if you live in a very hot location and you can't cool down, if you're in a very hot bath or sauna for an extended period of time and you don't get out when your body tells you to, it can happen as a result of dehydration and heat stroke and particularly during intense and prolonged exercise if hydration is not managed. So I will stress though that in all of these circumstances, if you are in any of those circumstances and your core temperature is rising above a healthy level, you would feel incredibly uncomfortable and be completely aware that your body temperature is rising and there would be a natural instinct to cool yourself down. So for this reason, during pregnancy, it's important to be aware of circumstances is that could give you a high internal body temperature, which is the ones I've just listed, but also that hot bars and saunas or exercise cannot raise your core body temperature to dangerous levels without you noticing. So it's too far a leap for maternity care providers to connect heat inducing or hot activities, with a direct correlation to an increased core body temperature especially when there's research to show the contrary because the truth is as I said if your core temperature rises.
[16:50] To 38.9 or 39 degrees celsius or 102 fahrenheit or higher you would feel absolutely horrible just like when you have a fever when you're sick you feel absolutely horrible you know that something's not right, now there was a study performed in the 80s where they put pregnant women in hot baths and saunas and they put thermometers in their vaginas as a way of recording their core temperature So again, core temperature, we're not talking about feeling hot on the outside of your skin and on your face and your eyeballs when you're in the sauna. It's not about the external heat because your baby is inside deep in your body and your internal core temperature generally maintains itself between 36.5 and 37.5 degrees Celsius. This is the healthy range, internal body core temperature range. So even if you feel hot on the outside, it doesn't necessarily mean that your core temperature mimics what's happening on your outside skin temperature. So this is why they put thermometers in women's vaginas because it was about measuring their core temperature, not their external temperature.
[18:01] And they advised the women to stay in as long as they felt comfortable. So all women got in the bath and in the sauna. And then when they felt uncomfortable, they got out. And what they discovered when they checked the thermometers from the vaginal thermometers is that all of the women got out of the hot bath or the sauna due to discomfort before their body temperature raised to a dangerous level. None of them, none of the women in this study reached anything near a core temperature above 38.9. We actually have survival mechanisms and thermoregulation messaging that tells our body when we're getting too hot or too cold. We become uncomfortable and agitated and we will naturally seek to cool ourselves down. So even if the outside of your body feels incredibly hot, doesn't mean it's impacted your core body temperature yet.
[18:52] And so what we know is that firstly, a hot bath and hot sauna can't raise your core temperature above 38.9 without you noticing. And so it's super important that if you have decided to take a super hot bath or you are going to use sauna through pregnancy to tap into how you're feeling. This is not the time to push yourself and push through and do extreme heat exposure, even if you feel horrible. If you're in a sauna and you start to feel unwell, you immediately remove yourself. It doesn't mean that your core temperature has risen too high. It could be related to your blood pressure, which as well in a nice hot bath and a nice hot sauna, your blood pressure can drop lower. And this can be potentially what the danger could be rather than the heat.
[19:40] So in the circumstance of using heat as therapy and again, locally applied heat packs, if you want to put a really hot hot water bottle on your uterus or on your back or on your ligaments because you're feeling sore through pregnancy, this is completely safe because this is about external heat a hot pack is not going to increase your core temperature and become dangerous to your baby so go ahead and make your hot packs as hot as you can tolerate if you want them warmer you don't have to tolerate lukewarm heat packs you don't have to tolerate lukewarm baths you don't have to be frightened of spas and saunas. So if you feel like you want to take a hot bath or use a heat pack or a sauna through pregnancy, the current research does not advise against using these, especially because sensible use of these has not been linked to an increase in core maternal temperature.
[20:36] So in order to understand the limits of using heat in the form of hot saunas and baths, we can turn to countries with a rich sauna culture and see what they do. Because the fact is, is that Swedish and Finnish obstetric guidelines and research papers do not discourage women from saunaring, but instead they invite women to consider their individual needs and be wise with how long they stay. So when they interviewed Finnish and Swedish women about their use of sauna during pregnancy, what they found is that at least 98% of them, the vast majority of pregnant women, continue to use sauna through pregnancy, but they noticed that their sauna habits changed. Some of them talked about using the sauna less, reducing the temperature and not staying in as long. Again, it's all about listening to your body and understanding what it's willing to tolerate during that time. And if you don't feel like using the sauna, it's completely fine not to use it or to make it cooler or to stay in less time.
[21:40] But it's fine to use it. The advice not to use it is not founded in current evidence. So the typical suggestions for pregnant women who are saunering is around 70 degrees Celsius. And again, listen to what your body is telling you. The fact is is that these countries who have sauna and ice baths as part of their regular culture and practice is that women are not excluded from this and they're not encouraged to stop by their maternity care providers so one study that again that was done in the 80s they wanted to test this hypothesis this causal relationship, that sauna that a sauna induced hypothermia which is mild so yes it can increase your core body temperature to be in a sauna somewhere in the vicinity of 0.5 degrees up to potentially 1.3 extra degrees celsius, but not to dangerous levels, they wanted to test if sauna-induced hypothermia was linked to congenital defects. So they had about 300 women in this study whose babies were born with malformations, and they matched those women with 300 other women whose babies didn't have congenital defects because they wanted to see.
[23:00] If there was a difference in their sauna use. could this have been a causal link? And what they found is that in this particular Finnish study is that 98.5% of the pregnant women had regularly visited sauna and what they found was no difference in the sauna habits were observed between the control group. And the mothers who did end up having babies with defects. So they concluded that the relatively mild temporal hypothermia caused by a sauna could not be considered hazardous for a developing baby and are unlikely to have been the cause of these particular malformations.
[23:38] So again, the main reason that women are discouraged from hot activities is the risk of hyperthermia. So getting hot is not the problem. your core temperature rising is considered the problem because of the risk of neural tube and brain and spinal defects. However the research from Finland where the majority of women engage in sauna regularly shows that even an extreme heat such as a sauna is not enough to cause these defects because your core temperature doesn't raise that high, and Finland has one of the lowest rates of newborn defects in the world, despite their incredible and frequent use of sauna. So as it stands, hot baths, saunas, hot exercise, heat packs are all completely fine to use during pregnancy so long as you pay attention to how you're feeling. You've got to stay adequately hydrated so that you don't sweat so much that you get dehydrated and that you could eventually have blood pressure issues. So if you don't feel well, cool yourself down. And of course, if your blood pressure drops in the sauna, stand carefully. I would suggest saunering with a friend just in case you start to feel faint and dehydrated.
[24:58] So at the moment, heat is not the cause. Heat-inducing activities are not the cause of defects. But the main issue to consider is when the use of hot activities does raise your core temperature if you're not paying attention and not controlling your own temperature. So most of the time.
[25:21] Heat inducing activities, you will, your core temperature will not rise high enough to cause a problem. And as you do start to warm up, you'll know. The only time where you can't necessarily control that, because all these other scenarios of hot baths, saunas, heat packs, and exercise, you have control over those.
[25:39] But let's talk about fever, because this is the time where you don't necessarily have control over how warm your body is going to get because you're actually sick.
[25:50] So at the moment with the information that we have it seems reasonable that women should try and keep their core temperature below 38.9 degrees celsius or 102 baron height in the event of a fever, there seems to be some correlation between maternal fever in the first trimester and the possibility of defects for your baby, But this is a bit tricky because then there's some conflicting information because there was a research paper that I read that suggests that fever and newborn defects might not be connected. So my conclusion after reading some of the research papers about the possible link between maternal fever, and newborn defects, particularly in the first trimester, which is when all the baby's organs are forming, and in the very early stages of your pregnancy, the first four weeks of pregnancy is when the neural tube brain and spinal column is forming really early. You may not even know you're pregnant.
[26:52] This seems to be the sensitive period. There are some papers that I read that say there's no causal link. Others say they think there is a causal link. I don't know that we have enough information to be absolutely sure. However, we do know that hyperthermia is bad for our bodies generally. So I can only assume based on the research that exists and what we already know about the body is that when your body goes out of that normal, core temperature 36.5 to 37.5 in more higher extreme fever situations, above 39 degrees this is not a healthy state to be in you can't exist there and your body doesn't thrive there and certainly if you're also forming a baby during that time that could cause damage so if you're worried about a fever during pregnancy and you want to follow the guidelines in your country regarding temperature regulation in pregnancy. The current best advice on controlling fever in pregnancy is to keep it below 38.9. And the most reliable medication that we have for that during pregnancy is paracetamol rather than non-steroidal anti-inflammatories. When you're not pregnant, you could use anti-inflammatories to control a fever if that's what you want to do. However, during pregnancy, paracetamol seems to be the thing that is the safest option during pregnancy.
[28:13] So this is a really tricky subject because you might be in a country where your health care provider has been educated to not recommend pregnant women do anything that causes them to feel hot. And this was certainly part of my education too. Only up until a few years ago did I even consider that this couldn't possibly be true. It was when a client of mine asked me about using the sauna in pregnancy and my initial instinct was like, oh no, don't do that. you're not supposed to get hot in pregnancy. I didn't say it because my first thought was wait I know that's what I was taught but I actually haven't looked into the research myself about the use of sauna in pregnancy and when I did I was incredibly surprised to see how far away the research was to what we're currently recommending to women during pregnancy. I'm sure there are a number probably hundreds and thousands of women of you listening listening out there in in the world.
[29:13] And you're avoiding hot baths because you're scared of what it will do, although you really need them because, whoa, a hot magnesium bath on your sore pregnant body might be exactly what you need. I want to tell you that it is absolutely okay and not a danger to you or your baby to sink your full body into a nice hot magnesium bath, or even without magnesium, because if you start to overheat, your body's going to tell you, and if you're sensible, you will get out of the bath. I showed you some of those earlier studies. You're not going to accidentally overheat your body. And this is the same with exercise. If you want to exercise at a high intensity and you start to feel hot, the advice is, is don't push yourself all the way to heat exhaustion and dehydration while you're pregnant, because there's a risk that your core body temperature will rise above 38.9. And this could be a potential danger to your baby, but not every time. We're calling for sensibility in the use of heat during pregnancy because there's a possible causal link between defects for your baby if your core temperature raises above 38.9.
[30:25] That's what I want to tell you about the use of heat in pregnancy. It's been this week's episode of the Great Birth Rebellion podcast and I will see you in the next episode. To get access to the resources for each podcast episode, join the mailing list at MelanieTheMidwife.com. And to support the work of this podcast, wear The Rebellion in the form of clothing and other merch at TheGreatBirthRebellion.com. Follow me, Mel, @MelanieTheMidwife on socials and the show @TheGreatBirthRebellion. All the details are in the show notes.
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