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Sauna During Pregnancy: 20 Minutes in Studies Is No Safety Guarantee

Medical groups advise pregnant people to avoid saunas, because passive high heat can push maternal core temperature to or above the teratogenic threshold of 39.0°C (102.2°F). A limited review found that participants in the included studies stayed below that line, but its findings do not establish that sauna use is safe. Official guidance still puts avoidance first, since you cannot measure your own core temperature inside a sauna.

TL;DR:

  • The 2019 review covered monitored sessions up to 20 minutes at 70°C and 15% humidity; its highest reading, 38.9°C, does not establish safety.
  • A CDC cited meta analysis found 4% higher odds of preterm birth for each 1°C rise in heat exposure, reinforcing caution beyond sauna settings.
  • ACOG identifies the first trimester as the greatest concern; because sauna users cannot measure core temperature reliably, ask your clinician before any heat exposure.
  • Humidity, session length, body size, fitness, medications, and pregnancy stage can affect heat tolerance, so research conditions may not match your circumstances.
  • If you develop dizziness, nausea, headache, cramping, shortness of breath, or a racing heartbeat, leave immediately; seek emergency care for severe or lasting symptoms.
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Table of Contents

What research says about core temperature and heat exposure

Researchers focus on core temperature, not the number on the sauna thermometer, because the concern is how much the body itself heats up. A core temperature of 39.0°C (102.2°F) or higher has been associated with a higher risk of birth defects such as neural tube defects.

A 2019 systematic review looked at hot, dry sauna sessions of up to 20 minutes at 70°C and 15% relative humidity. In the included studies, no pregnant participant exceeded 39.0°C, and the highest individual reading was 38.9°C. That sounds reassuring, but the review itself stresses study limitations and individual variability.

The wider heat research points in a more cautious direction:

  • Heat stress in pregnancy is linked to preterm birth, low birth weight, preeclampsia, gestational diabetes and stillbirth.
  • The highest individual reading reported in the review was close to the threshold.
  • Participants in controlled studies were monitored, while a home sauna user usually is not.
  • Individual responses vary, so one person’s safe session may be another person’s overheated one.

Meta-analysis cited by the CDC found a 4% higher odds of preterm birth (OR 1.04) for each 1°C increase in heat exposure. Small increments in heat add up, which is one reason organizations stay conservative.

What ACOG and the CDC recommend

ACOG’s public guidance says it is best not to use saunas or hot tubs early in pregnancy, because some studies link long periods in these environments to birth defects. The first trimester is the period of greatest concern. ACOG also draws a line between moderate exercise, where the body regulates its own heat, and passive heat like a sauna, which raises core temperature more readily.

The CDC takes a broader approach to heat and pregnancy. Its reproductive health guidance notes that pregnancy increases vulnerability to heat stress and recommends:

  • Staying hydrated throughout the day.
  • Watching for heat-related symptoms such as headache, cramping, dizziness, nausea and shortness of breath.
  • Building a heat action plan with your care team.
  • Checking local HeatRisk forecasts before spending time outdoors.

The appropriate advice can depend on individual circumstances, so discuss heat exposure with your own provider. That is why a conversation with your own provider matters more than any general number.

How study conditions translate to real saunas

Those numbers describe a specific research setting. They are not a guarantee for every person or every sauna.

Several things change how your body handles heat:

  • Humidity: higher humidity makes it harder for sweat to cool you.
  • Duration: longer sessions give core temperature more time to climb.
  • Body size and fitness: these affect how quickly you heat up.
  • Medications: some medications impair temperature regulation, so ask your provider before any heat exposure.
  • Stage of pregnancy: the first trimester carries the greatest concern.

Stop immediately if you feel dizzy, lightheaded, nauseated, short of breath, headachy, or notice a racing heartbeat or cramping. Those are signs your body is overheating.

Pro Tip: Because home thermometers measure the air and not your core, treat any warning symptom as a signal to leave the room, not as something to push through.

Sauna air thermometer differs from core temperature

Precautions if you and your clinician decide to use a sauna

Avoidance is the most practical advice, since people cannot accurately monitor core temperature in a sauna and responses differ. If your clinician approves some heat exposure, these steps reduce risk:

  1. Talk with your clinician first, and skip the first trimester whenever possible.
  2. Check whether any medication you take affects heat tolerance.
  3. Avoid sauna use during pregnancy unless your clinician specifically advises otherwise.
  4. Have someone nearby, and set a timer before you go in.
  5. If you feel unwell, leave the heat and seek medical advice.
  6. Step out at the very first warning symptom.
  7. If you feel faint, seek medical advice promptly.
  8. Seek immediate emergency care for fainting, severe symptoms, or symptoms that persist.

Pro Tip: Our guide on what sauna temperature is comfortable at home explains how lower settings feel, which helps you plan a gentler session.

Who should avoid saunas entirely and what to ask your clinician

Whether a health condition or medication affects heat exposure depends on your circumstances. Ask your clinician whether you should avoid heat.

Bring these questions to your next appointment: Do my medications affect heat tolerance? Is any heat exposure reasonable for me at this stage? What limits do you suggest? Which symptoms should send me to urgent care? Can we write a heat action plan together?

Five questions to discuss with a clinician

Seek immediate emergency care for severe or lasting symptoms.

Gentler at-home warmth options from our collection

Different heat devices may create different experiences, but none should be assumed safe during pregnancy. Ask your clinician before using any heat device. We do not make health claims for them, and none of these products treats a medical condition. If you are pregnant, talk with your clinician before using any heat device.

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This article is general information, not a substitute for advice from a qualified doctor. Consult a qualified healthcare professional about your own circumstances before acting on anything here.

FAQ

Is it safe to use a sauna while pregnant?

Major medical organizations generally advise avoiding saunas, especially in the first trimester. ACOG’s public guidance recommends against early-pregnancy sauna use. Ask your own clinician about your situation.

Is an infrared sauna safer than a traditional sauna during pregnancy?

Infrared devices heat differently, but the concern is your core temperature, not the sauna type. Passive heat of any kind can raise it. Check with your clinician before using any heat device.

What body temperature is a concern in pregnancy?

A core temperature of 39.0°C (102.2°F) or higher is the level linked to higher birth defect risk, as ACOG describes. You cannot reliably gauge this inside a sauna, so caution is the safer route.

What should I do if I feel overheated?

Leave the heat and seek immediate emergency care if you feel severely unwell or symptoms persist. The CDC toolkit for pregnant people lists headache, cramping, dizziness, nausea and shortness of breath as warning signs. Seek immediate emergency care if symptoms persist.

Sources

This article is for general informational and educational purposes only and is not medical advice. Consult a qualified healthcare professional regarding health conditions or before making significant changes to your wellness routine.

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