Fever During Pregnancy: Causes, Risks, and Treatment

Feeling hot during pregnancy is a very common complaint. Sometimes you experience a flush, sometimes you sweat profusely, and sometimes you can't sleep at night because your body feels hot, even though others around you feel the room is cool. For most women, this is a normal symptom of pregnancy, associated with hormonal changes, increased blood volume, and increased metabolism. [1]

It's important to distinguish subjective fever, which feels like it's "burning from the inside," from true hyperthermia, which is a real increase in core body temperature to dangerous levels. In early pregnancy, it's the mother's persistently high body temperature, rather than the usual sensation of "hot," that's associated with an increased risk of certain birth defects, particularly neural tube defects. [2]

A feeling of heat can be both physiological and a sign of problems: overheating in a sauna or hot bath, a severe viral infection with fever, an exacerbation of thyroid disease, anemia, or dehydration. Therefore, a pregnant woman's task is not to "tough it out," but to learn to listen to her body, assess accompanying symptoms, and seek help promptly if the fever is accompanied by alarming signs. [3]

Current guidelines emphasize that moderate fever, hot flashes, increased sweating, and a tendency to "overheat" are a normal part of pregnancy for a significant proportion of women. Fever becomes dangerous when the core temperature can be measured and approaches 39°C or higher, as well as when the fever is combined with fainting, severe shortness of breath, cramping abdominal pain, or signs of infection. [4]

This article discusses why pregnant women experience fever more often, what the dangers are, how to distinguish physiological hot flashes from overheating and hyperthermia, how to get properly examined, and what measures can actually help reduce a fever without harming the baby. This article is for informational purposes only and does not replace an in-person consultation with a specialist. [5]

Table 1. Heat during pregnancy: what could be behind the feeling of “very hot”

State variant	What does a woman feel?	What does this usually mean?
Hot flashes, heat in the face and upper body	A sudden wave of heat, sweat, then chills	Hormonal changes, increased blood flow to the skin
It's constantly hot, but the temperature is normal.	Feeling overheated, sweating, but no fever	Physiology of pregnancy, stress on the cardiovascular system
Heat plus high temperature on the thermometer	Fever, chills, readings above 38°C	Fever due to infection or other illness
Heat in a hot room after a sauna	Rapid increase in heat, dizziness	External overheating, risk of hyperthermia
Fever plus palpitations, trembling, weight loss	Constant heat, sweating, anxiety	Possible thyroid disease

Why do you feel hot during pregnancy: How your thermoregulation changes

During pregnancy, the body works "for two." The basal metabolic rate increases: the body expends more energy, even at rest, to provide the fetus with oxygen and nutrients. Any energy conversion in the body is accompanied by heat production, so the basal level of heat production in a pregnant woman is higher than before conception. [6]

The hormone progesterone, whose levels rise in the first weeks of pregnancy, slightly increases basal body temperature and influences the thermoregulatory center in the brain. A woman may have normal armpit readings but subjectively experience hot flashes, sudden waves of heat accompanied by flushing of the face, neck, and upper body. Similar mechanisms are known to occur in women during perimenopause, but in pregnancy, they are associated specifically with gestational hormonal changes. [7]

Increased blood volume and increased blood flow to the skin also contribute to the sensation of heat. More warm blood flows to the skin, and cutaneous vessels dilate to more easily release heat into the environment. As a result, a woman may constantly feel "hotter than everyone else," especially in closed, stuffy rooms, on public transportation, or with the slightest physical exertion. [8]

Weight also plays a significant role. As the fetus grows, body mass increases, thermal insulation changes, and heat dissipation through subcutaneous fat and clothing becomes more difficult. Furthermore, by the end of pregnancy, the cardiovascular and respiratory systems become more active, and even ordinary household activities (climbing stairs, walking in the heat) are experienced as "overheating." [9]

Finally, pregnant women experience hot flashes more often at night. This is due to a combination of hormonal fluctuations, the functioning of the thermoregulatory system during sleep, and environmental factors such as a warm blanket, a warm partner nearby, and insufficient ventilation. Nighttime hot flashes, accompanied by awakenings and sweating at a normal body temperature, are usually not dangerous, but can significantly impair sleep quality and well-being. [10]

Table 2. The main physiological factors that increase the sensation of heat

Factor	What's happening	How does it feel?
Increased metabolism	More heat is released when the body is working	A slight but constant "background" fever
Hormonal changes	Shift in the thermoregulatory center	Hot flashes, sudden waves of heat
Increase in blood volume	More warm blood flows to the skin	Constant feeling of warmth, redness of the skin
Weight gain	It's harder to dissipate heat	Intolerance to heat and stuffiness
Sleep characteristics	Warm blanket, insufficient ventilation	Night sweats, sweating during sleep

What is normal and when does fever become dangerous?

A feeling of being "hot" or "hot all the time," with a normal or slightly elevated body temperature of approximately 37.5°C, is normal for most pregnant women. This is unpleasant, but does not pose an independent threat to the fetus unless the woman is overheated externally and there is no concomitant infection or other serious condition. [11]

Danger arises when core temperature can be measured and is significantly elevated. Research shows that a sustained increase in maternal core temperature to values of approximately 39.0°C or higher in early pregnancy, especially before the sixth week, is associated with an increased risk of neural tube defects and certain other birth defects. This is true hyperthermia, not subjective hot flashes. [12]

Hyperthermia can be caused by prolonged high fevers associated with severe infections, prolonged exposure to saunas, hot tubs, jacuzzis, and other sources of intense external heat. This is the basis for the recommendations of many professional societies: avoid saunas and hot tubs during the first trimester, and subsequently avoid any procedures that cause severe overheating, dizziness, or nausea. [13]

It's important to understand that a short-term moderate increase in temperature, quickly resolved with treatment, rarely leads to serious consequences. A review of the data shows that risk is determined not only by the maximum temperature, but also by the duration of hyperthermia, accompanying hypoxia, dehydration, and the severity of the underlying disease. In most cases, when a woman seeks medical attention and receives treatment promptly, the pregnancy ends successfully. [14]

It's worth noting that overheating is also dangerous later in pregnancy. Although the risk of birth defects decreases after the sixth week, extreme heat, combined with dehydration and cardiovascular stress, can worsen maternal well-being, exacerbate chronic illnesses, cause fainting and fall injuries, and theoretically affect blood flow to the placenta. [15]

Table 3. Feeling of heat and internal temperature: guidelines for pregnant women

Situation	What does it usually mean?	What to do
Fever, sweat, but temperature up to 37.5 °C	Physiological changes	Cooling, drinking, change of clothes
Recurring hot flashes without other symptoms	Hormonal fluctuations	Observation, discussion at a scheduled appointment
Fever plus temperature 38-38.5 °C	Fever with infection	Contact your doctor soon
Fever plus temperature of about 39 °C and above	Dangerous hyperthermia, especially in the first trimester	Urgent medical attention
Heat without fever after a sauna, hot bath, or exercise in the heat	External overheating, risk of hyperthermia	Rapid cooling, drinking, monitoring your well-being

Possible causes of pathological fever and overheating

Not all fever during pregnancy is due solely to hormones. One common cause of abnormal fever is viral and bacterial infections with fever. These can include influenza, the new coronavirus, other respiratory viruses, pyelonephritis, intestinal infections, and pelvic inflammatory disease. In these cases, fever is accompanied by cough, sore throat, headache, muscle aches, lower back pain, diarrhea, and other typical symptoms. [16]

Overheating can also be caused by improper use of thermal treatments. Prolonged stays in saunas, jacuzzis, hot tubs, tanning beds, and other intense thermal treatments increase core body temperature and make it more difficult to release. Research has linked such episodes to an increased risk of neural tube defects, especially if they occur before the sixth week of pregnancy. [17]

Fever, increased sweating, increased heart rate, and a feeling of internal "warming" can be signs of thyroid dysfunction, particularly thyrotoxicosis. It is less common in pregnant women, but is sometimes first detected during this period. Thyrotoxicosis is also characterized by hand tremors, weight loss with preserved appetite, irritability, and sleep disturbances. [18]

Anemia, dehydration, and certain medications can increase the sensation of heat. With anemia, tissues are less able to receive oxygen, the heart works harder, peripheral blood flow increases, and a woman feels hot and weak even with minimal exertion. Dehydration impairs the body's ability to cool itself through sweating and circulation, so during a fever, it's important to maintain a healthy fluid intake rather than reduce it. [19]

Finally, the subjective sensation of intense heat and "hot flashes" can be intensified by anxiety, panic attacks, and stress. Emotional reactions are accompanied by the release of stress hormones, increased heart rate, and dilation of blood vessels in the skin, making hot flashes more pronounced and frightening. In such situations, it is helpful to discuss the problem not only with an obstetrician/gynecologist but also with a psychotherapist or psychologist. [20]

Table 4. Pathological fever during pregnancy: common causes

Cause	Main symptoms other than fever
Viral or bacterial infection	Cough, sore throat, body aches, fever, malaise
External overheating	Sauna, hot bath, stuffiness, dizziness
Thyrotoxicosis	Tachycardia, weight loss, tremors, irritability
Anemia and dehydration	Weakness, dizziness, pallor, dry mouth
Anxiety and panic attacks	Feeling of terror, shortness of breath, trembling, anxiety

Symptoms and Red Flags: When a Fever Requires Urgent Care

Physiological hot flashes are usually short-lived, recurring several times a day, more often at night or in stuffy rooms. They subside with cooling and are not accompanied by severe weakness, pain, or impaired consciousness. Temperature readings are either normal or slightly elevated, but do not reach a high fever. General well-being is relatively preserved between hot flashes. [21]

Warning signs include a high, persistent fever with a measured temperature of around 38°C (100.4°F) or higher, chills, body aches, severe weakness, nausea, difficulty breathing, and chest or abdominal pain. These symptoms most often indicate a severe infection or other serious conditions and require prompt medical attention. [22]

A separate type of "red flag" is the signs of overheating in a hot environment: sudden dizziness, blurred vision, dry skin with continued heat, decreased urine output, and confusion. This may indicate heat exhaustion or heatstroke, which are dangerous for both mother and fetus. In such situations, it is necessary to immediately leave the hot room, cool down, and seek emergency medical attention. [23]

A persistent fever, combined with a rapid heartbeat, tremors, weight loss, heat intolerance, and poor sleep, requires a thyroid function check. A significant number of women experience their first thyroid disease during pregnancy, so these symptoms should not be ignored. [24]

Finally, "red flags" include any episodes of fever and sweating, accompanied by cramping pain in the lower abdomen, watery vaginal discharge, bloody discharge, severe headache, and visual impairment. These may indicate impending premature labor, rupture of membranes, preeclampsia, or other obstetric complications. [25]

Table 5. Red flags for fever in pregnant women

Sign	Possible conditions	Actions
Temperature 38.5-39 °C and above	Severe infection, hyperthermia	Urgent consultation with a doctor, often hospital
Dizziness, confusion, almost no urine	Heat exhaustion or heat stroke	Call an ambulance immediately
Fever plus severe shortness of breath, chest pain	Thromboembolism, pneumonia, heart problems	Emergency medical care
Fever plus cramping pains, fluid leakage	Threat of premature birth, rupture of membranes	Urgent examination in hospital
Fever plus tachycardia, tremor, weight loss	Thyroid dysfunction	A planned, but not postponed, consultation with an endocrinologist

Diagnosis: How to distinguish subjective fever from hyperthermia

The first step is to objectively measure the sensation of heat. The doctor recommends measuring body temperature with an appropriate thermometer, if possible several times throughout the day, under the same conditions, after a short rest. Measurements in the armpit, oral cavity, and rectum will yield slightly different figures, so it's important to choose one method and stick to it. [26]

Next, a detailed medical history is collected: when the fever began, whether it is related to physical activity, being in a hot room, taking a hot bath, or visiting a sauna, and what symptoms accompany it. The patient's history is determined to include any contact with sick individuals, episodes of fever before pregnancy, and chronic diseases, including thyroid disease, cardiovascular disease, and anemia. [27]

The physical examination includes assessment of pulse and respiratory rate, blood pressure, oxygen saturation, skin examination (for redness, dryness, or sweating), and auscultation of the lungs and heart. The doctor looks for signs of dehydration, thyroid enlargement, edema, and changes in skin and mucous membrane color. An obstetric assessment of the pregnancy is also performed. [28]

Laboratory diagnostics are selected individually. If infection is suspected, a complete blood count (CBC) with leukocyte and inflammatory marker assessment, urinalysis, and, if necessary, cultures, as well as tests for influenza and other viruses, are prescribed. If thyrotoxicosis is suspected, thyroid-stimulating hormone and thyroid hormone levels are assessed. If signs of dehydration and heat exhaustion are present, electrolytes and kidney function are assessed. [29]

In complex cases where fever and overheating persist and the cause is unclear, consultation with a cardiologist, endocrinologist, or infectious disease specialist may be necessary. Doctors will jointly decide whether additional imaging tests are needed, such as a chest X-ray with fetal protection, cardiac ultrasound, or other examinations. A balance between the need for diagnosis and the safety of the unborn child is always important. [30]

Table 6. Basic diagnostic steps for fever complaints

Survey stage	Task
Temperature measurement	Distinguish between subjective fever and hyperthermia
Collection of anamnesis	Find a connection with stress, heat, and infection
Physical examination	Assess the cardiovascular and respiratory systems, signs of dehydration
Laboratory tests	Confirm or exclude infection, anemia, thyrotoxicosis
Consultations with specialists	Specify rare or combined causes

Treatment and self-care for fever during pregnancy

If the fever is due to physiological causes, non-medicinal measures are the primary approach. It is recommended to wear loose, multi-layered clothing made of natural fabrics so that layers can be easily removed or added as your condition changes. It is important to maintain a comfortable room temperature, ventilate the room frequently, and use fans or air conditioning if necessary, avoiding direct cold air flow onto the abdomen. [31]

Maintaining adequate fluid intake helps the body better regulate temperature. Insufficient fluid intake impairs sweating and circulation, increasing the risk of overheating. Most pregnant women, unless otherwise indicated, are advised to drink small amounts of water throughout the day, based on thirst and a doctor's recommendations, especially in hot weather and during active lifestyles. [32]

Simple measures can help with hot flashes and episodes of fever: washing with cool water, taking a cool shower, using wet wipes, resting in the shade or a cool room, and applying cool (not ice-cold) compresses to the neck, wrists, and armpits, where the body surface is close to large blood vessels. However, drastic contrast procedures, ice baths, or douches are not recommended, especially during pregnancy. [33]

If a fever is accompanied by a deterioration in well-being, the decision to administer antipyretics and other medications is made by a doctor. In most recommendations, the doctor selects the drug, dosage, and duration of treatment, weighing the risk of hyperthermia against the possible impact of the medication on the fetus. In infections, not only temperature control is important, but also comprehensive etiotropic treatment aimed at the underlying cause. [34]

Self-medication with traditional warming or, conversely, sharply cooling methods, unverified supplements, and medications without a doctor's prescription is unacceptable during pregnancy. This especially applies to strong antipyretics, combination cold medications, and herbs with potentially toxic or hormone-like effects. Any questions about fever medications should be discussed with an obstetrician-gynecologist or general practitioner in advance. [35]

Table 7. Dos and Don'ts for Fever During Pregnancy

Action	Safety assessment
Drink clean water, wear light clothing, ventilate the room	Recommended
Take a cool shower, use soft cooling compresses	Acceptable and useful
Taking strong antipyretic drugs on your own	Not recommended, only as prescribed by a doctor
Visit a sauna, jacuzzi, or very hot bath	Not recommended, especially in the first trimester
Use "folk" remedies of unknown composition	Not recommended, may cause toxicity and allergies

Prevention of overheating and hot conditions

Preventing overheating begins with a sensible approach to heat and exercise. Pregnant women are advised to avoid prolonged exposure to hot and stuffy rooms, direct midday sun, and intense exercise in high temperatures and humidity. If physical activity is approved by a doctor, it's best to choose morning or evening hours, shade, and cool rooms, taking breaks for rest and fluids. [36]

Layers and natural materials are preferred in clothing. Synthetics are less breathable and retain moisture, increasing the feeling of a hot "greenhouse." Loose dresses, loose pants, cotton T-shirts, and comfortable underwear help the skin "breathe" and reduce sweating. It's also important to choose comfortable shoes, especially in hot weather, to avoid increasing swelling and overheating of the feet. [37]

Pay attention to your microclimate at home. Regular ventilation, curtains or blinds to protect from direct sunlight, and, if necessary, air conditioners and fans can help maintain a comfortable temperature. When using an air conditioner, avoid directing airflow onto the abdomen and avoid creating too large a temperature difference between the outside and indoor temperatures. [38]

Maintaining a healthy weight and preventing excessive weight gain also reduces the tendency to overheat. A diet with sufficient vegetables, fruits, and protein, and limiting very fatty and highly salty foods, promotes better heat tolerance. Avoiding smoking and alcohol, which impair cardiovascular function and increase stress on the body, is especially important. [39]

Finally, good sleep and stress management reduce the severity of hot flashes. Relaxation techniques, breathing exercises, moderate daytime physical activity, and keeping the bedroom cool and dark can help reduce nighttime hot flashes and improve overall well-being. If anxiety and frequent panic attacks are severe, psychological support or psychotherapy may be worth considering. [40]

Table 8. Daily steps to prevent overheating during pregnancy

Direction	Specific recommendations
Physical activity	Walk in the morning and evening, avoid exercising in the heat
Clothing and underwear	Natural fabrics, loose fit
Microclimate at home	Ventilation, protection from direct sunlight, reasonable use of air conditioning
Nutrition and weight	Balanced diet, weight gain control
Psychological comfort	Sleep, rest, stress management techniques

Frequently Asked Questions

Is it normal to feel constantly hot during pregnancy, but the thermometer shows a normal temperature?
Yes, for many pregnant women, this is a typical physiological response. Due to hormonal changes, increased blood volume, and increased metabolism, the body produces more heat, and the skin actively releases it into the environment. If the body temperature is normal and there is no noticeable weakness, shortness of breath, or chest or abdominal pain, this is most often a normal reaction. However, it is worth discussing such sensations with your doctor at a routine appointment. [41]

What are the dangers of visiting a sauna or hot tub during pregnancy, just to "warm up"?
Prolonged exposure to high temperatures can lead to dangerously elevated core body temperature. Research links such episodes of hyperthermia in early pregnancy with an increased risk of neural tube defects and certain other birth defects. Therefore, most professional organizations recommend avoiding saunas, hot tubs, and jacuzzis, especially in the first trimester, and later, preventing overheating and feeling unwell. [42]

Is it okay to exercise if you feel hot during exercise?
Moderate physical activity during an uncomplicated pregnancy is generally beneficial and recommended. However, it's important to avoid exercising in hot and stuffy rooms, in direct sunlight, or in high humidity to prevent overheating. It's recommended to choose a comfortable temperature, take breaks to drink, and stop exercising if you experience dizziness, nausea, severe shortness of breath, or pain. Detailed exercise regimen recommendations should be discussed with an obstetrician/gynecologist. [43]

What should you do if you're constantly hot at night and can't get enough sleep?
Simple measures can help: keeping the bedroom cool, wearing lightweight bedding, cotton pajamas, a glass of water by the bed, and airing out the room before bed. When awakened by a hot flash, you can splash your face with cool water, take a few slow, deep breaths, and briefly turn on a fan if needed. If the nighttime fever is accompanied by palpitations, anxiety, fear, and panic, it's worth discussing the situation with a doctor and, if necessary, seeking psychological support. [44]

When does a fever during pregnancy require immediate medical attention?
Urgent medical attention is required if a fever is combined with a high temperature of 38.5-39°C or higher, severe shortness of breath, chest or abdominal pain, altered consciousness, inability to urinate, cramping pain and vaginal leakage, or bloody discharge. These are signs of a severe infection, heatstroke, thromboembolism, or obstetric complications that are dangerous for both mother and baby and require immediate diagnosis and treatment. [45]