Feeling unusually hot during pregnancy is one of the most common physical complaints, and it has a straightforward explanation: your body is producing significantly more heat than usual while simultaneously undergoing hormonal shifts that raise your baseline temperature. About 35% of pregnant women report hot flashes at some point during pregnancy, and the underlying causes affect nearly everyone who’s expecting.
Progesterone Raises Your Baseline Temperature
The feeling of being overheated often starts before you even know you’re pregnant. Progesterone, the hormone that surges after ovulation and stays elevated throughout pregnancy, raises your basal body temperature by roughly 0.5 to 1 degree Fahrenheit. That might sound small, but your body is finely tuned to its resting temperature. Even half a degree sustained over weeks and months changes how warm you feel day to day, especially at night when your body would normally cool down.
This temperature shift begins in the earliest days of pregnancy and persists for the duration. It’s the same mechanism that causes some women to feel warmer in the second half of their menstrual cycle, just extended across nine months instead of two weeks.
More Blood, More Body Heat
Your blood volume increases dramatically during pregnancy, expanding by up to 50% by the third trimester. Your heart pumps harder and faster to move all that extra blood, and your blood vessels widen (a process called vasodilation) to accommodate the increased flow. This serves a critical purpose: delivering oxygen and nutrients to the placenta and your growing baby. But it also means more warm blood is flowing closer to the surface of your skin, which is why you may look flushed and feel radiantly warm even when the room is cool.
Your body actually uses this increased skin blood flow as a cooling strategy. More blood near the surface means more heat can escape through the skin. It’s your built-in radiator working overtime, and sweating increases too, particularly as pregnancy progresses. But the system doesn’t always keep up with demand, which is why you still feel hot despite your body’s best efforts.
Your Baby Is a Small Furnace
The fetus and placenta are metabolically active, meaning they generate their own heat as a byproduct of growth and development. Your baby’s core temperature runs about 0.5°C (nearly 1°F) higher than yours, and the majority of that fetal heat dissipates across the placenta into your bloodstream. A smaller amount passes through the amniotic fluid and uterine wall. Either way, all of it becomes your heat to get rid of.
As the baby grows, so does the metabolic load. Combined with the extra body mass you’re carrying (which insulates and traps heat), your body has to work progressively harder to shed that thermal energy. This is a major reason the overheating tends to get worse, not better, as pregnancy advances.
When Feeling Hot Peaks
Hot flashes and general overheating follow a predictable pattern. In a study that tracked women throughout pregnancy and postpartum, hot flashes increased steadily through pregnancy and peaked around week 30. At that point, about 24% of women reported active hot flashes at any given check-in. The timing makes sense: by 30 weeks, blood volume is near its maximum, the baby is large enough to generate substantial heat, and the extra weight makes physical cooling harder.
Some women notice the heat most at night, waking up drenched in sweat. Others feel it during physical activity or in warm environments. After delivery, hot flashes don’t disappear immediately. About 29% of women report them postpartum, peaking around week 2 after birth and gradually declining from there as hormone levels stabilize.
When Heat Becomes a Concern
Feeling warm is normal. Running a fever is different. A core body temperature above 101°F (38.3°C) in early pregnancy, particularly before the 6th week, has been linked to a small increased chance of neural tube defects. After week 6, high temperatures are not expected to carry the same risk for neural tube issues, though some studies suggest untreated fevers before week 12 may slightly raise the chance of other birth defects.
The key distinction is between the everyday warmth of pregnancy and actual hyperthermia from illness, prolonged hot tub use, or heat exhaustion. If you have a fever, treating it promptly matters more in early pregnancy than at any other time.
Practical Ways to Stay Cooler
Hydration is the single most effective tool. Your body needs significantly more fluid during pregnancy to support the increased blood volume and sweating. Experts recommend 8 to 12 cups of fluids daily (roughly 64 to 96 ounces). In the second trimester, you need about 11 extra ounces above that baseline to support additional calorie needs, and in the third trimester, about 15 extra ounces. If you’re exercising or in hot weather, you’ll need even more.
Beyond water intake, a few strategies make a real difference:
- Wear loose, breathable fabrics. Natural fibers like cotton wick moisture away from skin and allow airflow, helping your body’s natural cooling system work efficiently.
- Keep your sleeping environment cool. A fan or lower thermostat at night can offset the progesterone-driven temperature rise that disrupts sleep.
- Use cold water strategically. Running cool water over your wrists, keeping a cold washcloth on your neck, or taking a lukewarm shower can lower your skin temperature quickly.
- Avoid peak heat outdoors. Your body is already working harder to shed heat. Adding high ambient temperatures and direct sun makes the job significantly more difficult, especially in the third trimester when overheating peaks.
Night sweats can be managed by sleeping on a towel over your pillow, using moisture-wicking sheets, and keeping a glass of cold water on the nightstand. Many women find that sleeping with fewer blankets than their partner needs becomes the new normal by mid-pregnancy.