A hot flash during pregnancy is a sudden, intense sensation of heat spreading across the upper body, typically concentrated in the chest, neck, and face. This rush of warmth is often accompanied by flushing, sweating, and sometimes a rapid heartbeat, lasting anywhere from a few seconds to several minutes. Experiencing these vasomotor symptoms, particularly in the later stages of gestation, is common. Studies show that over one-third of expectant individuals report flashes at some point during pregnancy. This occurrence in the third trimester is a normal physiological response to the body’s adjustment process.
Why Hot Flashes Occur in Late Pregnancy
The primary driver behind third-trimester hot flashes involves dramatic fluctuations in reproductive hormones that directly impact the body’s temperature regulation center. High levels of estrogen and progesterone make the hypothalamus, the body’s internal thermostat, more sensitive to minor changes in core temperature. This hormonal shift effectively lowers the thermal comfort zone, causing the body to trigger a cooling response—the hot flash—even when the ambient temperature is comfortable.
A significant increase in basal metabolic rate (BMR) also contributes substantially to the feeling of excessive warmth. The body expends more energy to support the rapid growth of the fetus and the placenta, a process that inherently generates internal heat. This accelerated metabolism means the body is continually producing more heat than usual, making it harder to dissipate and easier to feel overheated.
The cardiovascular system undergoes massive changes, leading to a substantial increase in blood volume, often by as much as 50%. This greater volume requires the heart to pump blood with increased cardiac output. To shed the extra heat generated by the higher metabolic rate and the fetus, blood vessels near the skin’s surface widen, a process called vasodilation. This peripheral flushing brings warm blood closer to the skin to release heat, creating the sudden, noticeable sensation of a hot flash and visible redness.
When to Seek Medical Guidance
While the common hot flash is a benign symptom of pregnancy, it is important to distinguish this temporary warmth from a true fever, which requires medical attention. A hot flash is typically brief and does not cause a sustained elevation in core body temperature. A true fever, defined as a temperature of 100.4°F (38°C) or higher, is a sign of a systemic infection, such as a urinary tract infection or the flu, and should be reported to a healthcare provider.
A medical evaluation is also warranted if the hot flashes are accompanied by other signs of potential complications. This includes experiencing chills or shaking, which often signal an infection, or a severe, persistent headache that does not resolve. Sudden or excessive swelling in the hands, face, or feet, along with vision changes, may indicate a blood pressure issue like preeclampsia, which is a serious concern in the third trimester.
Additionally, symptoms such as dizziness, chest pain, or difficulty breathing in conjunction with a hot flash should prompt immediate contact with a provider. These could be signs of a condition unrelated to normal temperature regulation. Consult a medical professional if the flashes are profoundly disruptive to sleep, cause significant distress, or if there is any doubt about whether the symptom is a normal discomfort or a sign of an underlying illness.
Strategies for Managing Discomfort
Managing the discomfort involves simple, practical adjustments to clothing and environment to help the body regulate temperature more efficiently. Wearing loose-fitting clothing made from breathable, natural fibers like cotton allows air to circulate against the skin, which aids in the evaporative cooling process. Dressing in layers is also helpful, enabling quick removal of outer garments when a flash begins and allowing for immediate temperature adjustment.
Staying well-hydrated with cool water helps to replace fluids lost through sweating and assists the body’s internal cooling mechanisms. Keeping a glass of cold water nearby and sipping it frequently can help to lower the core temperature during an episode. Using a fan, whether a small handheld device or keeping the air conditioning or a ceiling fan on at night, can create an immediate, localized cooling effect.
Certain lifestyle factors can inadvertently trigger or intensify a hot flash and should be minimized or avoided during the third trimester. Stress and anxiety are known to worsen the frequency and severity of vasomotor symptoms, so practicing simple relaxation techniques, such as slow, deep breathing, can be beneficial. Common culprits to avoid include:
- Consuming spicy foods, which can increase internal body temperature.
- High amounts of caffeine.
- Very hot beverages.