A sauna is an enclosed room that uses dry heat to induce sweating for relaxation. High temperatures, often exceeding 150°F, can significantly elevate the body’s internal temperature. Medical professionals advise caution regarding all high-heat environments during pregnancy because the body’s ability to regulate heat is altered. The primary concern is the rapid increase in the mother’s core body temperature, which may introduce risks to the developing fetus, particularly during early gestation.
Understanding Core Body Temperature Risks
The main danger of using a sauna while pregnant is maternal hyperthermia, an elevation of the core body temperature above a safe threshold. Research indicates that a sustained core temperature of 101°F (38.3°C) or higher raises concerns for fetal development. Exposing the body to intense heat can quickly overwhelm the body’s natural cooling mechanisms, potentially leading to a dangerous temperature spike.
This rapid temperature increase is especially risky early in pregnancy when major organ systems are forming. Maternal hyperthermia during the first trimester is associated with an increased risk for neural tube defects (NTDs). The neural tube, which forms the brain and spinal cord, closes within the first month of pregnancy, often before a person is aware they are pregnant. Studies show that exposure to high heat can nearly double the risk of NTDs.
Overheating can also cause immediate complications for the mother. High heat intensifies the natural increase in blood volume and heart rate during pregnancy, leading to dehydration. Dehydration, combined with heat-induced vasodilation, increases the chance of feeling dizzy or faint.
Safety Guidelines Across Trimesters
The first trimester is considered the most vulnerable time, and medical guidance advises complete avoidance of saunas during this period. The developing fetus is most susceptible to heat-related harm during this early window of rapid cell differentiation and organ formation. Since many people do not know they are pregnant for several weeks, it is safer to err on the side of caution with heat exposure.
After the first trimester, the risk of structural birth defects decreases, but caution remains necessary due to the risk of maternal dizziness and dehydration. If a pregnant individual has medical clearance and chooses to use a sauna in the second or third trimesters, strict limitations are advised. The duration of exposure should be limited to no more than 15 minutes.
Any sauna session requires a focus on quick exit and self-monitoring. Get out immediately if any symptoms of overheating occur, such as feeling dizzy, nauseous, or experiencing a rapid heartbeat. Staying well-hydrated before and after the session is necessary to counteract fluid loss. Sitting on a lower bench, where temperatures are cooler, can also help mitigate the thermal impact.
Hot Tubs Steam Rooms and Safer Alternatives
The risk of hyperthermia applies not only to saunas but also to other high-heat environments like hot tubs and steam rooms, though the mechanism of heat absorption differs. A traditional sauna uses dry heat, which allows sweat to evaporate more easily, providing a slight cooling effect. Conversely, steam rooms utilize humid heat, and hot tubs use wet heat, both of which prevent the body from efficiently cooling itself.
Hot tubs present a particularly high risk because the body is fully immersed in hot water, often set at a constant high temperature of 104°F. This constant heat makes it difficult for the body to shed excess warmth, and a dangerous core temperature can be reached in as little as 10 minutes. Hot tub use should be limited to a maximum of 10 minutes, and the water temperature should ideally not exceed 100°F (37°C).
For relaxation and muscle relief, several alternatives offer warmth without the hyperthermia risk. These safe alternatives include:
- Taking a warm, non-scalding bath, as the water cools over time and the heat is not sustained at dangerous levels.
- Prenatal yoga and gentle stretching to alleviate muscle tension and promote mental well-being.
- Professional prenatal massage.
- Warm compresses for specific sore areas.
- Meditation to manage stress.