Suggested limits to the use of the hot tub and sauna by pregnant women.

Because of reports of the potential risk of maternal hyperthermia to a developing embryo or fetus, studies were done to determine the length of time a woman must stay in a hot tub or sauna before her temperature reaches 38.9 degrees C. The vaginal temperatures of 20 nonpregnant women of childbearing age were recorded while they sat in hot tubs set at 39.0 degrees C or 41.1 degrees C and in a sauna with an average temperature of 81.4 degrees C. Five women were able to remain in the 39.0 degrees C tub and six in the 41.1 degrees C tub until their temperature reached 38.9 degrees C, but in none did their temperature reach that level before 15 minutes in the 39.0 degrees C tub or 10 minutes in the 41.1 degrees C tub. The remainder left in discomfort while their body temperatures were lower. This indicates that the usual use of hot tubs is unlikely to raise a woman's body temperature to potentially teratogenic levels, although prolonged use may. None of the women were able to remain in the sauna long enough for their temperature to reach 39.9 degrees C.