Is it safe to go into a hot tub or sauna while pregnant?
Sitting in a sauna or soaking in a hot tub may seem like the perfect remedy to soothe your pregnancy aches and pains, but both activities are risky. First of all, pregnant women are at a greater risk for dehydration, dizziness, and lower blood pressure in general, and these symptoms may intensify in extreme heat. And anything that raises your core body temperature to over 102 degrees is potentially hazardous to your baby-to-be, especially during the early months of pregnancy when his body and brain are developing. Research also shows that exposure to high temperatures can increase your baby’s risk of spina bifida, a birth disorder that occurs when a baby’s backbone doesn't fully close as it develops during the first month of pregnancy.
You may want to skip the saunas and hot tubs completely until your doctor gives you the green light after you've delivered.