You may have heard that you should not use a hot tub while you're pregnant. But why is this, and is a hot bath or a jacuzzi a safer option?
The reason behind the recommendation against hot tubs has to do with body temperature. Researchers have found that having an elevated body temperature in early pregnancy increases the risk of neural tube defects; the same finding applies to fevers during pregnancy. There's some evidence that using hot tubs in early pregnancy could increase the risk of miscarriage in addition to neural tube defects, but the evidence of the link isn't conclusive -- the more likely risk is that the baby will have health problems.
Because of the known link with neural tube defects, doctors recommend that women avoid raising their core body temperatures above 101 degrees Fahrenheit during pregnancy, not only avoiding hot tubs but also monitoring any fevers also in order to prevent them from reaching that level. Just 10 to 20 minutes in a hot tub can achieve a body temperature of 102 degrees. Thus, the best bet is to not use a hot tub during pregnancy, just to be on the safe side.
A hot bath might be a safer option if you just can't go without a hot soak. In a bath, the water cools quickly whereas a hot tub maintains a hot temperature. In addition, your body is not fully submerged in a standard bath tub, thus your temperature would rise more slowly. But even a hot bath could pose risks if the water is too hot for too long, so if you do take a hot bath, monitor your body temperature and the temperature of the water in order to avoid risk.
Sources
American Pregnancy Association, "Hot Tubs during Pregnancy." Mar 2007. Accessed 31 Aug 2008.
Li, De-Kun, Teresa Janevic, Roxana Odouli, and Liyan Liu, "Hot Tube Use during Pregnancy and the Risk of Miscarriage." American Journal of Epidemiology 2003. Accessed 31 Aug 2008.
