Heat, Humidity and Hot Tubs

If you haven’t already realized it, you will soon discover that heat and humidity are a lot harder on you while your pregnant.

The main way for your body to get rid of excessive heat is to dilate all the blood vessels in your skin.  As we point out in our chapter on body changes during pregnancy, your blood vessels are already almost as dilated as they can be, with as much blood as possible being shunted to your uterus and kidneys.

When you enter a hot, humid environment, therefore, what little further dilation that can occur is apt to be in your skin and lower body.  This directs more blood away from your brain.  The result is that your brain tells you to “Lie down!”—that is, you faint.

Fainting is just an inconvenience.  Of more concern is that the heat regulation systems do not work as well during pregnancy.  Thus, you are more apt to get heat stroke and heat prostration.

We advise pregnant women, therefore, to take it easy in a hot environment.  Don’t exercise too much.  Drink lots of fluids.  And stay out of the sun and in air conditioning as much as possible.

At the other end of the spectrum are those who go to ski lodges in the winter and want to relax in the hot tub or sauna.

There was a study several years ago that seemed to show that exposure to high temperatures early in pregnancy increased the risk of having a baby with spina bifida.  Some animal studies added fuel to the fire.  Subsequent studies have shown that this event is really unlikely if the pregnant woman is taking adequate doses of folic acid (such as in prescription strength prenatal vitamins.)

Because of the risk of fainting, however, and the fact that exposure to a hot tub or sauna during pregnancy is apt to be just plain uncomfortable, we usually advise other means of relaxing.