Is it OK to use a hot tub during early pregnancy?

Ultrasound of 12 week old embryo
By the end of your first trimester, your baby's spine is fully formed and less vulnerable to damage from the hot water in a hot tub.

Few things are more relaxing than taking a dip in a hot tub – your stress melts away as your stiff, sore muscles loosen up. But during your first trimester of pregnancy, hot tub use can be detrimental to your baby’s developing nervous system.

Many patients ask if hot tub use is safe during early pregnancy, so I want to explain when it’s OK, and when you should to avoid a hot tub altogether.

How does hot tub use affect the baby?

Fifty years ago, researchers discovered that after a substantial heat wave, Guinea pigs on an Australian farm presented higher rates of miscarriage and litters with birth defects. The researchers theorized that the heat could have caused the significant differences.

Obviously we aren’t going to do this type of study with humans. So, to determine possible dangers to developing embryos, researchers and physicians have to ask pregnant women about exposure to extreme heat.

A number of studies seem to suggest that early pregnancy exposure to extremely hot water in hot tubs – when the water temperature is 101 degrees or more – can lead to an increased risk for neural tube defects like spina bifida.

Neural tube defects occur when there are problems with the development of the embryo’s spine and central nervous system. The risk of neural tube defects for a typical pregnancy is about 1 in 1,000. Studies suggest the risk doubles to 2 in 1,000 with exposure to hot tub water.

Timing is everything

It doesn’t take long after conception for an embryo’s spine to start forming. In fact, the spine is completely formed six weeks after a woman’s last missed period.

Roughly half of all pregnancies in the United States are unplanned, so the impact on the neural tube could take place before the woman feels any signs of pregnancy.

In other words, you’d have to have had hot tub exposure during that six-week window of early pregnancy when the embryo is vulnerable for neural tube damage to occur.

If a patient comes to me worried that they recently sat in a hot tub over the weekend, but we know she’s now 12 weeks pregnant, that’s most likely out of the range of concern. I can be very reassuring to patients in that case, and that’s a really good feeling as a physician.

We do a very good job of detecting neural tube defects at UT Southwestern – we can detect more than 95 percent of cases of spina bifida. If a patient has used a hot tub during that early pregnancy window, we can use a combination of bloodwork and ultrasound to reassure them that the likelihood their baby is affected is very low.

To soak or not to soak?

Hot tub use is one of the things women need to think about if they’re trying to get pregnant. I tell my patients, “Take your folic acid and monitor your hot tub use.”

I’m not saying you have to eliminate hot tub use completely – as I mentioned before, the risk of neural tube defects for a typical pregnancy is 1 in 1,000, and that risk doubles to 2 in 1,000 if you use a hot tub during early pregnancy.

If you want to totally eliminate the increased risk, avoid the hot tub during the first trimester of pregnancy to give yourself a buffer of a few weeks. A nice, warm bath is a safe alternative if you want to relax in the water.

If you still want to enjoy the hot tub, soak for short periods of time, make sure the water temperature is below 101 degrees, and avoid the jets where the water is usually the hottest. Once you’re past the first trimester, the risk is virtually gone.

Go ahead, pamper yourself during your pregnancy! For recommendations about massage, manicures, and hair coloring during pregnancy, read this blog post from Dr. Shivani Patel.

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