Hot Tub or Sauna Use While Trying to Conceive

What does the evidence say about hot tubs and saunas while trying to conceive?

1. In a controlled study, water at 39.0°C (about 102°F) took at least 15 minutes of continuous immersion to raise core body temperature to a potentially concerning level, and researchers concluded usual hot tub use is unlikely to reach that level, though prolonged sessions may. 1
2. Several studies have reported a small increased chance of neural tube defects in babies of people who had a fever or hyperthermia before the 6th week of pregnancy, but high temperatures after that point are not expected to raise that same risk. 2
3. Hot tub or sauna use during pregnancy should be limited, and extra caution around any source of heat, including hot weather, is worth taking in the early weeks when neural tube development is most sensitive to overheating. 3
4. Extended exposure to ambient heat of 30°C (86°F) or higher in the first weeks after conception has been associated with a higher rate of certain non-critical congenital heart defects, particularly of the atrial septum, in a large population study, adding to the case for limiting heat exposure broadly around conception, not just from hot tubs specifically. 4
5. Sauna use in the same hyperthermia study didn't raise participants' core temperature to the threshold researchers were watching for, largely because people left before staying long enough, which suggests personal discomfort is a natural safety check, though it shouldn't be relied on as the only precaution. 1

What to know about hot tubs and saunas while trying to conceive

• If conception is still a few months off, there's no need to give up hot tubs or saunas altogether: the clearest risk window is the first six weeks after conception, not the general preconception period, so moderate, brief sessions now are the lower-stakes time to enjoy them.
• Once you're actively trying, the two-week wait is exactly when caution matters most: neural tube development is underway before a pregnancy test would show positive, so many providers suggest capping hot tub time to a few minutes and keeping water below about 100°F, or choosing a warm bath instead.
• After a positive test, the same six-week window guidance applies: heat exposure after that point hasn't been linked to the same neural tube risk, though it's still worth keeping soaks brief and water temperature moderate for comfort and circulation.