Is hot tubs and male fertility safe during pregnancy?

What does the evidence say about hot tubs and male fertility during pregnancy?

1. A preconception cohort study of over 3,000 couples found hot tub or bath use three or more times a month was linked to a small, not statistically significant, reduction in monthly conception chances, with a stronger pattern in men 30 and older who had several combined heat exposures. 1
2. In an experimental study, men who sat in a 43 degrees Celsius water bath for 30 minutes at a time, repeated over one to two weeks, saw sperm concentration drop to as low as 15 to 29 percent of their starting value, with full recovery to baseline taking 14 to 16 weeks. 2
3. In workers with several hours of daily occupational heat exposure, average scrotal temperature ran about 1 degree Celsius higher than in unexposed workers, and their average sperm count was less than half that of the unexposed group. 3
4. A review of controllable lifestyle factors before fertility care describes wet heat exposure as a potentially reversible cause of low semen quality, noting that cooling the scrotum was effective at improving semen quality afterward. 4
5. The same preconception cohort study also tracked saunas, heated car seats, and tight-fitting underwear as combined heat sources, since researchers think sperm-quality effects add up across whichever heat exposures a person has in daily life. 1

Is hot tubs and male fertility safe in each trimester?

• First trimester. In the early stages of trying to conceive, occasional hot tub use is a minor factor. A large cohort study found only a weak association between hot tub or bath use and reduced monthly conception chances for most men.
• Second trimester. If you and your partner have been trying for several months without success, cutting back on hot tubs, saunas, and other regular sources of scrotal heat is a reasonable, low-cost change to make while other causes are being worked through with a provider.
• Third trimester. For couples further into a fertility evaluation, it's worth knowing that heat-related drops in sperm count and motility have been shown to fully recover, though full recovery took 14 to 16 weeks in one study, so give any change time to show up on a semen analysis.