DAN Medical Frequently Asked Questions

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Menstruation During Diving Activities

I'm just getting into diving and have a few concerns about menstruation. Will it make me more susceptible to decompression illness? Will it put me in danger of a shark bite?

Menstruation is the cyclic, physiologic discharge through the vagina of blood and mucosal tissues from the non-pregnant uterus. The cycle is controlled hormonally and usually occurs at approximately four-week intervals. Symptoms may include pain, fluid retention, abdominal cramping and backache.

Fitness and Diving Issues

Are women at greater risk of experiencing decompression illness (DCI) while menstruating? Theoretically, it is possible that, because of fluid retention and tissue swelling, women are less able to get rid of dissolved nitrogen. This is, however, not definitively proven.
One recent retrospective review of women divers (956 divers) with DCI found 38 percent were menstruating at the time of their injury. Additionally, 85 percent of those taking oral contraceptives were menstruating at the time of the accident. This suggests, but does not prove, that women taking oral contraceptives are at increased risk of decompression illness during menstruation. Therefore, it may be advisable for menstruating women to dive more conservatively, particularly if they are taking oral contraceptives. This could involve making fewer dives, shorter and shallower dives and making longer safety stops. Four other studies have provided evidence that women are at higher risk of DCI, and in one study of altitude bends, menses also appeared to be a risk factor for bends.
Are women at an increased risk of shark attacks during menstruation? There are few reported shark attacks on women, and there are no data to support the belief that menstruating females are at an increased risk for shark attacks. The average blood lost during menstruation is small and occurs over several days. Also, it is known that many shark species are not attracted to the blood and other debris found in menstrual flow.
In general, diving while menstruating does not seem to be a problem as long as normal, vigorous exercise does not increase the menstrual symptoms. As long as the menstrual cycle poses no other symptoms or discomforts that affect her health, there is no reason that a menstruating female should not dive. However, based upon available data, it may be prudent for women taking oral contraceptives, particularly if they are menstruating, to reduce their dive exposure (depth, bottom time or number of dives per day).