NEW YORK (Reuters Health) - In what researchers call surprise findings, a new study suggests that women who use tampons or have sex during their menstrual periods could be less likely to develop endometriosis.

The study of women with and without endometriosis found that those who exclusively used tampons were less likely to have the condition. The results were similar for women who were at least sometimes sexually active during their periods.

However, the findings only establish a relationship between these behaviors and lower risk of endometriosis, rather than proof that they can prevent the disorder.

"It's reasonable to say...(the findings) open the door to future studies," said Dr. Harvey J. Kliman of Yale University in New Haven, Connecticut.

Kliman, the senior author on the study, told Reuters Health that his team's findings were "very surprising," given what researchers believe about the development of endometriosis.

Endometriosis occurs when the tissue that lines the uterus (the endometrium) exists outside the uterus--often in the ovaries and fallopian tubes, and almost always staying within the pelvic region. Normally, the endometrium breaks apart and is shed each month during a woman's menstrual period. But endometrial tissue outside the uterus has no outlet, and the normal surrounding may become inflamed and swollen, often leading to pain.

Experts believe that a back-flow of menstrual fluid--called retrograde menstruation--contributes to endometriosis. So anything that might enhance retrograde flow, including tampons and sex, could conceivably raise the risk of endometriosis.

Going into this new study, Kliman said, "we were absolutely convinced that sex during menstruation would be a bad thing."

But in their survey of more than 2,000 women, the researchers found the opposite pattern. When asked about their sexual activity history, women with endometriosis were less likely to say they "sometimes" or "often" engaged in sexual activity during menstruation, compared with women without the condition. They were more likely to have "never" or "rarely" done so, according to findings published in the June issue of Gynecologic and Obstetrical Investigation.

The same pattern emerged when women were asked specifically about sexual activity leading to orgasm. The authors suggest that it is possible that orgasm during menstruation might protect against endometriosis by enhancing the uterine contractions that expel menstrual fluid.

As for tampon use, fewer women with endometriosis reported exclusively using tampons currently and in the past--less than 12%, compared with 21% among healthy women. Women who used only pads had a more than twofold increase in endometriosis risk, the report indicates.

This suggestion of a protective effect of tampons "really blew our minds," Kliman said. He noted, as an explanation for the link, that tampons may help draw out "debris" during menstruation, as opposed to hindering its exit.

However, whether tampons truly ward off endometriosis is unclear. For one, this study relied on women's recall of their menstrual and sexual history. And because endometriosis symptoms include painful menstruation and sex, women with the condition may be likely to avoid sex during their periods--although, Kliman pointed out, the study asked women about their practices throughout their reproductive years.

Regardless of whether there is a protective effect, Kliman said, the findings should help "get rid of the fear" that tampons contribute to endometriosis. He noted that some have speculated that tampons--which until the mid-1980s contained dioxin--might promote endometriosis.

"This (study) makes me think that tampons certainly don't promote endometriosis," Kliman said. "I think I can say that with certainty."

SOURCE: Gynecological and Obstetrical Investigation 2002 June.

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