Menstrual function, menstrual suppression, and the immunology of the human female reproductive tract.

Analyses of menstrual function are important to our understanding of human evolution and can help to assess the risks of menstrual suppression, a practice increasingly recommended for women. Two evolutionary issues, however, are insufficiently appreciated in these analyses: the selection pressure infections pose to the human female reproductive system, and the variety of different-and possibly conflicting-immunological functions in the healthy human female reproductive and genital tract. Part of the reason why these issues are inadequately addressed is that reproduction is not sufficiently contextualized in evolutionary and immunological accounts. I argue that expanding the immunological context for menstrual function reinvigorates Margie Profet's (1993a) hypothesis that menstruation defends against sperm-borne pathogens. This expanded context also suggests that menstruation may have more than one function. Thus, until more is known about menstruation, we should proceed cautiously with regard to menstrual suppression.