Menstruation Model.

A common concern in women's health practice is abnormal uterine bleeding. Data recently released helps to redefine "normal" menstruation.

Starting in the 1930s, all women entering the University of Minnesota kept records of their menstrual cycles while at school and after graduation. Investigators at the World Health Organization recently analyzed these records kept by 1,100 women (ages fifteen to forty-nine)--the equivalent of 6,375 years of healthy women's menstruation cycles.

Researchers eliminated all data associated with pregnancy, postpartum time, gynecologic surgery, and hormone therapy.

The length of bleeding time averaged 6.6 days at age fifteen; six days at age twenty-one; and remained constant until the age of forty-nine, when it dropped to less than four days.

The bleeding-free period was twenty-five days at age fifteen; twenty days at age forty-one; and twenty-three days at age forty-nine.

The study shows that a normal twenty-eight day cycle is not average. However, compared to today's women using oral or injectable contraceptives, the women in the study had fewer days of bleeding. Researchers also point out that the data in this study is from healthy, Midwestern students of Scandinavian descent. The results of the study may or may not apply to other nationalities.

--Contraception, February, 1997