Researchers from the University of California at Berkeley presented evidence to members of the American Association for Cancer Research this week that suggests short-term use of pregnancy-level estrogen may reduce a woman's risk of developing breast cancer. Because a full-term pregnancy at an early age greatly reduces a female's lifetime risk of the disease, researchers tested one microgram of Estradiol (an estrogenic medication sold under the brand name Estrace) each day for three weeks on rats that had never borne offspring.

According to the scientists' report, rats treated with Estradiol as well as chemical carcinogens showed no signs of mammary cancer nine months after treatment. Meanwhile, rats receiving only carcinogens had a 90 percent mammary cancer incidence. Researchers involved in the study say their inquiries should be used as a model "for developing strategies for human breast cancer prevention."