DES, or diethylstilbestrol, was widely used in the United States, Europe and elsewhere from the 1940s through the 1960s to prevent miscarriage, premature birth, bleeding and other problems. Many companies made and sold it as pills, creams and other forms. Studies later showed it didn't work. The government told doctors to stop using it in pregnancy in 1971, after DES daughters in their late teens and 20s were found to be at higher risk of a rare form of vaginal cancer. Further research has tied DES to infertility and other health problems.