In 1941, the US Food and Drug Administration (FDA) approved Diethylstilbestrol (DES) as a treatment for menopausal symptoms, postpartum lactation suppression, gonorrhoeal vaginitis, and atrophic vaginitis. In 1949, scientists observed that pregnancy complications, such as premature birth and foetal death, correlated with low oestrogen levels in the urine of pregnant women. This indicated that women with a history of miscarriages could potentially be treated with an oestrogen mimic like DES to prevent those complications. Consequently, physicians globally prescribed DES to millions of individuals.

However, the use of DES quickly became problematic. A 1953 study conducted by researchers at the University of Chicago found that the use of DES during pregnancy did not prevent miscarriages. In 1970, researchers linked DES to the development of clear cell adenocarcinoma of the vagina in the daughters of women who ingested DES while pregnant. Throughout 1971, further studies demonstrated additional irregularities in the glands of the daughters of DES users.

Subsequently, in November 1971, the FDA banned the use of DES during pregnancy in the United States. Despite this ban, a study published that year reported DES as an effective post-coital contraceptive, leading to its off label use as an emergency contraceptive pill on many college campuses.