Diethylstilbestrol: Side Effects

The Medicines and Healthcare products Regulatory Agency (MHRA) regulates medicines supplied in the United Kingdom. Our activity spans the whole of a medicine’s lifecycle. The MHRA continuously assesses the benefit risk balance of all medicines at the time of initial licensing and throughout their use in clinical practice, carefully evaluating any emerging evidence on their benefits and risks.

Diethylstilbestrol (DES), also referred to as stilbestrol/stilboestrol, is an oestrogenic hormone formerly used in the treatment of threatened miscarriage and suppression of lactation. There are safety concerns with DES related this historical usage. Its use is now contra-indicated in pregnant women, it is not suitable for pre-menopausal women, and it should not be prescribed to children or young people due to its carcinogenic potential.

The first concern relates to women exposed to DES in utero when their mothers were pregnant and taking the drug for threatened miscarriage. Daughters of individuals exposed to DES in utero are at increased risk of clear cell cancer of the cervix and vagina.

The second concern relates to women who were exposed to DES whilst pregnant to prevent miscarriage or following pregnancy, in order to supress lactation. A potential risk of breast cancer in women who were given DES was identified in the 1980’s and confirmed in further studies in the 1990s.

The current advice from UK Health Security Agency (UKHSA) is that routine cervical screening is appropriate for those who were exposed to DES in utero. Participation in the National Breast Screening Programme is also recommended for those women exposed to DES. The UKHSA’s advice is available at the following link:

https://www.gov.uk/government/publications/cervical-screening-programme-and-colposcopy-management/5-screening-and-management-of-immunosuppressed-individuals