Postcoital Diethylstilbestrol

FDA Drug Bulletin, May 1973

IN AGREEMENT WITH ITS extragovernmental physician-advisers, FDA has approved, under restricted conditions, postcoital (contraceptive) use of diethylstilbestrol (DES), a synthetic estrogen.

Adequate evidence to support the use of any other estrogen for this purpose is not presently available.

The Agency considers the use of DES for this purpose to be safe only as an emergency measure (in situations such as rape, incest, or where, in the physician’s judgment, the patient’s physical or mental well-being is in jeopardy) and explicitly warns against its routine or frequent use as a contraceptive.

Physicians are urged, prior to prescribing DES for this purpose, to inform patients (or guardians) fully of the possible side effects of the drug, and of alternative measures available and their hazards, so that the patient may participate in an informed way in the decision to use the drug. Pregnancy should be ruled out by appropriate tests prior to instituting therapy, so that no unnecessary exposure of a fetus to DES occurs.

The efficacy of DES in preventing pregnancy depends upon the time-lapse after coitus and dosage of the drug. The currently recommended dosage is 25 mg twice a day for 5 continuous days beginning, preferably, within 24 hours and not later than 72 hours after exposure. When this dosage is given within the specified time interval after sexual intercourse, DES is highly effective in preventing conception. But the patient must be warned to take the full course of the drug in spite of the nausea which commonly occurs, if it is to be effective.

There is at present no positive evidence that the restricted postcoital use of DES carries a significant carcinogenic risk either to the mother or fetus. However, because existing data support the possibility of delayed appearance of carcinoma in females whose mothers have been given DES later in pregnancy, and because teratogenic and other adverse effects on the fetus with the very early administration recommended are ill understood, failure of postcoital treatment with DES deserves serious consideration of voluntary termination of pregnancy.

Before prescribing, the physician should be familiar with the complete FDA-approved labeling on products intended for this use.

More Information – Abstract from WikiVisually

  • In May 1973, in an attempt to restrict off-label use of DES as a postcoital contraceptive to emergency situations such as rape, a FDA Drug Bulletin was sent to all U.S. physicians and pharmacists that said the FDA had approved, under restricted conditions, postcoital contraceptive use of DES. (In February 1975, the FDA Commissioner testified that the only error in the May 1973 FDA Drug Bulletin was that the FDA had not approved postcoital contraceptive use of DES.)
  • In September 1973, the FDA published a proposed rule specifying patient labeling and special packaging requirements for any manufacturer seeking FDA approval to market DES as a postcoital contraceptive, inviting manufacturers to submit abbreviated new drug applications (ANDAs) for that indication, and notifying manufacturers that the FDA intended to order the withdrawal of DES 25 mg tablets (which were being used off-label as postcoital contraceptives).
  • In February 1975, the FDA said it had not yet approved DES as a postcoital contraceptive, but would after March 8, 1975 permit marketing of DES for that indication in emergency situations such as rape or incest if a manufacturer obtained an approved ANDA that provided patient labeling and special packaging as set out in a FDA final rule published in February 1975. To discourage off-label use of DES as a postcoital contraceptive, in February 1975 the FDA ordered DES 25 mg (and higher) tablets removed from the market and ordered the labeling of lower doses (5 mg and lower) of DES still approved for other indications be changed to state: “THIS DRUG PRODUCT SHOULD NOT BE USED AS A POSTCOITAL CONTRACEPTIVE” in block capital letters on the first line of the physician prescribing information package insert and in a prominent and conspicuous location of the container and carton label.
  • In March 1978, a FDA Drug Bulletin was sent to all U.S. physicians and pharmacists which said: “FDA has not yet given approval for any manufacturer to market DES as a postcoital contraceptive. The Agency, however, will approve this indication for emergency situations such as rape or incest if a manufacturer provides patient labeling and special packaging. To discourage ‘morning after’ use of DES without patient labeling, FDA has removed from the market the 25 mg tablets of DES, formerly used for this purpose“.


  • Selected Items, from the FDA Drug Bulletin, California Medicine, NCBI PubMed PMC1455105, May 1973.
  • Emergency contraception, DES, wikivisually.

Compounds interfering with ovum implantation and development – The role of estrogens

Though this study was not statistically significant, it represented the first time that prevention of implantation was demonstrated – with DES usage – in humans


“It has been known for many years that estrogens interfere with early pregnancy in the rabbit and other specics.”…

…”In spite of evidence that success in the macaque should be paralleled by success in man, initial human experimentation was undertaken with some trepidation.

The first cases were rape cases. All of the subjects received 50 mg. of stilbestrol for 4 to 6 days after exposure. The chance of pregnancy following rape is uncertain for many obvious reasons. Sometimes no sperm could be found in the cervix or vagina. In a few instances, temperature charts were started; if no rise occurred, no drug was given. In most of the cases accepted for treatment, exposure occurred near midcycle and fern crystallization of cervical mucus as well as presence of sperm were demonstrated. In this small series of patients, none has become pregnant so far. The subsequent menstruation was generally unremarkable, although in some instances it was either scantier or more profuse or prolonged than usual. Side effects, when they occurred, were those usually associated with administration of estrogen; they consisted of nausea and breast soreness, which ceased shortly after medication was stopped.

A limited number of courageous volunteers furnished an opportunity for further and more adequate observation. Coitus took place at midcycle near the time of the temperature rise. Fern crystallization and Huhner tests with motile sperm were obtained
in most instances.

The apparent effect of 5 to 50 mg. of stilbestrol or 0.5 mg. of ethinyl estradiol on the biphasic temperature curve chart is to counteract the thermogenic effect of progesterone or to shorten the luteal phase.

From these charts it was anticipated that the secretory changes in the endometrium might be altered. However, instead of a proliferative or hyperplastic endometrium, endometrial biopsies taken on postovulation days 5 to 7 and 10 to 12 showed a progestational effect with secretion in some instances on both sides of the nucleus, occasionally almost suggestive of an Arias-Stella reaction. The stroma was dense in some areas, markedly edematous in others. Basal vacuolization often persisted up to menstruation, sometirnes giving an early secretory appearance late in the cycle.

In these preliminary trials there have been no pregnancies. While of interest, these clinical studies are incomplete and have as yet no statistical significance.” …


  • Compounds interfering with ovum implantation and development. 3. The role of estrogens, American journal of obstetrics and gynecology, NCBI PubMed PMID: 4959099, 1966 Nov.
  • Image credit thinglink.

Association of DES use with increased B‐cell NHL risk

Pregnancy‐related factors and risk of B‐cell non‐Hodgkin lymphoma among women in Los Angeles

2018 Paper Abstracts

… “Pregnancy‐related factors evaluated included pregnancy history [ever (full‐term) pregnant, number of full‐term pregnancies], breast‐feeding (ever breast‐fed, duration, number of children breast‐fed), nausea during pregnancy that required treatment or hospitalization, diethylstilbestrol (DES) use during pregnancy and lactation suppressant use after full‐term pregnancy.” …

… “However, women who used DES during a pregnancy had two‐fold greater risk of B‐cell NHL overall than ever pregnant women who never used DES (OR = 2·37, 95% CI = 1·03–5·44). Notably, use of DES during pregnancy was associated with five‐fold greater risk of MZL (OR = 5·54, 95% CI = 1·76–17·45). This association is of potential interest as DES is known to alter immune function and is considered an oestrogenic endocrine disruptor.” …

… “In conclusion, our results provide evidence that increased parity, early age at first full‐term pregnancy, and breast‐feeding are associated with decreased risks of B‐cell NHL. These associations are also observed with breast cancer, and warrant further investigation to uncover whether similar anti‐carcinogenic mechanisms or specific hormone‐related immune alterations are responsible. Our report is the first suggesting the association of DES use with increased B‐cell NHL risk, particularly MZL, and warrants further investigation in collaborative efforts. Although no DES longer in use, should the association be replicated, it could provide important clues towards pinpointing biological mechanisms important for lymphomagenesis.” …


  • Pregnancy‐related factors and risk of B‐cell non‐Hodgkin lymphoma among women in Los Angeles, Wiley Online Library, 29 November 2018.
  • Featured image credit lymphoma-action.

Breast cancer risk for women exposed in utero and their offspring

Diethylstilbestrol: Potential health risks for women exposed in utero and their offspring

2017 Study Abstract

An increased risk of breast cancer has been well documented for women who took DES during pregnancy, and is estimated to be 30% greater than in unexposed women.

Long-term US studies of women exposed in utero reveal an increased risk of breast cancer in women age 40 years and older, with a hazard ratio of 1.82 (95% CI, 1.04-3.18) when compared with unexposed women. European follow-up studies do not support the finding of an increased breast cancer risk in women exposed to DES in utero. However, this may be due to the fact that the European cohort of women studied were 10 years younger than the American cohort and thus, at the time, included many women under age 40 years.

Animal studies suggest a transgenerational risk specifically for breast cancer in female offspring of women exposed to DES in utero, but this has not been supported by current patient data from United States or European follow-up studies.



DES ability to produce DNA adducts and breast cancer

Diallyl sulfide inhibits diethylstilbesterol-induced DNA adducts in the breast of female ACI rats

2005 Study Abstract

Diethylstilbestrol (DES) is metabolized to reactive intermediates that produce DNA adducts and ultimately cancer. Diallyl sulfide (DAS) has been shown to inhibit the metabolism of several procarcinogens.

The ability of DES to produce DNA adducts in microsomal, mitochondrial, and nuclear in vitro metabolic systems and in the breast of female ACI rats, as well as ability of DAS to inhibit DNA adducts were investigated.

Microsomes, mitochondria, and nuclei isolated from breast tissue of female ACI rats were used to catalyze oxidation reactions. Female ACI rats were treated i.p. as follows: (1) corn oil, (2) 200mg/kg DES, (3) 200mg/kg DES/200mg/kg of DAS, (4) 200mg/kg DES/400mg/kg DAS. DES produced DNA adducts in each metabolic system. The relative adduct levels were 2.1 x 10(-4), 6.2 x 10(-6), and 2.9 x 10(-7) in microsomal, mitochondrial, and nuclear reactions, respectively. DAS inhibited DNA adducts in each metabolic system. The percent inhibition ranged from 86% in microsomes to 93% in nuclei.

DES produced DNA adducts in mtDNA and nDNA. DAS completely inhibited the DES-induced mtDNA adducts and caused a dose dependent decrease in nDNA adduct formation.

These findings suggest that DAS could inhibit DES-induced breast cancer by inhibiting its metabolism.


  • Diallyl sulfide inhibits diethylstilbesterol-induced DNA adducts in the breast of female ACI rats, Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association, NCBI PubMed PMID: 15989972, 2005 Sep.
  • DNA adducts image credit

DES exposure and the aging woman: mothers and daughters

DES mothers have a 30% higher risk of breast cancer

2002 Study Abstract

Diethylstilbestrol (DES), the first orally active artificial estrogen ever developed, was prescribed to several million pregnant women during the 1940s through the 1960s in the mistaken belief that it reduced the risk of miscarriage.

In 1971, the US Food and Drug Administration contraindicated its use in pregnancy when DES was associated with the development of vaginal clear cell adenocarcinoma (CCA) in daughters exposed in utero.

In daughters whose mothers took DES during pregnancy, the drug has been associated with congenital malformations of the reproductive tract, fertility problems, a possible increased risk of cervical carcinoma in situ, and a presumed lifetime risk of vaginal and cervical CCA.

DES mothers have an increased risk of breast cancer (RR = 1.3).

DES sons have an increased prevalence of urogenital anomalies, and a possible increased risk of testicular cancer.



DES as genotoxic agent leading to breast cancer

Can estrogenic radicals, generated by lactoperoxidase, be involved in the molecular mechanism of breast carcinogenesis?

2000 Study Abstract

Mutations of regulatory genes, which perturb the mechanism of cell replication resulting in abnormal cell proliferation, are the main cause of cancer.

Many endogenous and exogenous chemicals (including estrogenic hormones) are known to represent a major carcinogenic risk for humans. 2-OH- and 4-OH-derivatives of estrogenic molecules have been shown to form stable adducts with purine DNA bases and act as ‘depurinating’ agents, thus altering gene transcription.

Lactoperoxidase (LPO), which is produced by mammary glands, is likely to be involved in breast carcinogenesis, because of its ability to interact with estrogenic hormones and oxidise them through two one-electron reaction steps.

We investigated the reactivity of LPO towards five molecules:

  • 17-beta-estradiol (a natural hormone),
  • diethylstilbestrol (a synthetic drug, supplied to pregnant women for preventing spontaneous abortion),
  • exestrol (a synthetic antigonadotropic estrogen),
  • 2-OH-
  • and 4-OH-estradiol (catabolic products of estradiol).

Enzymatically generated radical derivatives of such molecules were stabilized by spin-trapping or by chelation of a diamagnetic metal ion and characterized with EPR spectroscopy. A kinetic study of the oxidation process was carried out using EPR and UV-visible spectroscopy.


  • Can estrogenic radicals, generated by lactoperoxidase, be involved in the molecular mechanism of breast carcinogenesis?, Redox report : communications in free radical research, NCBI PubMed PMID: 10994878, 2000.
  • Image credit Grace Madeline.

Carcinogenicity of estrogens in human breast epithelial cells

image of breast epithelial cells

DES induces in HBEC phenotypic changes indicative of cell transformation, associated with significant genomic alterations

2001 Study Abstract

Epidemiological and clinical evidences indicate that breast cancer risk is associated with prolonged ovarian function that results in elevated circulating levels of steroid hormones. Principal among these is estrogen, which is associated with two important risk factors, early onset of menarche and late menopause.

However, up to now there is no direct experimental evidence that estrogens are responsible of the initiation of human breast cancer. We postulate that if estrogens are causative agents of this disease, they should elicit in human breast epithelial cells (HBEC) genomic alterations similar to those exhibited by human breast cancers, such as DNA amplification and loss of genetic material representing tumor suppressor genes. These effects could result from binding of the hormone to its nuclear receptors (ER) or from its metabolic activation to reactive metabolites.

This hypothesis was tested by treating with the natural estrogen 17beta-estradiol (E2) and the synthetic steroid diethylstilbestrol (DES) MCF-10F cells, a HBEC line that is negative for ER. Cells treated with the chemical carcinogen benzo (a) pyrene (BP) served as a positive control of cell transformation.

BP-, E2-, and DES-treated MCF-10F cells showed increases in survival efficiency and colony efficiency in agar methocel, and loss of ductulogenic capacity in collagen gel. The largest colonies were formed by BP-treated cells, becoming progressively smaller in DES- and E2-treated cells. The loss of ductulogenic capacity was maximal in BP-, and less prominent in E2- and DES-treated cells. Genomic analysis revealed that E2- and DES-treated cells exhibited loss of heterozygosity in chromosomes 3 and 11, at 3p21, 3p21-21.2, 3p21.1-14.2, and 3p14.2 14.1, and at 11q23.3 and 11q23.1-25 regions, respectively. It is noteworthy that these loci are also affected in breast lesions, such as ductal hyperplasia, carcinoma in situ, and invasive carcinoma.

Our data are the first ones to demonstrate that estrogens induce in HBEC phenotypic changes indicative of cell transformation and that those changes are associated with significant genomic alterations that might unravel new pathways in the initiation of breast cancer.


  • Carcinogenicity of estrogens in human breast epithelial cells, APMIS : acta pathologica, microbiologica, et immunologica Scandinavica, NCBI PubMed PMID: 11297193, 2001 Jan.
  • Image credit scitechdaily.

DES and breast cancer risk

Experimental study on relationship between exogenous estrogen and breast cancer risk

1997 Study Abstract

To investigate the relationship between exogenous estrogen and breast cancer risk.

Female rats were randomly divided into three groups, namely diethylstilbestrol (DES), norethindrone compositae (CoNET) and control group. The histological structure and ultrastructural changes of mammae were observed. The levels of sexual hormones in serum were determined and the AgNOR counts, DNA contents and steroid receptor contents in mammary epithelium were also detected.

In DES group, the level of progesterone (10.38 ng/ml) was obviously lower than that in the control group (13.37 ng/ml); the incidence of hyperplasia of mammary gland (73.33%) was significantly higher than that in the control group (7.69%); and the degree of hyperplasia was obviously more serious than that in the control group. Moreover, there were 13.33% of rats with atypical hyperplasia in DES group. The DNA contents, AgNOR counts and estrogen receptor (ER) positive rate were markedly higher in DES group (95.60, 2.43 and 71.71% respectively) than in the control group (83.07, 1.88 and 40% respectively). However, in CoNET group, there were no obvious influences on ER, AgNOR and DNA in mammary epithelium.

Exogenous estrogen (DES) could affect the levels of sexual hormones in serum, accelerate the DNA duplication, increase the AgNOR counts and ER contents, and induce atypical hyperplasia and ultrastructural changes of mammary gland, hence becoming a latent risk factor of breast cancer. However, the results failed to suggest that the contraceptive, CoNET, could increase the risk of breast cancer.


  • Experimental study on relationship between exogenous estrogen and breast cancer risk, Chinese medical journal, NCBI PubMed PMID: 9594309, 1997 May.

DES use during pregnancy and fatal breast cancer

Diethylstilbestrol and risk of fatal breast cancer in a prospective cohort of US women

1996 Study Abstract

The authors examined the association between the use of diethylstilbestrol during pregnancy and the risk of subsequent fatal breast cancer in a large prospective study of US adults.

After 9 years of follow-up, 1,574 cases of fatal breast cancer were observed among 501,536 gravid women who reported no prior history of cancer in 1982.

Results from Cox proportional hazards models showed a positive association between a history of diethylstilbestrol exposure (reported by 3.9% of all women) and fatal breast cancer (adjusted rate ratio = 1.34, 95% confidence interval 1.06-1.69). This excess risk did not increase over time; women who were exposed more than 35 years ago (rate ratio = 1.35, 95% confidence interval 0.97-1.87) were not at greater risk than women who were exposed within the past 35 years (rate ratio = 1.39, 95% confidence interval 1.01-1.93). The positive association was not observed in women who used diethylstilbestrol before age 25 years but was seen at all other ages. The age of study participants did not modify the association between exposure and breast cancer, and there were no significant interactions between ever use of diethylstilbestrol and any of the other potential risk factors included in the analysis.

These findings are consistent with those of several other studies of diethylstilbestrol exposure and breast cancer.


  • Diethylstilbestrol and risk of fatal breast cancer in a prospective cohort of US women, American journal of epidemiology, NCBI PubMed PMID: 8823060, 1996 Oct 1.
  • Featured image Sandy Millar.