International Association Against Painful Experiments on Animals

101 Misleading results from Vivisection Animal Experiments

59: Daughters of DES

On the basis of animal experiments, the synthetic oestrogen diethylstilbestrol (DES) was suggested as a means of preventing miscarriage.(1) Although no proper human (clinical) trials were carried out,(2) the procedure nevertheless became widely accepted, and between 1948 and 1971, DES was given to some 2-3 million pregnant women in the US alone.

However, DES was ineffective. In 1953, properly controlled clinical trials showed that DES did not work.(3) Tragically, the study failed to report that DES increased abortions, neonatal deaths and premature births, a conclusion that could have been made from the data available in the trial.(4) DES was not only ineffective, it was also unsafe. Just how unsafe was only revealed in 1971 when researchers traced a link between exposure to DES and a previously rare form of vaginal and cervical cancer in daughters of women who had taken the drug during pregnancy.(5) Almost 600 cases have been reported (6) but DES has proved a biological timebomb as side-effects continue to surface in sons and daughters of women who took the drug.

It has been suggested that animal tests provided an early warning of the problems. It is true that in 1938 DES was found to cause breast cancer in male mice, but since the cancer-causing potential of other oestrogens varied according to the strain of mouse used,(7) the results could hardly be a serious basis for action. Furthermore, the consensus among animal researchers at the time was that oestrogens did not produce cancer,(7) rather they gave male mice mammary glands and thus made them susceptible to the same cancer-causing factors that operated within female animals. In fact, a summary of the animal data in 1941 found "only meagre evidence" that oestrogens cause cancer of the cervix.(7) Not until the 1970s did it become clear that in contrast to the majority of animal experiments, DES was a potent cause of cervical cancer in women.


1) Health Action International, “Problem Drugs” pack, 1986, May 13
2) D.Brahams, Lancet, 1988, October 15, 916.
3) W.J.Dieckmann et al, American Journal of Obstetrics & Gynaecology, 1953, vol.66, 1062-1081.
4) Y.Brackbill & H.W.Berendes, Lancet, 1978, September 2, 520.
5) A.L.Herbst et al, New England Journal of Medicine, 1971, April 22, 878-881.
6) C.Vanchieri, Journal of the National Cancer Institute, 1992, vol.84, 565-566.
7) S.Peller, Cancer in Man (McMillan, 1952).

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