The daughters of the thousands of women who took an anti-miscarriage pill more than 40 years ago are at increased risk of breast cancer, it was revealed yesterday.

The drug, known as DES (diethylstilbestrol), was commonly prescribed for pregnant women between the 40s and 60s if doctors thought they were at risk of miscarrying and sometimes also for morning sickness. There are no definite figures for the number of women who took it, but research suggests there may have been as many as 200,000 in the UK.

A study, published in the journal Cancer Epidemiology, Biomarkers and Prevention, has found that the daughters of women who took DES have almost double the risk of breast cancer of their peers and the more their mothers took, the greater their chance of developing the disease.

DES is a synthetic oestrogen - the hormone associated with maintaining pregnancy and also with the growth of some tumours. The American scientists who carried out the research said the "DES daughters" should think twice before using hormone replacement therapy which would boost their oestrogen levels again.

"This is really unwelcome news because so many women worldwide were prenatally exposed to DES and these women are just now approaching the age at which breast cancer becomes more common," said lead author Julie Palmer, professor of epidemiology at the Boston University's school of public health.

Alarm over the side effects of DES was generated in the early 1970s. First it was discovered that one in 1,000 girls born to women who had taken it were likely to develop a particular vaginal cancer.

Then it was found that the women who had taken it had an increased risk of breast cancer. The drug is no longer used in the developed world, except for prostate cancer.