Pregnancy test drug had the potential to deform embryos

The components of a controversial drug, allegedly linked to birth defects in the 1960s and 70s, had the potential to deform embryos in the womb.

Primodos was a hormone pregnancy test used by thousands of women in the UK between 1958 and 1978.

It was found to cause deformations to fish embryos just hours after they received a dose in new studies by researchers at the University of Aberdeen.

Researchers at the time suggested the drug could be linked to a higher risk of women giving birth to babies with abnormalities – a claim denied by Primodos’ manufacturer.

Although Primodos is no longer in use, its components (Norethisterone acetate and Ethinyl estradiol) are used in other medications today including treatments for endometriosis and in contraceptives.

In November last year a UK government expert working group (EWG) study found no “causal association” between the drug and the abnormalities, stating that outdated methods used by scientists in the 1970s was partly responsible for a failure to find a connection.

A new study at the University of Aberdeen, published yesterday in the Scientific Reports journal, reveals more about the effects of Primodos’ components on the embryos of zebrafish.

The paper outlines how, after the components of Primodos were added to water around zebrafish embryos, their movement slowed down rapidly; developed changes to the heart within four hours; and within 24 hours displayed damage to tissues such as the fins, eyes and spinal cords.

More surprisingly, according to the researchers, the study showed that the drug accumulates in the zebrafish embryo over time.

They suggest that, if this also occurs in a mammalian species, even a seemingly low dose of the drug for the mother could result in much higher levels for the embryo.

This latest study was led by Dr Neil Vargesson, who has also published extensive research into thalidomide – a drug used in the 1950s to treat morning sickness but which caused thousands of babies worldwide to be born with malformed limbs.

He said: “At the moment the scientific research into whether or not Primodos caused these birth defects is inconclusive.

“What this study highlights is that there is a lot still to be learned about Primodos and more widely its components effects on mammals.”