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The Primodos Story

written by Carl Heneghan, Nuffield Department of Primary Care Health Sciences, University of Oxford  

Fifty years ago high strength hormones, such as Primodos were used as a test for pregnancy. Containing ethinylestradiol and very high doses of norethisterone, they were given to over a million women from 1958 to 1978, when Primodos was withdrawn because of concerns about teratogenicity.

These concerns over increased risk of congenital malformations led to considerable controversy. That is until we published in Version 1 of a systematic review and meta-analysis in F1000 on ‘Oral hormone pregnancy tests and the risks of congenital malformations’ (version 2 accepted in Jan 2019)

This review showed that oral HPTs in pregnancy were associated with increased risks of several congenital malformations. We found 16 case-control studies and ten prospective cohort studies, including 71 330 women, of whom 4,209 were exposed to the tests.

Our review has created considerable interest amongst those affected, and at a governmental level. What follows is a short summary of what has been happening since we published our review.

On November 28th, 2018, I presented the results to the All Party Parliamentary Group on Hormone Pregnancy Tests at the UK Houses of Parliament; and submitted the review evidence to the Independent Medicines and Medical Devices Safety Review (IMMDS)  Chaired by Baroness Julia Cumberlege, I presented the findings to the review panel in December. The IMMDS review should be out later this year.

The review also featured in Prime Minister’s Question on January the 16th of this year when Yasmin Qureshi MP, asked direct questions about the review findings at  PMQs. Theresa May said “ministers are aware of the new study that has come out” and it will be “looked at very carefully.” The review has also featured in the German Parliament where Jeff Aronson presented the results, and twice it has been the subject of Sky news documentaries: ‘A groundbreaking study from Oxford University has linked the pregnancy test drug Primodos to malformations in babies born to mothers who used the drug.’

On the 23rd April, a House of Commons Debate took place based on the review findings. And because there is so much going on, we have summarised the timeline of the Primodos Story to keep you up to date. 

Marie Lyon, who posted a patient perspective on the CEBM site, said "The review once published was particularly important to our members, to prove the science did exist to show an association between HPT’s and adverse effects." 

If you are interested in knowing more Sky News provides the backstory to the issues that led to our review.


The review is funded by the National Institute for Health Research School for Primary Care Research (NIHR SPCR) [Projectumber 390] and is part of the Evidence Synthesis Working group (ESWG), a collaboration of all nine primary care member departments of the School of Primary Care Research. CH is funded by the (NIHR SPCR ESWG [Project Number 390], the NIHR Oxford BRC and is an NIHR Senior Investigator.

The views expressed are those of the author(s) and not necessarily those of the NIHR, the NHS or the Department of Health. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Links to further information

Heneghan C, Aronson JK, Spencer E et al. Oral hormone pregnancy tests and the risks of congenital malformations: a systematic review and meta-analysis [version 2; peer review: 3 approved]. F1000Research 2019, 7:1725

Oral hormone pregnancy tests and the risks of congenital malformations: a patient perspective Marie Lyon.


Evidence Synthesis Working group (ESWG)