The first wave of hormone pregnancy test litigation
In 1983, the first tranche of litigation in relation to hormone pregnancy tests came to an end. The victims alleged that birth defects had been caused by their mothers taking a hormone-based pregnancy testing drug. The claim failed when legal aid was withdrawn.
The Defendant manufacturer sought to have the action dismissed, which meant it could not be revived. The judge, Mr Justice Bingham, allowed the Claimants to discontinue. However, he stated that a future action would only be permitted if there was something akin to “a scientific revolution”.
The second attempt to achieve justice
Nearly four decades later, the victims again sought to achieve justice. They were promised a remorseless pursuit of the same by their lawyers, Pogus Goodhead, who withdrew funding when faced with a strike out application Again, the claims could not proceed.
From “Scientific Revolution” to scientific paradigm shift
With respect to that great Judge, ‘scientific revolution’ may be not the most appropriate term. Perhaps a “paradigm shift” is more accurate. Significant advances in scientific understanding do not always occur in a sudden and dramatic way. Rather, there can be an accretion of knowledge leading to a different understanding.
A new publication by prominent researchers from USA , Australia, and Sweden, could be described as representing the culmination of a paradigm shift.
The genome era and the changing understanding of birth defects
Historically, it was very difficult to distinguish between birth defects that were genetic; that is within the DNA of the victim or environmental which includes toxic; that is caused by an insult during pregnancy. As the authors describe in their paper, the genome era has produced much greater understanding of the mechanisms of birth defects.
RCEM: A new framework for understanding toxic birth defects
In 2020, world leading geneticists including Margaret Adam, a co-author of the current paper published a study on identical twins where one twin had a birth defect but the other did not. It was therefore reasonable to conclude that the birth defects in question were not genetic. They found a distinct pattern of toxic birth defects, which they described as recurrent constellations of embryonic malformations (RCEM). Subsequent studies have built on the understanding of RCEM, which is now accepted widely by geneticists.
The new study: Analysing the MHRA Expert Working Group Data
The present study looked in particular at a group of 225 cases which had been obtained for the Expert Working Group reporting to the MHRA in the UK in 2017. Analysis of this group shows that the defects could reasonably be considered part of the RCEM spectrum; therefore toxic, not genetic.
Vascular disruption and the link with Misoprostol
The paper references earlier work by Professor Danielsson (a co-author of the current paper) and others in 2023 and 2025. By analysis of the birth defects seen with HPT and Misoprostol, Professor Danielsson was able to conclude that the similarity was such that it was reasonable to accept that HPT defects had been caused by vascular disruption in early pregnancy. That Misoprostol taken in early pregnancy to induce abortion caused such defects through vascular disruption when pregnancy continued to live birth is widely accepted, including by the EWG group in 2017.
Scientific evidence supporting the RCEM interpretation
That the birth defects seen with HPT use are similarly caused by vascular disruption is supported by a raft of scientific evidence:
- First, the pattern of defects is pathologically consistent with those expected with an insult in early pregnancy. This is the period of organogenesis when the organs and the limbs develop. The spectrum includes conspicuously limb reduction defects and VACTERL syndrome (where multiple organ defects are reported).
- Secondly, as the authors point out, it is consistent with the results of animal studies.
- Thirdly, the epidemiological studies on HPTs have shown a clear association, in particular between the defects in the RCEM spectrum and HPT use.
Criticism of the MHRA Expert Working Group Report
The data gathered for the EWG Report can now be seen as consistent with RCEM. The EWG could not in 2017 have identified the RCEM spectrum. However with proper evaluation they should have identified that the HPT defects were toxic. They failed to compare the HPT group with misoprostol cases. They did not consider the pattern of multiple defects. They dismissed the epidemiological papers which all showed an association as being due to chance or confounding factors. They took this approach even where studies such as those on limb reduction defects and VACTERL syndrome which they acknowledged were of good quality identifying a clear raised incidence with HPT’s.
The MHRA’s response to emerging research
The MHRA remain adamant in seeking to defend the deeply flawed EWG report. When the Committee for Safety of Medicines, a part of the MHRA, reviewed the 2023 paper by Professor Danielsson in 2025, they were only able to discuss it in superficial terms “A fascinating hypothesis”. Neither the Committee nor the scientists advising them showed any real insight into the issues raised. It would appear that at no stage have MHRA scientists undertaken the basic exercise of comparing defects in the HPT group with those in the Misoprostol group.
Transparency and access to evidence
The MHRA also sought to obstruct the research for the present paper. When FOI requests were made for a redacted case reports held by the MHRA, these were refused. A number of contradictory and absurd excuses were given. The MHRA suggested that all the information was already available but also that it could not be disclosed because it was confidential. They relied on data protection even though the case reports were sought in redacted form. Some of the case reports in redacted form appear in an annexe to the EWG report. This issue has now been referred to the Information Commissioner.
A long overdue review?
The present paper is scientific evidence of the highest quality by world leading experts. They do not undertake their research for financial or any other secondary gain. They are simply seeking to advance scientific understanding. This should be treated with respect. The Government, when it commissions the long overdue review of the scientific evidence on HPTs, should ensure that it is entrusted to authoritative and unbiased individuals.
