London’s High Court has struck out a bid by scores of British families to sue pharmaceutical company Schering (now owned by Bayer) – former manufacturer of hormone-based pregnancy test Primodos – who claim their babies were harmed by the test, one dose of which contained about 40 times the level of hormones in modern contraceptive pills.
Scientists first published concerns about birth defects in the 1960s, a decade before the tests were withdrawn, but the evidence for a causal link remains contentious, reports The Guardian.
Primodos was introduced to the UK in the late 1950s, and involved taking two pills on consecutive days containing norethisterone, a synthetic progesterone, and ethinyl estradiol, an artificial oestrogen. If a woman was not pregnant, the pills would trigger a period, meaning no bleeding indicated pregnancy.
Why was it withdrawn?
In 1967, Isabel Gal, a paediatrician at Queen Mary’s Children’s Hospital in Surrey, published findings suggesting a link between Primodos and birth defects. The study, a survey of 100 mothers whose babies had been born with congenital abnormalities, found that 19 of the women, compared with four in a control group, had used the pregnancy test drug.
After concerns were raised, Schering removed pregnancy testing as one of the uses of Primodos, stating it should be used only to treat irregular periods. The drug was voluntarily withdrawn from the market in 1978 for commercial reasons.
Evidence for a link between the drug and birth defects?
Since Primodos was withdrawn, other studies, including a 2018 systematic review by Oxford scientists, have reported a statistically significant association between the tests and congenital abnormalities, including neural tube and heart defects. However, the issue remains contentious.
In 2017, the expert working group of the UK’s Commission on Human Medicines published a detailed report that concluded that the available scientific evidence “does not support a causal association between the use of hormone pregnancy tests, such as Primodos, during early pregnancy and adverse outcomes, either with regard to miscarriage, stillbirth or congenital anomalies”.
Animal studies have also produced mixed results. Schering denies there is a link.
A fundamental issue is that the way data was collected when the drug was in use was far less robust than safety trials today. Some of the studies relied on mothers’ memories of when in pregnancy they took the drug, for instance.
Timing of exposure is crucial for drugs that have been established to cause birth defects, such as thalidomide. A very large, robust dataset would make it far easier to definitively establish whether the babies of women who took the tests had a higher chance of birth defects than the roughly 3% background rate – and whether the link was causal.
High Court ruling
More than 100 families who believe they have suffered harm due to Primodos were hoping to bring a civil case against Bayer. A case in 1982 had failed after it was judged to be unlikely that the claimants could prove a causal link. The latest judgment concludes that since then “the position has not materially changed in the claimants’ favour”.
The judge acknowledged the ruling was unlikely to dissuade the families, some of whom have been campaigning for decades, of their case for compensation.
“I recognise the profound disappointment my judgment will bring for the claimants,” she said. “They believe … that HPTs (home pregnancy tests) were the cause of the birth defects and the loss of the babies which they have suffered. No one has been able to confirm definitively that this belief is wrong.”
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