Mrs R, a heavy smoker, had taken the combined oral contraceptive pill in various formulations since the mid-1960s. She had been issued with repeat prescriptions for this by Dr T, her GP. During this time her records showed no evidence of assessment of her suitability for this form of contraception, in terms of its effect on her cardiovascular risk profile.
There was no record of her BP ever being checked, of other risk factors being assessed, or advice being given on smoking.
Unfortunately Mrs R suffered a cerebral lacunar infarct in her late forties, leaving her with a dense right hemiparesis. Diabetes was diagnosed during her hospital admission.
She sued Dr T, alleging that he had been negligent in prescribing the pill to her for such a prolonged period without assessing her risk of stroke.
Several GP experts were critical of the way that Dr T had issued prescriptions for the combined pill without apparent consideration, or assessment, of cardiovascular risk factors. It was clear that there had been a breach of duty. However, we received differing assessments on whether or not a causal link to her stroke could be established.
Epidemiological experts said that the literature showed conflicting evidence as to an increased risk of stroke in women taking the combined oral contraceptive pill. Even if this point were clear, there was no reliable way of determining what the effect of taking the pill would be in an individual who already had an adverse risk profile. The epidemiological evidence was insufficient to answer this question.
An expert in the epidemiology of stroke was instructed by the court to give an estimate to this question, on the balance of probabilities. He estimated that the pill had made a 10% contribution to Mrs R’s risk of suffering a stroke, a contribution he considered to be ‘minimal’ in terms of causation.
However, legal advice was that it was likely that a court would consider this contribution to be ‘materially relevant’. Any statistical arguments apparently lessening the impact of the pill might be shown to be flawed. On this basis we entered into negotiations with Mrs R’s counsel, in the light of the uncertainties of the case, to reach a fair settlement of her claim. She received a sum equivalent to £180,000 (US$320,000) to help fund her care needs.
Stroke and the pill – Debate continues about the effect of the combined oral contraceptive pill on the risk of stroke. There is no clear consensus on what the population data say about the correct clinical approach in prescribing the pill to those with other cardiovascular risk factors.
A useful review paper is Chan WS et al., Risk of Stroke in Women Exposed to Low-Dose Oral Contraceptives: A Critical Evaluation of the Evidence, Arch Intern Med,164(7):741–7 (2004). Bandolier’s website has a useful examination of the evidence and illustrates the difficulty of assessing risk in this context.
Clinicians should bear in mind that the association is uncertain and relative, but should show that they have considered the risk in individual cases and advised their patients as best they can.