Montgomery and informed consent

Explaining informed consent and the significance of Montgomery vs Lanarkshire Health Board.

  • When seeking consent to treatment, the question of whether the information given to a patient is adequate is judged from the perspective of a reasonable person in the patient's position.
  • For the purposes of consent, the ruling from Montgomery replaces the previous tests founded in Bolam and refined in Sidaway.
  • Doctors have a duty to take reasonable care to ensure that patients are aware of 'material risks'.

Montgomery vs Lanarkshire Health Board: background

  • Nadine Montgomery's son was born with cerebral palsy as a result of shoulder dystocia during birth.
  • Mrs Montgomery was around five feet tall, and was also diabetic, which often results in a larger foetus. She had raised concerns that her baby might be too big to be delivered vaginally, but had not asked about 'exact risks'.
  • Evidence showed a 9-10% risk of dystocia where a diabetic woman gives birth via vaginal delivery, but Mrs Montgomery wasn't warned of the risk of shoulder dystocia, or offered a caesarean section as an alternative.
  • The treating obstetrician felt that if Mrs Montgomery was told of the risk she would opt for a caesarean, and didn't believe this was in her best interest.
  • It was accepted that shoulder dystocia can cause serious complications for mother and baby but also accepted that the risk of cerebral palsy was low, at around 0.1%.
  • Mrs Montgomery claimed for negligence, arguing she should have been told of all the risks.
  • She was awarded over £5 million in damages, after an appeal went to the Supreme Court.


Before Montgomery, a doctor's duty to warn patients of risks was based on whether they had acted in line with a responsible body of medical opinion. This was known as the Bolam test.

The court accepted that if Mrs Montgomery been told about the risk of dystocia, she would have chosen to have a caesarean. Her appeal was successful and the judgment held that the assessment of whether consent was adequate in a clinical negligence claim would not be assessed by the Bolam test.

Instead, doctors must provide information about all material risks; they must disclose any risk to which a reasonable person in the patient's position would attach significance.

The judgment therefore means that doctors must share all such material risks, as well as any it would be reasonable for them to think the individual patient would attach significance.

GMC guidance

Although Montgomery changed the legal position, the principle of involving patients in their treatment and sharing information with them about risks has been in place for some time.

In its guidance Decision making and consent (2020), the GMC advises that doctors must try to find out what matters to patients so they can share relevant information about the benefits and harms of proposed options and reasonable alternatives, including the option to take no action.

The GMC advises doctors to tailor the discussion about potential benefits and harms to each individual patient, being guided by what matters to the patient and sharing information in a way they can understand.

Paragraph 23 of the guidance states that you should usually include the following information when discussing benefit and harms.

  • Recognised risks of harm that you believe anyone in the patient's position would want to know. You'll know these already from your professional knowledge and experience.
  • The effect of the patient's individual clinical circumstances on the probability of a benefit or harm occurring. If you know the patient's medical history, you'll know some of what you need to share already, but the dialogue could reveal more.
  • Risks of harm and potential benefits the patient would consider significant for any reason. These will be revealed during your discussion with the patient about what matters to them.
  • Any risk of serious harm, however unlikely it is to occur.
  • Expected harms, including common side effects and what to do if they occur.

Material risks

The key passages from the Montgomery judgment involve what a patient would consider to be material risk:

"The doctor is therefore under a duty to take reasonable care to ensure that the patient is aware of any material risks involved in any recommended treatment, and of any reasonable alternative or variant treatments.

"The test of materiality is whether, in the circumstances of the particular case, a reasonable person in the patient's position would be likely to attach significance to the risk, or the doctor is or should reasonably be aware that the particular patient would be likely to attach significance to it."

- Judgment in Montgomery v Lanarkshire Health Board [2015] UKSC 11, paragraph 87.

Some other key points were:

  • whether a risk is material doesn't only depend on how frequently it occurs
  • your advisory role involves talking to the patient to make sure they understand the risks and benefits of their treatment, so that they can make an informed decision
  • simply providing the information or getting a signature on a consent form may not be enough to evidence proper consent, but can be helpful as part of the consent process.

Therapeutic exception

In a situation where being given this information would be seriously detrimental to the patient's health, the Supreme Court ruled that it can be withheld.

However, this is a limited exception and it's likely that it will only be applicable in very rare circumstances.

Consent and capacity

Patients must have the necessary capacity to give valid consent. In England and Wales, the Mental Capacity Act (2005) (MCA) is used and sets out a statutory test, which says that to be able make a decision, the patient must be able to:

  • understand information relevant to the decision
  • retain that information
  • use or weigh it as part of a decision, AND
  • communicate their decision effectively, by any means.

The MCA makes clear that patients should be presumed to have capacity unless it can be established otherwise.

Remember also that capacity is both time and decision specific.

Scotland and Northern Ireland

The Adults with Incapacity Act (2000) governs assessing capacity in Scottish law.

In Northern Ireland, the common law still applies with respect to capacity. There is a Mental Capacity Act (Northern Ireland) (2016) but the provisions of the Act are not yet in force.

This page was correct at publication on 30/01/2024. Any guidance is intended as general guidance for members only. If you are a member and need specific advice relating to your own circumstances, please contact one of our advisers.

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