CNZ v Royal Bath Hospitals NHS Foundation Trust and (2) Secretary of State for Health and Social Care


In January 2023, Mr Justice Ritchie handed down an important decision dealing with Montgomery and causation in birth injury claims.

The relevant findings of fact:

  1. The Claimant was born in a very poor state at 01.03 on 3 February 1996. She was a twin and her sister was born about an hour before her.
  2. She had suffered acute profound hypoxic ischaemia (PHI) for between 14 and 18 minutes duration (mid point 16 minutes).
  3. 3 minutes of that PHI occurred after her birth until she was resuscitated at around 01.06.
  4. The acute PHI caused the Claimant’s cerebral palsy.
  5. Fetal bradycardia was occurring from around 00.50 (the mid point of 00.48 to 00.52).

The Claimant’s case:

  1. Her mother requested caesarean section (CS), but her requests were refused or delayed. In addition, her mother was never offered elective caesarean section (ECS) despite it being a reasonable treatment option.
  2. When the hospital finally decided to deliver the Claimant by CS, the operation was carried out negligently late. That caused or materially contributed to the development of her acute PHI.

The Defendants’ case:

  1. In 1996, ECS was not a reasonable treatment option to offer during the antenatal period. Therefore, it was not offered. Offering and advising normal vaginal delivery was the correct practice and the Claimant’s mother did not request caesarean section antenatally.
  2. There was no negligence during the labour and the parents’ requests for CS were granted in a timely way.

At trial, the judge heard evidence from a series of highly respected experts with considerable experience in medico-legal work in this field, including:

  1. Mr Forbes and Mr Tuffnell (Consultant Obstetricians).
  2. Dr Newton and Dr Rosenbloom (Consultant Paediatric Neurologists).
  3. Dr Dear and Dr Fox (Consultant Neonatologists).


In a judgment that runs to over 100 pages, Mr Justice Ritchie dealt in detail with questions of informed consent and causation in birth injury claims.

Montgomery – The antenatal period

Given the Claimant’s mother’s obstetric history, she argued that she did not want either artificial rupture of membranes (ARM) or an epidural. Her case was that she had been refused an ECS in the antenatal clinic. This allegation was defended on the basis that: (a) no such request had been made; and (b) in 1996 the standard management for twins where there had been previous vaginal delivery and no concerns about fetal position was vaginal delivery (NVD). Therefore, it was argued that ECS was not a ‘reasonable alternative treatment’.

The judge queried how far back Montgomery actually applied. Acknowledging that this judgment was based on changing societal attitudes to consent which were premised on greater personal autonomy and access to information (particularly from the internet), he found that it applied as far back as 1996. However, he questioned whether it applied much earlier than about 1993.

It applied to the 1999 events in the case, but how far back can this decision be taken? I doubt it can be taken as far back as the 1950s or 1960s. I make no decision on those decades. I wonder if it could be applied to clinical practice in the 1980s. Again I make no decision on that question. As for the 1990s, taking into account the rationale expressed for the movement from paternalism to patient choice there may be a tipping point at which the growth of the internet (Berners-Lee released his system in 1993), the changes in societal values and GMC guidelines and the passing of the Human Rights Act 1998 and other legislation came together to generate the change from paternalism to patient choice. So does Montgomery apply to the facts of this case in February 1996, two years before the passing of the Human Rights Act 1998 and before the internet had really developed much? I admit that I am troubled by this. I consider that it probably does. I have considered whether a watered down form of the ruling would have applied or whether a tapered growth of the Montgomery duty to consent properly could be the correct approach in 1996 but I do not consider I am permitted to do so as a Court of first instance without an indication for such in the Supreme Court’s judgment.

Ultimately, the judge found that the antenatal consent process was reasonable and lawful for medical practice in 1996. He found that CS was discussed with the parents and they agreed to NVD with IOL and as little intervention as possible. Therefore, the claim failed in this regard.

However, he considered that:

There is an inherent illogicality in the approach taken by the 1st Defendant’s department. All of the Defendants’ witnesses and Mr Tuffnell asserted that ECS was not a reasonable treatment option antenatally for M because she had achieved NVD twice before, was healthy and her twins were in a cephalic position and healthy. But they all also gave evidence that if M had requested CS (CSMR) and persisted, despite being put through two or perhaps three counselling sessions against that choice, they would and should have agreed to her choice for CS as her birth plan. Such agreement must in logic mean that CS was a reasonable medical treatment option for M despite being more risky for her. Indeed the undisputed evidence was that in 1995-1996 42% of twin births were by CS. In my judgment it is not logical for the Defendant to assert that CS was an unreasonable treatment option in the face of those matters.

Therefore, he found that CS was a reasonable treatment option. This raises an issue of some importance. Even if there is a Trust policy in place not to offer a particular treatment option as standard management, if a patient would ultimately be given such treatment if they fought hard enough for it, logic dictates that it must be a reasonable treatment option which should be discussed with the patient. In another case with another mother where CS was not discussed, the ‘illogicality’ of the department’s policy might have produced a different result.

The delivery of the Claimant

In summary, it was found that:

  1. The crucial period relevant to the allegations was between 00.25 and 01.03 (a period of 38 minutes).
  2. There was a negligent delay of 6.5 minutes in delivering the Claimant.
  3. At 00.25 / 00.26, there was a negligent failure to discuss the necessary reasonable treatment options (including CS and ARM) and the associated risks and benefits with the parents. In short, Montgomery applied even in circumstances where the need for treatment was imminent and time was of the essence:

I consider that Mr Forbes’ criticisms of Doctor Tristram at this point are reasonable and valid. I consider that what all reasonable doctors would have done is to set out the options, the risks and benefits and to seek the parents’ choices on those options before going to the consultant. In my judgment Montgomery applied at this point. Doctor Tristram needed to know, before she checked with the consultant, what the parents’ choices were. To obtain their informed choices she needed to inform them of the risks and benefits of the options of CS or NVD with possible ARM (low and high). She should have given them the right to choose CS and asked whether they would accept low or high ARM or ARM at all in the absence of EA.

At 00.35, a further discussion took place and there were similar failures. It was found that the parents had made a clear choice for CS but this was ignored. There was a failure to act on their decision and to act urgently in taking the Claimant’s mother to theatre. The clinician was criticised for taking it ‘slowly’:

I accept the Claimant’s criticism of this approach as too paternalistic. Patient choice was being ignored at this stage. Doctor Tristram was, on her own evidence, proceeding slowly with ARM without having obtained permission to do a high one and she did not record M’s permission to do so. The parents were requesting CS and in my judgment at that time in the circumstances Doctor Tristram should have agreed to that request (subject to reassessment to see if the baby’s head had descended so far that CS was no longer the right option once they were in theatre).

It was held that the total negligent delay was between 5 and 8 minutes (mid point of 6.5 minutes). The Claimant should have been delivered by 00.55 to 00.58. This would have been within the non-damaging 10 minute period of PHI.

This application of Montgomery in the context of an imminent delivery rather than antenatally is different to how previous Courts have dealt with this issue (see ML v Guy’s [2018] EWHC 2010). Mr Justice Ritchie explained that the difference in this case was that the Claimant’s father was in the delivery room at 00.26 and able to speak for the Claimant’s mother and they both chose CS which they had made clear. Whether Montgomery applies in the context of an imminent birth where a mother gives birth alone in the absence of a birthing partner is therefore unclear. This appears to be fact specific rather than generating a new principle of wider application. However, in recent times where the impact of Covid-19 has seen a significant limitation on who can attend the delivery room, this decision potentially creates a different standard of consent for those mothers giving birth alone and those who have someone in the room who can speak on their behalf.


In summary, it was found that:

  1. On the balance of probabilities, the duration of the acute PHI was 14 to 18 minutes (midpoint 16 minutes).
  2. The Claimant was suffering bradycardia during those 16 minutes which is likely to have started between 00.48 to 00.52 (midpoint 00.50).
  3. The agreed expert evidence was that the first 10 minutes of acute PHI are not generally damaging. However, the minutes thereafter (minutes 10 to 16 in this case) cause increasing or incremental brain damage. Therefore, it was held that there were around 6 minutes of damaging PHI.
  4. Had the 6.5 minutes of negligent delay not occurred, the Claimant would have been born at 00.56 / 00.57 by CS. This would have been within the non-damaging 10 minute window.
  5. Therefore, on the findings of fact, all of the Claimant’s brain injury was caused by the negligence and ‘but for’ causation was satisfied.

However, at the extreme ends of the range of the factual findings, earlier delivery would have avoided some but not all of the damage. It was here that the judge was troubled most. He conducted a detailed analysis of the authorities concerning ‘but for’ causation and material contribution.

To assess the quantum attributable to the negligence, the Court needed to decide what the Claimant’s functional outcome would have been but for the negligent delay.

The judge held that, in the context of acute profound hypoxic ischaemia, every minute counts:

The agreed evidence was that every minute of acute PHI over the first 10 minutes caused increasing or incremental brain cell deaths which could number in the tens or hundreds of thousands. I find that this damage minute by minute was more than de minimis.

I find on the evidence before me, that medical science is unable to identify with generality, accuracy or detail the functional effect of each minute of brain cell deaths. Both experts, Doctor Newton and Doctor Rosenbloom, advised that they could not predict the pattern or severity of the resulting functional disability from a minute by minute increase in the duration of the PHI suffered.

On the basis that there is no linear relationship between minutes of acute PHI and functional outcome, the judge found that medical science was unable to identify with generality, accuracy or detail the functional effect of each minute of brain cell deaths. It was scientifically impossible. Therefore, the Claimant was entitled to recover 100% of the damage caused by the PHI on the basis of the material contribution test.

In doing so, the judge rejected the ‘Aliquot theory’ advanced by Dr Lewis Rosenbloom on behalf of the Defendant. In short, Dr Rosenbloom argued that the likely functional outcome caused by acute PHI could be broken down into 5 minute blocks of time (or aliquots). In that way, a Court could assess the level of disability that the Claimant would have had in any event. The judge rejected this theory, partly because there was insufficient evidence to support the proposed distinctions:

Thus in my judgment the Aliquot theory, honestly and helpfully put forwards, as it was, by an impressive and experienced expert, is not an acceptable, fair or practicable way to apportion quantum in this Cerebral Palsy case caused by acute PHI.

However, he considered that, if fairness was the only test, the Court should apportion quantum so that a Defendant is only liable for the brain damage which it caused and not that which would have occurred in any event. He suggested that a fair way to apportion damages would be by way of a percentage based on the relative durations of the PHI caused by the negligent delay compared to the PHI which would have been suffered in any event.

In exploring whether an apportionment was possible in this case, the judge conducted a detailed analysis of how a Court should approach ‘indivisible’ vs ‘divisible’ injuries. He drew a distinction between: (a) ‘trigger’ injuries; and (b) injuries that are ‘dose related’ and therefore divisible:

I do not consider that the term indivisible applies to the Claimant’s brain injuries in this case. An indivisible disease is one which starts when triggered and then goes on and gets worse or takes its course whatever the exposure to the noxious substance after the triggering event. These diseases are not divisible in the sense that they are not reduced by stopping the exposure and do not get worse on increasing the exposure. They start and then they progress, like cancer or mesothelioma.

Brain damage caused by PHI is not a trigger disease. It does not grow like cancer or mesothelioma once triggered. The spread of brain damage due to PHI is wholly dose dependent. The more PHI the fetus suffers the greater the brain damage. However the word indivisible may apply to the functional outcome caused by one or more minutes of acute PHI.

Whilst the judge was clearly attracted to the fairness of an apportionment of quantum based on a percentage tied to the relative duration of acute PHI, he ultimately summarised his analysis of the law as follows:

I accept that there is a distinction to be drawn between impossibility of proof for apportionment of functional outcome and difficulty over proof for apportionment of functional outcome. The dividing line depends on the evidence. I consider that in the case before me, where the Claimant’s cerebral palsy has been caused by one noxious factor: acute PHI, and where the agreed medical evidence is that every minute of PHI caused increasing brain damage, the scientific gap is how to attribute the breach PHI (or each minute of brain damage) to each or any functional deficit.

In law I consider that the cases I have reviewed above show that if there is a scientific gap making proof of causation of functional outcome, therefore also quantification, impossible in contra-distinction to merely difficult, then the Claimant will recover 100% of the damage she has suffered due to the acute PHI so long as the Claimant can prove that the breach made a material contribution to the reduced functional outcome which was more than de-minimis.

However, in cases involving divisible (‘dose related’) injuries, where the evidence allows the functional outcome to be attributed in percentage proportions to the negligent and non-negligent causes, the judge’s clear view was that there should be an apportionment.

Material contribution is an ever-developing area of clinical negligence work. However, the question of when an apportionment should and should not be applied may well be the next hotly contested chapter in its evolution.

This is another important case for practitioners who undertake clinical negligence work to get to grips with.