A template for defining a causal relation between acute intrapartum events and cerebral palsy: international consensus statement
BMJ 1999; 319 doi: https://doi.org/10.1136/bmj.319.7216.1054 (Published 16 October 1999) Cite this as: BMJ 1999;319:1054
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The template of MacLennon et al has I believe given a voice of reason
to the unabated medicolegal free for all that has surrounded the
discussion of causation of cerebral palsy. Whilst not a member of the
group who developed the template I have found it to be of great assistance
in approaching cases that have required an opinion. As such this template
builds on the previous work of Nelson and many others with respect to
associations between birth events and neurological outcomes and the now
well documented lack of usefulness of fetal heart rate monitoring and
neurological outcomes.
References.
Nelson KB (1989) relationship of intrapartum and delivery room events
to long term neuroligical outcome. Clin Perinatol 16:995
Editorial (1989) Cerebral palsy, intrapartum care and a shot in the
foot. Lancet ii:1251
Stanley FJ, Blair E (1991) Why have we failed to reduce the frequency
of cerebral palsy? Med J Aust 154:623
Freeman R (1990) Intrapartum fetal monitoring - a disapointing story.
N Engl J Med 322:624
Competing interests: No competing interests
Sir,
The MacLennan consensus statement on CP (cerebral palsy)1
harnesses a weight of opinion on a vexed subject, but falls short of the
comprehensiveness and, more importantly, the impartiality expected of the
'Education and debate' section of the BMJ. A declaration purporting to
define a relationship between outcome and intra-partum events for medico-
legal clarity and thereby for the benefit of all involved, including the
public, should for those same reasons, also define the circumstances in
which either a delay in delivery or the use of certain modes of delivery
would fall short of acceptable practice and therefore be indefensible.
Although emphasis is repetitively placed on the greater likelihood of pre-
or post-partum causes being responsible for CP, there is no discussion as
to which of these conditions are in turn preventable by good practice, or
the criteria which would determine culpability if they arose. By omitting
these considerations, adopting a very restricted model of
hypoxic/ischaemic brain injury, changing the terminology from 'foetal
distress' to one less critical, emphasising the rarity of an intra-partum
cause and imposing a virtually unobtainable burden of proof on the
plaintiff, the authors have created for any defendant a blue-print
seemingly endorsed by a leading medical journal. The impact of this
approach is threefold, the first effect being that deserving claims
already within the system are more likely to be denied justice. Of more
concern is the effect on standards of future care, with the possibility of
a less than expeditious approach to even unequivocal signs of foetal
distress, finally following this with an erosion of professional
credibility by then attempting to defend the indefensible.
The rigidity of the template lends itself to more specific criticism,
particularly when the authors themselves acknowledge that the actual
length of time and degree of hypoxia required to produce cerebral palsy in
a previously healthy human foetus is not known and that it is not
currently possible to recognise the point at which cerebral damage becomes
irreversible in the case of an intermittent type of foetal asphyxia. By
acknowledging the possibility of intermittent hypoxia, as for example with
aorto-caval compression, the potential for more normal blood results at
delivery following metabolic correction after restoration of oxygenation
must also be recognised, this despite severe and irreversible cerebral
damage, with parallels following cardiac arrest in the post-delivery
phase. This latter scenario also demonstrates that multi-system sequelae
are not inevitable after hypoxia sufficient for severe cerebral damage,
the brain clearly being the most vulnerable organ, suggesting that this
should be removed as a burden of proof.
The closing recommendations for the use of expert witnesses illustrate a
vested interest in medico-legal practice, yet the above aspects not only
demonstrate a partisan approach within the publication but a lack of the
very impartiality that defines a true expert.
Justice and professional credibility would be better served by defining
good practice in the first instance, rather than providing a template for
the defence of adverse outcomes, in an article that whilst informative,
has the characteristics of a manifesto.
1.MacLennan A. A template for defining a causal relationship between
acute intra-partum events and cerebral palsy: international consensus
statement. BMJ 1999;319:1054-9.
Conflict of interest: none
DR MDD BELL
Consultant in Intensive Care/Anaesthesia
Competing interests: No competing interests
Further criticisms of the recent international consensus (1) and
editorial(2) concerning asphyxia as a cause of cerebral palsy are
justified, supplementing those of Drs Rosenbloom, Rennie, Dear, and
Newell. Asphyxia is best considered as both the cause and effect of
disturbed fetal respiratory physiology, without the unwarranted inclusion
of acidosis and its implications, described by Dear and Newell.
The differing circumstances of asphyxial stress, the varying degrees of
antepartum fetal compromise, and the absence of uniform biological
responses, result in difficulty in accepting the concept of an inflexible
template.
The abilities of imaging to identify the sites of asphyxial injury, the
fetal maturity at the time, and the intervals between injury and
investigation, described by Rosenbloom and Rennie, were unjustifiably
trivialised.
The experimental demonstration more than 50 years ago of impaired uterine
and consequentially placental perfusion during contractions, and its
subsequent confirmation in the human, were not considered (3). Later
investigations over 25 years ago of the neurotoxic effects of asphyxia in
experimentally asphyxiated primates, revealing the significance of long
term partial asphyxial stress, were also overlooked (3).
These deficiencies compromised the credibility of the consensus, which
predominantly relied on epidemiological studies, apparently without the
recognition of their limitations.
Prospective studies suffered from incomplete long term follow up,
retrospective studies could not include those who had already died. It
was formerly not possible to exclude sufferers due to causes other than
that of asphyxia, blurring the precision of determining the prevalence of
asphyxia alone as a cause.
A recently described rate of about 1 per thousand births, similar to that
not associated with obstetrical events observed in the Dublin study, when
compared with two former studies showing rates of over 4 per thousand (3),
belies the assertion of no recent improvement in outcomes (2).
The many clinically important variables of asphyxia and intrapartum care
have not been satisfactorily examined by epidemiologists (3). The
conclusions of a recent Western Australian study of hypoxic ischaemic
encephalopathy (HIE) were invalid for this reason, however in under 8% of
instances had HIE followed an acute asphyxiating event. This
observation suggests that only an equivalently small percentage of
cerebral palsy following intrapartum asphyxia could be attributable to
acute events.
Preoccupation with the outcomes of acute episodes in isolation, together
with the flaws described above, should result in rejection of the
consensus as a balanced overall assessment of intrapartum asphyxia as a
cause of cerebral palsy.
E. L. G. Beavis, FRCS, FRACS, FRCOG, FRANZCOG
Melbourne, Victoria
1 Maclennan A for the International Cerebral Palsy Task Force. A template for defining a causal relation between acute intrapartum events and cerebral palsy: international consensus statement. BMJ 1999;319:1054-9.
2 Bakketeig LS. Only a minor part of cerbral palsy cases begin in labour. BMJ 1999;319:1016-7.
3 Beavis ELG. Asphyxia, cerebral palsy and litigation. Aust NZ J Obstet Gynaecol 1999;39:141-4.
Competing interests: No competing interests
Two issues were not dealt with in the consensus statement about
cerebral palsy, but often arise in medical malpractice trials in the US
that involve children with cerebral palsy. First, lumbar puncture may
disclose an excess of red blood cells, or blood may be visible in a
subarachnoid space on cerebral imaging. Is this consistent or inconsistent
with an hypoxic ischemic event, or not relevant? Second, there are a
number of obstetricians that have used as evidence of hypoxia ischemia the
number of nucleated RBCs present in the infant's blood in the first few
days of life. Does this test have any validity?
Sincerely
Joseph Scheller, MD
Competing interests: No competing interests
The international consensus participants have been content to accept
that to attribute cerebral palsy to prior asphyxia with reasonably
certainty there must be evidence that a substantial hypoxic injury
occurred.1 This is the basis of the claim that in 90% of cases of
cerebral palsy intrapartum hypoxia could not be the cause, despite the
admission of a relationship between spastic quadriplegia and birth
asphyxia. A correlation therefore exists for the severest forms of
cerebral palsy, but not apparently for lesser forms, suggesting that the
sensitivity of tests for brain damage at birth is poor. This is certainly
the case and the spasticity associated with mild cerebral palsy may not
develop for many months.
Simple asphyxia may not be the most important mechanism of birth injury. A
powerful argument in support of a link between cerebral palsy and an
intrapartum event is that cerebral palsy has a strong negative correlation
with elective Caesarian section.2 This procedure avoids the compressive
forces acting on the fetal head during labour
which reduce cerebral blood flow. A temporary reduction of blood flow in
the presence of the lesser degrees of hypoxia typical of the final stage
of labour may well cause reperfusion injury with endothelial damage and
opening of the blood-brain barrier. The resulting oedema and escape of
macromolecules will trigger inflammation and the complement cascade. These
factors may be responsible for damage to the
periventricular areas and the pyramidal tracts which prevents
myelination and results in the delayed development of cerebral palsy.
A third mechanism which may cause intrapartum brain damage is placental
thromboembolism, because the fetal circulation allows blood from the
placenta to avoid pulmonary filtration by passing through the foramen
ovale.3
Ultrasound and MRI have followed the sequence of events from birth to the
development of cerebral palsy as late as 2 years after birth.4 Such long
intervals allow the dissociation of intrapartum events and the development
of cerebral palsy and it is predictable that the lesser forms of injury
show the poorest correlation. Magnetic resonance spectroscopy can
demonstrate hypoxia in infants from the
presence of lactate5 and allow a prospective study of the importance of
hypoxia and ischemia in birth injury. In order to establish the true role
of intrapartum events in neonatal brain injury there must be a full
examination of the mechanisms involved.
Philip James
Senior Lecturer and
Hon. Consultant
References
1. McLennan A. A template for defining a causal relation between
acute intrapartum events and cerebral palsy: international consensus
statement. Br Med J 1999;319;1054-9.
2. Nelson KB, Grether JK. Potentially asphyxiating conditions and
spastic cerebral palsy in infants of normal birth weight. Am J Obstet
Gynecol 1998;179:507-513.
3. Kraus FT, Acheen VI. Fetal thrombotic vasculopathy in the
placenta: cerebral thrombi and infarcts, coagulopathies and cerebral
palsy. Hum Pathol 1999;30:759-69.
4. Dubowitz LMS, Bydder GM, Mushin J. Developmental sequence of
periventricular leukomalacia. Arch Dis Child 1985;60:349-55.
5. Ashwal S, Holshouser BA, Tomasi LG, Shu S, et al. 1H- magnetic
resonance spectroscopy-determined cerebral lactate and poor neurological
outcomes in children with central nervous system disease. Ann Neurol
1997;41:470-481.
Competing interests: No competing interests
Dear Sir,
We write in response to the paper of MacLennan 1 and the editorial of
Bakketeig 2 on the causation of cerebral palsy.
We agree that whenever any individual child presents with one of the
cerebral palsy syndromes, appropriate detailed and meticulous
investigation into why this has happened is needed. We agree also that
only a minority of children with cerebral palsy have sustained their brain
problems as a consequence of intrapartum hypoxic ischaemic damage at term
and that an even smaller number have sustained their problems as a
consequence of an inappropriate standard of care.
We nevertheless have multiple concerns with regard to these two
papers.
Firstly we do not accept the premise that birth asphyxia is commonly
accepted either professionally or at a lay level as being a frequent cause
of cerebral palsy. That view was dispelled some years ago as a consequence
of the work quoted by Bakketeig and it is quite counter-productive to re-
state those arguments.
Secondly we find aspects of the MacLennan article to be wholly
unacceptable. Firstly the implication in Box 1 is that the taskforce he
coordinates has not attracted dissident views. Quite the opposite is true.
We are sure that we are not alone in having resisted invitations to sign
up to this consensus and indeed its signatories do not include any UK
paediatric bodies or any individual paediatric neurologists.
Thirdly we are unable to accept that unless there is documented fetal
acidaemia that intrapartum hypoxia can be excluded as the cause of
cerebral palsy in any individual case. Certainly retrospectively and also
frequently in current practice reliable measures of fetal acidosis have
just not been sought. Under these circumstances it cannot be concluded
that the absence of documented fetal acidosis excludes the likelihood that
it occurred.
Fourthly we are disappointed that the statement was dismissive of the
role of neuro-imaging and electroencephalography. We believe that the use
both prospectively and retrospectively of brain imaging and EEG is of
particular value when attempting to time when brain insults have occurred,
especially when these data are used together with other information.
Fifthly we are surprised that no consideration whatsoever has been
given in the consensus statement to the patterns and timing of brain
injuries seen in infants born prior to 34-36 weeks of gestation. There is
a significant prevalence of cerebral palsy among prematurely born infants
and surely consideration of the causes should have been included as part
of the remit of any international taskforce.
Further whilst this document undoubtedly represents consensus reached
after extensive discussion amongst those selected to participate, in no
way does it contain a meta-analysis of the kind usually required before an
authoritative guideline can be produced.
Finally we have to admit to surprise that the section on expert
witnesses should have been allowed to remain in a peer reviewed journal
published in Britain.
Quite clearly neither the authors of the articles nor the reviewers
nor the editors for the British Medical Journal can be aware of recent
changes within English law subsequent to the Woolf recommendations and
reforms that have now been instituted. These define and explain the role
of the expert witness far more objectively than has MacLennan.
Yours faithfully,
L Rosenbloom,
Consultant Paediatric Neurologist, Alder Hey Children’s Hospital, Eaton
Rd, Liverpool L12 2AP
J M Rennie
Consultant in Neonatal Medicine, King’s College Hospital, Denmark Hill,
London SE5 9RS.
Reference List
1. MacLennan A. A template for defining a causal relation between
acute intrapartum events and cerebral palsy: international consensus
statement. BMJ 1999;319:1054-9.
2. Bakketeig, L. S. Only a minor part of cerebral palsy cases begin
in labour. BMJ 319, 1016-1017. 1999.
Ref Type: Journal (Full)
Competing interests: No competing interests
The thesis set out by Dr Little 1862 1 that cerebral palsy (CP) was
primarily due to perinatal cerebral injury did not meet with approval from
the London Obstetrical Society – an obvious conflict of interests. One
might have hoped that 137 years later a reasonably balanced view on the
role of intrapartum asphyxia in causing brain injury would have become
established but it is clear from the recent consensus statement from a
group calling themselves the International Cerebral Palsy Task Force 2
that the latter day echoes of those opposing voices still resonate. In
setting out a template for establishing the probable cause of cerebral
palsy this statement does make some useful points but there are some
aspects which most certainly require further debate.
The first is the need to recognise that in most cases where it is
possible to form a view on what caused CP this can only be done in
probabilistic terms. The question then is how much certainty is enough?
In a clinical context this will vary according to the circumstances but in
the medico-legal context the answer is clear - it is “more than 50%
certainty” (i.e. p <0.5).
In the medico-legal context the facts that intrapartum asphyxia
rarely causes CP and that CP is rarely due to intrapartum asphyxia are
irrelevant, as long as it is accepted that CP is sometimes caused by
intrapartum asphyxia. In that case, when confronted with a case of CP
which could be due to intrapartum asphyxia and in which there is evidence
of intrapartum asphyxia of potentially damaging severity, the relevant
question to ask is “are these events probably causally-related or are they
probably coincidental”? The answer is that they are more likely to be
causally related, as long as no better explanation for the CP is
forthcoming. This flows from basic probability theory dealing with
conditional probabilities. That is, the probability of events A and B
both occurring is the probability of “A” multiplied by the
probability of “B given A”. As long as event B is more likely to occur if
event A has occurred, when A and B both occur they are
more likely to be causally related than to be independent chance
occurrences.
The second point we wish to make concerns the insistence in the
consensus statement on the demonstration of a certain severity of
metabolic acidaemia in arterial blood, obtained from the umbilical cord or
the baby within an hour of birth, before considering attributing CP to
intrapartum asphyxia. We agree that this is strong evidence which it
might be necessary to have in order to form a view which approaches
certainty (e.g. p <0.05). It is not essential information for forming
a view on causation “on the balance of probabilities”. For instance, if a
baby is born by emergency caesarian section following placental abruption,
requires a lot of resuscitation at birth, suffers from an acute neonatal
encephalopathy and acute renal failure and then develops athetoid cerebral
palsy with MRI scan evidence of basal ganglia injury, then it certainly is
possible to say that acute intrapartum asphyxia is the probable cause of
disability regardless of whether or not metabolic acidaemia was
demonstrated.
This insistence on the demonstration of metabolic acidaemia is flawed
for a number of reasons, as follows:
1. Cord blood gas analysis is not universally practiced.
2. If a baby needs a lot of resuscitation and stabilization, an hour
can easily slip by before arterial blood is analysed for pH
3. Often cord venous blood is obtained and a venous pH above 7.0 or
base deficit of less than 12 mmol/L is not inconsistent with damaging
intrapartum asphyxia as a result of cord compression.
4. Sodium bicarbonate is often used as part of resuscitation and
blood from the baby after resuscitation will not reflect the acid-base
status at birth.
5. If the Task Force recommendations were to be accepted the best
defensive approach to possible litigation would be to ensure that no
assessment of acid-base status around birth is made. Then, according to
the Task Force, an intrapartum cause for cerebral palsy cannot begin to be
considered.
References
1. Little WJ. On the influence of abnormal parturition, difficult
labours, premature birth and asphyxia neonatorum on the mental and
physical condition of the child, especially in relation to deformities.
Trans Obstet Soc Lond 1862;3:293-344.
2. Alastair MacLennan for the International Cerebral Palsy Task
Force. A Template for defining a causal relation between acute
intrapartum events and cerebral palsy: international consensus statement.
BMJ 1999;319:1054-59
Competing interests: No competing interests
cerebral palsy is a good issue to audit our knowledge
Editor,
we believe these statements are interesting and that they will rise a
fair debate in several countries. They are particularly stimulating,
especially for places, like Italy, where practitioners tend to justify with
fear of litigation the rising number of obstetrical interventions and on
the other hand there is a major pressure for natural childbirth from the
public.
Finally "expert opinion" for malpractice litigations is taking a
significant part of the time of peer obstetricians, a time that would be
best employed in teaching and clinical practice. Every country has its own
legal system which obviously influences the attitude of lawyers and peer
reviewers. Therefore it is going to be difficult to have common guide-
lines for this topic. Still we strongly support the idea that the
international scientific community should both produce these statements
and encourage national colleges and societies to divert money and
expertise into this direction. As a national society we are supporting a
prospective survey of cerebral palsy. We believe that common criteria of
defintion of the medical events and share of information between experts
are the key to face this murky matter.
Pantaleo Greco
Antonella Vimercati
Luigi Selvaggi
for the Italian Society of Perinatal Medicine
Competing interests: No competing interests