3Eisenberg JM. Globalize the evidence, localize the decision: evidence-
based medicine and international diversity. Health Aff 2002;21:166-8.
Clarke M, Chalmers I. Discussion sections in reports of controlled trials
published in general medical journals: islands in search of continents?
Global Programme on Evidence for Health Policy. Guidelines for WHO
guidelines (EIP/GPE/EQC/2003.1.). Geneva: WHO, 2003 (www.who.int/
GRADE Working Group. Grading quality of evidence and strength of
recommendations. BMJ 2004;328:1490.
Kim Y, Hahn S, Garner P. Reduced osmolarity oral rehydration solution
for treating dehydration caused by acute diarrhoea in children. Cochrane
Database Syst Rev 2001(2):CD002847. Update in: Cochrane Database Syst
Child and Adolescent Health Development,WHO.Oral rehydration salts
(ORS): a new reduced osmolarity formulation. www.who.int/child-
28 Jul 2004).
Olliaro P, Mussano P. Amodiaquine for treating malaria. Cochrane
Database Syst Rev 2003(2):CD000016.
10 McIntosh HM, Olliaro P. Artemisinin derivatives for treating uncompli-
cated malaria. Cochrane Database Syst Rev 2000(2):CD000256.
11 Smith H. Better Births Initiative in South Africa. British Journal of
12 Thomson O’Brien MA,Oxman AD,Haynes RB,Davis DA,Freemantle N,
Harvey EL. Local opinion leaders: effects on professional practice and
health care outcomes. Cochrane Database Syst Rev 2000(2):CD000125.
13 Smith H, Brown H, Hofmeyr GJ, Garner P. Evidence-based obstetric care
in South Africa—influencing practice through the ‘Better Births
Initiative.’ S Afr Med J 2004;94:117-20.
14 Jamtvedt G, Young JM, Kristoffersen DT, Thomson O’Brien MA, Oxman
AD. Audit and feedback: effects on professional practice and health care
outcomes. Cochrane Database Syst Rev 2003(3):CD000259.
15 Plsek P,Wilson T.Complexity,leadership,and management in healthcare
organisations. BMJ 2001;323:746-9.
16 Grol R, Grimshaw J. From best evidence to best practice: effective imple-
mentation of change in patient care. Lancet 2003;362:1225-30.
17 Harvey G, Wensing M. Methods for evaluation of small scale quality
improvement projects. Qual Saf Health Care 2003;12:210-4.
Inappropriate use of randomised trials to evaluate
complex phenomena: case study of vaginal breech
As randomised trials continue to ascend in the evolution of evidence based medicine, we must
recognise and respect their limitations when examining complex phenomena in heterogeneous
Randomised controlled trials have greatly improved
the quality of evidence guiding clinical practice, but
when applied to complex phenomena, they have
important limitations. Complex patient populations
with poorly quantifiable variations between individuals
present one area of difficulty; complex procedures
requiring skill and clinical judgment present another.
A large, well designed, and well executed randomised
controlled trial of breech presentation at term, the
“term breech trial,” by Hannah et al rapidly dictated a
new standard of care for the management of breech
deliveries around the world.1Yet this trial failed to
adequately appreciate both the complex nature of
vaginal breech delivery and the complex mix of opera-
tor variables necessary for its safe conduct.Widespread
acceptance of this trial’s results has breached the limits
of evidence based medicine.
Hannah et al’s trial showed a significant increase in
perinatal mortality and morbidity in women ran-
domised to a trial of labour compared with elective
caesarean section.1The trial’s methodological flaws
have been examined,2–4but the intrinsic limitations of
phenomena have received little attention. These
limitations are the focus of this paper.
Bias of licence
Many of the term breech trial’s 121 centres were in
North America, where 13% of breech presentations at
term were delivered vaginally.5The study achieved a
successful vaginal delivery rate of 57% by asking those
centres with vaginal birth rates under 40% in the
labour group to increase the rate or withdraw from
Individual centres rates of vaginal
breech delivery at baseline were not reported, but
many would have tripled their vaginal delivery rate
The vaginal delivery of a breech baby involves risk.
Cord prolapse and trapped fetal parts are unpredict-
Vaginal breech delivery is a complex procedure
MOTHER AND BABY PICTURE LIBRARY
Education and debate
University of British
V6H 3V5 Canada
BMJ VOLUME 32930 OCTOBER 2004bmj.com
able complications. Every practitioner knows this; and
the literature, the courts, and the low baseline rate of
such deliveries in North America highlight caution.
Maternity units with interest and skill in delivering
breech babies vaginally have achieved higher rates:
24% in the United States, 36% in Sweden, 38% in
Israel, 38% in Switzerland, 39% in France, and 53% in
selected women for a trial of labour using various
safety criteria and showed lower mortality and morbid-
ity associated with vaginal breech delivery than in the
term breech trial. Few obstetrical units other than Løv-
set’s have published vaginal delivery rates as high as the
term breech trial.12
Statistical power required a high vaginal delivery
rate to enhance the trial’s ability to detect small differ-
ences in outcome. With this aim, the researchers
encouraged practitioners to increase their vaginal
breech delivery rate beyond their previous comfort
level. Despite being difficult to quantify, comfort level
(or “practitioner comfort level”) plays a pivotal part in
the safety of complex procedures. Protected from
medicolegal liability by the equipoise of a randomised
trial, some practitioners must have pushed their
comfort levels with vaginal breech delivery. This
constitutes a significant bias: one of licence. The trial
protocol’s liberal labour guidelines allowed 0.5 cm
dilation/h and 3.5 hours for the second stage. This is
considerable licence, and few obstetricians from
centres with proved safety in vaginal breech delivery
would find them acceptable.
A discriminating procedure
Human skill varies. This is particularly evident when
tasks are complex, require careful judgment, and have
narrow margins for error. Increasingly complex tasks
are discriminating, with more effort and skill required
to master them. The safe vaginal delivery of a breech
baby requires considerable skill and is a discriminating
obstetrical procedure. Skill is required in multiple are-
nas: not just in the delivery technique, but in
ultrasound assessment, the selection of cases, intra-
partum fetal surveillance, the conduct of labour, and
paediatric support. A coordinated, well functioning
unit is difficult to quantify.
include carotid endarterectomy, where surgical skill is
one of the strongest predictors of the operation’s
utility;13 14surgery for cancer, where additional surgical
training improves outcome;15 16and vaginal hysterec-
tomy. Rates of vaginal hysterectomy vary greatly
among surgeons, and the learning curve to increase an
individual surgeon’s rate takes years.17It has been sug-
gested that “encouraging more surgeons to perform
more vaginal hysterectomies may result initially in an
increasing complication rate because it is technically
In the United Kingdom and in North America, the
baseline vaginal hysterectomy rate for non-malignant
disease is 20%. Encouraging a group of surgeons to
suddenly increase their rate from 20% to 60% would
not be a meaningful way to evaluate the safety of the
procedure compared with abdominal hysterectomy.
Nor should all women have an abdominal hysterec-
tomy because some are poor candidates for vaginal
surgery and because some surgeons lack the skill or
experience to support a safe, high vaginal hysterec-
tomy rate. Case selection depends on diagnosis, parity,
size and mobility of the uterus, and operator skill,
which together determine a safe baseline rate. Increas-
ing the rate arbitrarily and randomising such a
complex mix of patient and operator characteristics
would compromise safety, yet this is what happened in
the term breech trial.
Homogenising populations and
Randomisation improves the internal validity of trials
by homogenising study and control populations
thereby avoiding bias from differences between the
two. Clinically important factors that are variable
within populations are, however, homogenised as well.
Their importance to the outcome is lost, and the trial
loses external validity for individuals within subsets of
the population. Results represent the mean outcome
for all participants and are not applicable to subgroups
at lower risk. Although subgroup analysis, found in the
term breech trial, can potentially identify subpopula-
tions in which a procedure may be safer,it is statistically
weak. When phenomena are complex, many patient
and practitioner characteristics influence outcome,
rendering individual subgroups small and meaningful
analysis of them difficult.
A major limit of evidence based medicine is the dif-
ficulty in applying the results of randomised trials to
individual patients.For example,most would agree that
a multiparous woman in advanced labour at 38 weeks
with a 3000 g fetus in a frank breech presentation with
flexed head and no nuchal cord represents a low risk
subgroup of all breech presentations. By studying a
heterogeneous group of women, the term breech trial
lacks the external validity needed to guide us with the
caesarean, not trusting their clinical judgment to
discern low risk situations, because all women with a
breech presentation have been assigned a similar risk
status by a randomised controlled trial.
Multicentre trials can also lead to homogenisation
of the intervention. Previous randomised trials of
breech presentations were too small to detect clinically
multicentre trial was required to improve statistical
power. Yet despite the interest, altruism, and self refer-
ential experience of the practitioners, the involvement
of 121 centres resulted in an average level of care.
Encouraging practitioners to exceed their comfort
level with vaginal breech delivery lowered that
If generic levels of care had always been accepted as
the ideal, none of the surgical subspecialties would
have arisen. The standard of care shown by the term
breech trial is not the best we can offer. Although
breech deliveries commonly occur under average con-
ditions, it does not mean that committed centres are
unable to offer better than average care.Collectively we
have been improving our “mean”level of care for years,
and the perinatal risk associated with breech delivery
has continued to drop despite stabilisation of the
caesarean section rate.19
Education and debate
BMJ VOLUME 32930 OCTOBER 2004bmj.com
Simplified risk reduction
Historically,the greatest decrease in perinatal mortality
from vaginal breech deliveries was reported by Bracht
in 1938.20Other techniques recommended to enhance
the safety of vaginal breech delivery include routine
determination of fetal weight, head attitude, and
nuchal or presenting cord using ultrasonography;con-
tinuous fetal monitoring; radiological pelvimetry; cau-
tious attention to the progress of labour; and
preparing for emergency symphysiotomy should fetal
parts become trapped.21Although poorly amenable to
scientific analysis, some of these techniques are likely
to be important for safe vaginal breech delivery. None
were included in the term breech trial.
It is impractical for a large, multicentre trial to use
complex risk reducing strategies. Meaningful quality
control in 121 centres is impossible, and more caution
would have meant fewer vaginal deliveries, increasing
the number of participants needed to achieve similar
statistical power. Therefore, the researchers chose a
simple labour protocol with few risk avoidance
strategies. The lack of proved effectiveness of other
strategies ostensibly justified their exclusion; yet our
current inability to analyse safe vaginal breech delivery
does not preclude its existence. The resulting standard
of care, arguably reasonable for a large, multicentre
trial, falls short of its designation as the definitive study
of vaginal breech delivery.
Since publication of the term breech trial,the onus
has been placed on individual obstetrical units to ret-
rospectively examine their experience with vaginal
breech delivery and to show safety. Several have done
so and continue to offer vaginal breech delivery.11 22 23
Safety in these specific centres is due to heterogeneity
of human skill, not to statistical anomaly, and vaginal
breech delivery in those units should be studied and
emulated. For complex phenomena, a large, ran-
domised, multicentre trial does not overrule demon-
In the case of carotid endarterectomy,it should ide-
ally be performed at a centre and by a surgeon with a
perioperative stroke rate of 3%, not 6%. If unavailable,
a patient might elect medical treatment, as the risks
could outweigh the benefits. Similarly, a woman with
an average breech presentation and access to average
care may decide that a caesarean section is safer than a
trial of labour; yet even that conclusion is potentially
flawed: without a bias of licence, the maternity unit car-
ing for her may well have a low, safe, baseline vaginal
breech delivery rate.
Short term combined end points
Randomised trials often utilise short term end points
because they are easier to measure than longer term
outcomes. It is also easier to show a statistical
difference in a combined end point rather than a sin-
gle end point. Yet combined end points can be
misleading.24In the term breech trial, the end point
included perinatal mortality and various short term
morbidities, including hypotonia, transient brachial
plexus injury, and isolated low arterial cord pH or
base excess, whose lasting significance is unclear. In
countries with low perinatal mortality, this combined
end point occurred in 5.7% of planned vaginal
deliveries and 0.4% of women undergoing elective
caesareans. Mortality was not significantly different
(3 of 511 or 0.6%) in the planned vaginal delivery
group compared with zero in the planned caesarean
group. One of these deaths, included in the intention
to treat analysis,occurred before the onset of labour in
a cephalictwin weighing
concerns about the adequacy of case selection and
intention to treat analysis at all cost. Regardless, the
impact of the trial’s results was due primarily to an
excess of short term morbidity in the planned vaginal
Long term outcomes in breech babies are hard to
assess epidemiologically, but were retrospectively
shown to be equivalent in 1645 children, irrespective
of the planned mode of delivery.25
from the term breech trial have published details on
death or abnormal neurodevelopment over two years
in a subgroup of 923 children from the term breech
trial.26They found a similar incidence: 2.8% in the
planned vaginal delivery group and 3.1% in the
elective caesarean section group. The use of a short
term combined end point seems to have been
1150 g, highlighting
The limits of evidence based medicine
Delivering a breech presentation vaginally is a skill:
guided by science, its safety relies on the experience of
practitioners and caution. In the term breech trial,
large scale randomisation, which homogenised both
the study populationand
resulted in an average level of care in an average
population, limiting the trial’s external validity in cen-
tres showing above average skill and in women of
below average risk. Encouraging practitioners to
exceed their comfort level ensured a high vaginal
delivery rate and adequate statistical power, but intro-
duced a bias of licence and compromised safety. Using
a combined short term end point overstated any true
effect on long term neurodevelopment.
medicine include failing to appreciate and cultivate the
complex nature of sound clinical judgment, failing to
When applied to complex phenomena,
randomised trials have important limitations
Vaginal breech delivery is a complex procedure
that is poorly amenable to the methods of large
multicentre randomised trials
One randomised controlled trial has dictated a
new standard of care for vaginal breech deliveries
The use of a short term combined end point
overstated any true risk of planned vaginal
delivery to longer term neurodevelopmental
Education and debate
BMJ VOLUME 32930 OCTOBER 2004bmj.com
appreciate the relevance of poorly quantifiable clinical
phenomena that are obscured by randomisation, and
devaluing the intangible differences between individu-
als, thus potentially devaluing them (patients and care
providers).27The condemnation of vaginal breech
delivery by one randomised controlled trial and its
sweeping effect on clinical practice show how each of
these philosophical limits can be exceeded.
The author thanks Ewart Woolley, whose skill in vaginal breech
deliveries inspired him, and Robert Liston and Michael Klein
for their support and direction.
Competing interests: None declared.
Ethical approval: Not required.
1Hannah ME, Hannah WJ, Hewson SA, Hodnett ED, Saigal S, Willan AR.
Planned cesarean section versus planned vaginal birth for breech
presentation at term: a randomised multicentre trial. Term Breech Trial
Collaborative Group. Lancet 2000;356:1375-83.
Hauth JC,Cunningham FG.Vaginal breech delivery is still justified.Obstet
Keirse MJ. Evidence-based childbirth only for breech babies? Birth
Halmesmaki E. Vaginal term breech delivery—a time for reappraisal?
Acta Obstet Gynecol Scand 2001;80:187-90.
Lee KS, Khoshnood B, Sriram S, Hsieh HL, Singh J, Mittendorf R. Rela-
tionship of cesarean delivery to lower birth weight-specific neonatal mor-
tality in singleton breech infants in the United States. Obstet Gynecol
University of Toronto Maternal, Infant and Reproductive Health
Research Unit. Term breech trial study protocol, 1996:8.
Sanchez-Ramos L, Wells TL, Adair CD, Arcelin G, Kaunitz AM, Wells DS.
Route of breech delivery and maternal and neonatal outcomes. Int J
Gynecol Obstet 2001;73:7-14.
Lindqvist A, Lindeberg SN, Hanson U. Perinatal mortality and route of
delivery in term breech presentations. Br J Obstet Gynaecol 1997;
Schiff E, Friedman SA, Mashiach S, Hart O, Barkai G, Sibai BM. Maternal
and neonatal outcome of 846 term singleton breech deliveries:
seven-year experience at a single center. Am J Obstet Gynecol 1996;175:
10 Irion O, Almagbaly PH, Morabia A. Planned vaginal delivery versus elec-
tive cesarean section: a study of singleton term breech presentations. Br J
Obstet Gynaecol 1998;105:710-7.
11 Kayem G, Goffinet F, Clement D, Hessabi M, Cabrol D. Breech presenta-
tion at term: morbidity and mortality according to the type of delivery at
Port Royal Maternity hospital from 1993 through 1999. Eur J Obstet
Gynecol Reprod Biol 2002;102:137-42.
12 Albrechtsen S, Rasmussen S, Reigstad H, Markestad T, Irgens LM,
Dalaker K. Evaluation of a protocol for selecting fetuses in breech
presentation for vaginal delivery or cesarean section. Am J Obstet Gynecol
13 Tu JV, Hannan EL, Anderson GM, Iron K, Wu K, Vranizan K, et al. The
fall and rise of carotid endarterectomy in the United States and Canada.
N Engl J Med 1998;339:1441-7.
14 Barnett HJ, Taylor DW, Eliasziw M, Fox AJ, Ferguson GG, Haynes RB, et
al. Benefit of carotid endarterectomy in patients with symptomatic mod-
erate or severe stenosis.North American Symptomatic Carotid Endarter-
ectomy Trial Collaborators. N Engl J Med 1998;339:1415-25.
15 Mayer AR, Chambers SK, Graves E, Holm C, Tseng PC, Nelson BE, et al.
Ovarian cancer staging: does it require a gynecologic oncologist. Gynecol
16 Tingulstad S, Skjeldestad F, Hagen B. The effect of centralization of pri-
mary surgery on survival in ovarian cancer patients. Obstet Gynecol
17 Varma R,Tahseen S,Lokugamage A,Kunde D.Vaginal route as the norm
when planning hysterectomy for benign conditions: change in practice.
Obstet Gynecol 2001;97:613-6.
18 Maresh M, Metcalfe M, McPherson K, Overton C, Hall V, Hargreaves J, et
al. The VALUE national hysterectomy study: description of the patients
and their surgery. Br J Obstet Gynaecol 2002;109:302-12.
19 Albrechtsen S, Rasmussen S, Irgens LM. Secular trends in peri- and neo-
natal mortality in breech presentation; Norway 1967-1994. Acta Obstet
Gynecol Scand 2000;79:508-12.
20 Bracht E. Zur Behandlung der Steisslage. Zentralblatt Gynaecol 1938;
21 Menticoglou SM. Symphysiotomy for the trapped aftercoming parts of
the breech:a review of the literature and a plea for its use.Aust NZ J Obstet
22 Giuliani A, Schoell W, Basver A, Tamussino K. Mode of delivery and out-
come of 699 term singleton breech deliveries at a single center. Am J
Obstet Gynecol 2002;187:1694-8.
23 Alarab M, Regan C, O’Connell MP, Keane DP, O’Herlihy C, Foley ME.
Singleton vaginal breech delivery at term: still a safe option. Obstet Gyne-
24 Julian D. What is right and what is wrong about evidence-based
medicine? J Cardiovasc Electrophysiol 2003:14(Suppl);S2-5.
25 Danielian P, Wang J, Hall M. Long term outcome by method of delivery
of fetuses in breech presentation at term: population based follow up.
term breech trial.Am J Obstet Gynecol 2003;Suppl 189(6).[Abstract No 7.]
27 Tonelli MR. The philosophical limits of evidence-based medicine. Acad
(Accepted 5 October 2004)
Effect of postnatal depression on other members of the mother’s family
Does anyone know of any journals or sites with information on
how postnatal depression affects the rest of the family, not just the
Oliver Mallon, student nurse,Queens University,Belfast
Different effects appear at different stages of child development.
The leading figure in UK research in Professor Lynn Murray. She
has been publishing in the area of effects of postnatal depression
on child development for about 15 years. Here are details of three
of her characteristic studies.
Murray L. The impact of postnatal depression on infant
development. J Child Psychol Psychiatry 1992;33:543-61.
Infants of postnatally depressed mothers performed worse on
object concept tasks, were more insecurely attached to their
mothers, and showed more mild behavioural difficulties. Postnatal
depression had no effect on general cognitive and language
development, but seemed to make infants more vulnerable to
adverse effects of lower social class and male sex.
Murray L, Woolgar M, Cooper P, Hipwell A. Cognitive
vulnerability to depression in 5-year-old children of depressed
mothers. J Child Psychol Psychiatry 2001;42:891-9.
In a situation of mild stress (the threat of losing a deal in a
competitive children’s card game), 5 year old children of
depressed mothers were more likely to express depressive
cognitions (hopelessness, pessimism, and low self worth) than
children of well mothers. The association between depressive
cognitions and recent exposure to maternal depression was in
part accounted for by current maternal hostility to the child.
Sinclair D, Murray L. Effects of postnatal depression on children’s
adjustment to school. Teacher’s reports. Br J Psychiatry 1998;172:
Family social class and the child’s sex had the greatest influences
on 5 year old children’s behavioural adjustment. However, both
postnatal and recent maternal depression were associated with
significantly raised levels of child disturbance, particularly among
boys and those from lower social class families.
Woody Caan, professor of public health,APU,Chelmsford
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