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Aust.
z
Obstet Gynaecol
997;
37:
1: 1
THE AUSTRALIAN
&
NEW
ZEALAND
JOURNAL
OF
OBSTETRICS
GYNAECOLOGY
February
1997
VOl. 37 No.
OCCASIONALREVIEW
From Delivery Suite
to
Laboratory:
Optimizing Returns
from
Placental Examinationin
Medico-legalDefence
T.Y. Khong
Department of Pathology Womens
and
Childrens Hospital North Adelaide South Australia
Summary:
While examinations of the placenta may reveal significant lesions that are
helpful in a medico-legal context, its value may
be
diminished by a lack of attention
to detail in the period between delivery of the baby and receipt of the placenta in the
pathology department. These fall generally into
2
groups: initial description and
handling of the placenta and lack of relevant clinical information. This
communication describes some of these pitfalls. By observing these details, the onus
then falls on the pathologist to provide a meaningful assessment of the placenta.
The average Australian obstetrician might be
expected to be involved in obstetric litigation once in
10 to
15
years. The common reasons for litigation are
fetal death in utero, fetal distress and alleged cerebral
hypoxia resulting from obstetric management.
Placental examination may be important in perhaps
25
of obstetric cases that are litigated. Most cases in
which the placenta has been available conclude in the
favour of the defending obstetricians and hospitals
(1).An insurance company review found that verdicts
were in favour of the defence in all 12 neurologically
impaired infant claims tried to a conclusion when the
placenta and/or cord was available for examination
(2). It is estimated that 15 of all pregnancies have
abnormalities hat can be explained by an experienced
pathologist who has examined the placenta (3).
Nevertheless, failure to pay attention to detail in the
period
between delivery of the baby and receipt of the
Address
for
correspondence:
DrT.Y. Khong,
Placenta Research Unit
Department
of
Histopathofogy
Adelaide Womens and Childrens Hospital
North
Adelaide
South
Australia
5006,
Australia.
placenta by the pathology department can negate the
value of placental examination and it5 place in
risk
management. This aspect appears to be neglected
or
overlooked although there have been several recent
texts and articles detailing the pathology of the
placenta and of the significance of placental
examination in the medico-legal context
4-7).
The
purpose of this review is to highlight some of these
pitfalls and to note practicalaspectsof the initial
gross
placental examination and its submission to the
pathology department that will ensure that the
placental pathology report will be meaningful.
Examination
of
placentas: triage
It is a truism that no information can be gleaned if
the pZacenta is not examined. While some advocate
examination of all placentas by a pathologist
(6)
most
pathology departments realistically agree that a triage
of placentas is necessary so as not to overwhelm the
diagnostic pathology service. Which placentas should
be sent for pathological examination will depend, to
an extent, on the interests of the local obstetrics and
pathology departments but guidelines
re
available
for indications for placental examination 3,8). It is a
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2
AUST.AND N.2. JOURNAL OF OBSTETF3CS
AND GYNAE COL oGY
good idea to incorporate a system where those
placentas that are not sent for pathological examin-
ation can
be
stored in a refrigerator for about
I
week
so
that the placenta of the seemingly healthy infant
who experiences early postnatal problems can be
retrieved for examination (4,8,9).
Maternal indications for pathological examination
include diabetes mellitus, preeclampsia, premature
rupture of membranes, prolonged rupture of mem-
branes, preterm delivery,
placenta praevia, post-
maturity and poor previous obstetrical history. Fetal
indications include stillbirth, neonatal death, multiple
gestation, prematurity, intrauterinegrowth retardation,
congenital anomalies, hydrops, meconium-stained
liquor, low Apgar scores, admission to a neonatal
intensive care unit, abnormal fetal cardiotocography
and suspected infection.
Handling of placentas n delivery suit
Each placenta should be examined promptly after
delivery in the delivery suite, allowing findings of
immediate importance to be detected and acted upon
clinically.
It also allows placentas that otherwise
would not have been sent for pathological examin-
ation for maternal or fetal indications to be identified
for submission for pathological examination for
placental reasons. Placental indications are placental
abruption, infarcts, placenta praevia, abnormal
calcification and any abnormal appearance of placenta
and/or cord and/or membranes.
Missing cotyledons or membranes could highlight
the possibility of retained placental fragments that
could give rise to postpartum haemorrhage, failure of
uterine contraction and involution or endometrial
infection. Some placentas, however, have a disrupted
maternal surface rendering accurate assessment of
completeness impossible. The pathologist should be
alerted to any tissue taken for research, although such
tissue usually has a sharp cut edge,
so
that an
erroneous report of incomplete placenta is not
generated. Ruptured fetal vessels, such as ruptured
vasa praevia or necrosis
of
umbilical arteries, should
alert the neonatologist to the possibility
of
needing
neonatal transfusion. In the latter case, additional
neonatal problems, such
as
intestinal atresia, may be
suggested (10.1 1). Opaque membranes or malodorous
placenta would suggest acute chorioamnionitis and
neonatal infection.
Other observations routinely performed include
weighmg of the placenta and checking for the number
of umbilical cord vessels. Recording of the placental
weight fell into disrepute when it was shown that the
placental weight is subject to great variation and
inaccuracies (12). There is no standard routine for
weighing the placenta and the inaccuracies may derive
from inclusion or exclusion of the membranes,
umbilical cord n its entirety or in part, maternal
blood entrapped in the intervillous space, fetal blood
trapped in the placenta subject to timing or cord
clamping and the use of oxytocics and, sometimes,
amniotic liquor. Notwithstanding these criticisms, the
recent epidemiological findings of Barker and his
colleagues relating intrauterine events to adult disease
1
3) justifies continued weighing of the placenta and
attempts to standardize the technique. Furthermore,
placental weights below the 10th percentile or above
the 90th percentile should alert the examiner to
pos-
sible maternal and fetal disorders.
The dimensions of the placenta are often measured
in the delivery suite. Apart from the extensive placenta
membranacea, no relation between placental dimen-
sions and perinatal outcome has been demonstrated
and the routine should be desisted. The placenta
membranacea is defined as an abnormally diffuse
placenta covering all,
or
most, of the membranes and
is associated with recurrent antepartum bleeding,
premature onset of labour, postpartum haemorrhage
and morbid adherence of the placenta (14). The length
of the umbilical cord is often measured. An unusually
long cord, defined as greater than 100 cm, leaves it
susceptible to cord prolapse and venous thrombosis
while a short cord, defined
as
less than 32 cm, may
restrict fetal descent and result in placental separation,
fetal distress or cord rupture. It is obvious that these
measurements are best done in the delivery suite since
the midwife or accoucheur will know how much of
the cord is left on the baby or if additional segments
had been taken for blood gas measurements or for
research, etc
(9);
the pathologist is in no position to
defend allegations
of
fetal distress due to short cords
if he is unsure
if
the cord received in the laboratory
was the entire length. In this regard, it is also helpful
for the accoucheur to record the location of the
placenta in utero since the placental location and
umbilical cord insertion must be considered when
studying short cords
1 5 . A
note should
be
made of
the site of umbilical cord insertion since velamentous
cord insertions could
be
associated with lacerations,
compression or thrombosis of vessels
(
16).
Manipulation of the placenta may be detrimental to
subsequent examination by a pathologist. Thus, in
trying
to
ascertain the lucency
of
the membranes,
wiping the membrane with the hand to promote better
visualization may inadvertently remove amnion
nodosum, which are nonadherent,
in
contrast to
amniotic squamous metaplasia which is less easily
removed. Similarly, loose andor adherent blood clot
may be removed in handling the maternal surface.
Unless these findings are recorded and communicated
to the pathologist, the possibility of a fresh retro-
placental haematoma or placental abruption may be
overlooked when the placenta is assessed histo-
logically since there may be only microscopic
evidence of acute changes in intervillous blood flow.
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T.Y. h O N G
3
With twin placentas, labelling of the umbilical cord
with 1 clamp for the first twin and 2 clamps for the
second twin eliminates any confusion that can arise if
a no clamp/l clamp labelling is used as it may not be
apparent if the 1 clamp in the no clamp/l clamp
system is for
the
first or the second twin.
This is
important because pregnancy and/or delivery compli-
cations may affect only 1 twin. Thus, for example,
meconium staining, acute chorioamnionitis or amnion
nodosum could be present or be more pronounced in
only 1 gestational sac; while correlation between
clinical outcome and pathology could be achieved
later, this is unsatisfactory and may not be possible.As
part of their clinical practice to attempt to inform
parents of the zygosity of multiple
births
midwives
often examine the chorionicity of the placenta in
multiple births by stripping the dividing membranes.
Unless
this
is done correctly and recorded accurately,
stripping of the dividing membranes may leave the
pathologist with a dog-ear of dividing membranes to
reconstitute and may render impossible any comment
of the chorionicity. This is important since perinatal
morbidity and mortality are dependent on chorionicity
and not on zygosity (17). A related issue in litigation
cases is whether the twins had twin-twin transfusion
syndrome. Establishing dichorionicity virtually mles
this out (18). Nevertheless, the preservation of an
adequate length of umbilical cord and leaving the
chorionic plate vessels intact allow unhampered
injection studies to be performed by the pathologist in
all cases of multiple pregnancies.
It should also be stated that stripping of the amnion
from the underlying chorion can make subsequent
swabbing of the subamniotic chorionic plate for
bacterial and fungal cultures more difficult. Further-
more, it may obliterate any evidence of a chordee
insertion of the umbilical cord wherein a fold of
amnion extends from the cord insertion site on the
surface for a distance proximally; this may
be
associated with limited cord movement and possible
circulatory compromise (16). Care should be taken in
examining the membranes
so
that
the
site of rupture is
not artifactually extended as that may obscure
assessment of its relation to the placental margin in
cases of placenta praevia.
The umbilical cord is often clamped with plastic
clips for stemming blood flow after delivery of the
baby. Unless umbilical cord haematomas are specifi-
cally looked for prior to cord clamping, it can be a
difficult diagnostic problem deciding if such a
haematoma is artifactual or had occurred spontan-
eously. Significant spontaneous cord haematomas are
associated with long cords and with cord prolapse and
can result in fetal exsanguination and fetal distress
(19).
Comments are sometimes made in delivery suite
notes regarding the finding of infarcts or excessive
fibrin deposition. These remarks, once annotated,
almost become anointed. It can be difficult to dis-
tinguish between massive perivillous fibrin deposition
and infarct
or
even a chorioangioma from an
examination of the maternal surface alone and the
credibility of the defence may be called into question
if the ultimate histological findings are at variance
with the initial
gross
placental examination. If these
findings need to be documented in the delivery notes,
it would be preferable to use descriptive t e r n such as
red, yellow or white plaques and to submit these
placentas for histological examination. Furthermore,
the extent of these lesions are important as are the
locations and these could be determined only after
examining slices of
the
cut placenta. The placenta can
withstand
20-30
villous loss through massive
perivillous fibrin deposition without any clinical ill-
effects but may be compromised by 510 villous
loss through infarction (12).
Before the placenta is despatched to the pathology
department, it is essential that it is labelled properly
and then sent fresh without any rinsing. Clinicians are
beseeched to send specimens in adequate volumes of
fixative (20) but the placenta is an example of an
exception to the rule. Receipt of the placenta
in
a
fresh
state permits
the pathologist to swab the
subamniotic space for evidence
of
amniotic fluid
infection or to take parenchymal samples for
biochemistry, virology and cytogenetics or to
perform
injection
studies of
the fetal-placental
vasculatum
in
multiple pregnancies.
Clinical
information
The omission of relevant clinical details in the
laboratory request form is not a monopoly of obstet-
ricians: many nurses and doctors commit this
misdemeanour
(2
1). The placenta is a rapidly evolving
organ in its approximate 40weeks life-span and its
responses to pathological processes
are
limited.
Unless the pathologist is provided with all relevant
information, interpretation of microscopic abnorm-
alities may be meaningless or, more worryingly,
misleading
(22).
The minimum clinical information
required include
the
gestational age, birth-weight and
the reason the placenta is submitted for examination.
A
very frequent omission is the gestational age of
the pregnancy at the time of delivery. Histological
comment on appropriateness of placental maturity is
often made and great reliance is placed on the gest-
ational age provided in the laboratory request form.
Villous immaturity may be seen in fetal anaemia due
to maternal-fetal rhesus isoimmunization or twin-twin
transfusion, maternal diabetes mellitus, anencephalus
and syphilis and is significantly infrequent in
preeclampsia 22).Accelerated villous maturation has
been described in preeclampsia and has been used as
a surrogate for uteroplacental vascular insufficiency
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4
AUST.ANV
N.Z.
JOURNALF OBSTETRICS
ND
GYNAECOLOGY
and defective placentation (23-25). Unless the
estimated date of delivery is provided, histological
assessment will be limited. The ideal request form
should provide the estimated dates of delivery from
both early pregnancy ultrasound and the last men-
strual period if they are discrepant.
Two other examples where clinical information
may be helpful are placenta praevia and morbid
adherence of the placenta. While placenta accreta
is
largely a clinical diagnosis, it would help the path-
ologist to be aware so that more blocks of the placenta
could be sampled to attempt to c o n f i i the diagnosis
on the placental histology when a hysterectomy has
not been performed (26,27). If the site
of
rupture in a
vaginal delivery is at the placental edge,
this
suggests
that the edge of the placenta may be encroaching on
the cervical
0s.
A site of rupture greater than
10
cm
from the placental edge is likely to follow a fundal
implantation.
Antenatal interventional procedures, such as cordo-
centesis and amniocentesis or intrauterine trans-
fusions, should be communicated to the pathologist
so
that complications such as funisitis can be sought
vigorously.
In
the case
of
cordocentesis, gross
evidence of the funicular puncture site can be readily
detected during the first month after the procedure but
may be inconspicuous after a month (28). Umbilical
cord haematomas may be associated with the
procedure (28) and need to be distinguished from
spontaneous or artifactual lesions.
The pathologist should also
be
informed about the
results of antenatal investigations. There are many
causes of elevated maternal serum alphafetoprotein
and placental examination may reveal unusual causes
unrelated to pregnancy complications (29,30).
Findings of positive serology for anticardiolipin
antibody or for lupus anticoagulant should prompt the
pathologist to sample the placenta extensively
or
to
modify the technique in order to assess the
uteroplacental vasculature
(31).
Obstetricians pathology colleagues
As stated earlier, it was not the intention of this
communication to review the various specific aspects
of placental abnormalities. Many placental abnorm-
alities are associated with perinatal morbidity and
mortality and with a poor short-term and long-term
outcome. However, all these abnormalities may also
be
associated with no untoward perinatal or maternal
sequelae. While it is important that the obstetrician,
and pathologist, recognize the limitations of placental
examination its potential utility should not be
compromised by a lack
of
detail
in
the interval
between delivery to receipt by the pathology depart-
ment. By strict adherence to detail and delivering the
placenta in an optimal state with all relevant clinical
information, the obstetricians can, and should,
demand a quality placental examination expertly
performed by their pathology colleagues: the onus of
providing a meaningful assessment
of
the placenta
shifts
to
the pathologist. It is then the pathologists
obligation to educate themselves about the placenta,
its morphology in health and disease and the relevance
of its morphological findings (32). Hopefully, the
numerous recent texts and publications, admittedly
largely in the domain of pathology (33-46), will have
raised the consciousness of the pathology community
to the placenta, hitherto a neglected organ.
cknowledgements
frequency
of
obstetric litigation.
I
thank
Dr
Hugh Aders for comments regarding
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