Aust N Z J Obstet Gynaecol 1997 p1

7/27/2019 Aust N Z J Obstet Gynaecol 1997 p1

1/5

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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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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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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