Prenatal diagnosis of congenital anomalies 3

Prenatal Diagnosis of
Congenital Anomalies
F.E.B.O.
G.

Background
 Ultrasound allows the detection of not
only major defects but also of soft
markers of chromosomal abnormalities .
 The vast majority of fetal abnormalities
occur in the low-risk group.
Consequently, ultrasound examination
should be offered routinely to all
pregnant women.

Background
 The Society of Obstetricians and
Gynaecologists of Canada (SOGC)
recommends a single “routine” ultrasound
evaluation at 16 to 20 weeks in all pregnancies.
 Patients need to be counselled about the
positive and negative findings that ultrasound
may reveal.

What is fetal anomaly?
 Definition:
"a marked deviation from the normal
standard, especially as a result of
congenital defects").
 An anomaly scan will not detect every
case of abnormality

The objective of the fetal anomaly scan is to reassure the
woman that her baby appears to have no obvious
structural abnormalities, and if this is not the case, to
identify anomalies:
 1. not compatible with life
 2. associated with high morbidity and long term disability
 3. fetal conditions with the potential for intrauterine
therapy
 4. fetal conditions that will require postnatal
investigations or treatments

Definition
 a soft marker is defined
as” ultrasound finding at
16-20 weeks gestation
which increases the risk
of the fetus having a
chromosomal anomaly”

The screening ultrasound at 16 to 20 weeks should evaluate 8
markers, 5 of which:-
1. Thickened nuchal fold
2. Echogenic bowel
3. Mild ventriculomegaly
4. Echogenic focus in the heart
5. Choroid plexus cyst
are associated with an increased risk of fetal aneuploidy, and
in some cases with nonchromosomal problems
while 3 (single umbilical artery, enlarged cisterna magna, and
pyelectasis) are only associated with an increased risk of
nonchromosomal abnormalities when seen in isolation
.
(II-2 B).

The minimum standard for a
"20 week" anomaly scan
 measurement of:-
 Bi-parietal diameter,
 head circumference
 femur length.
 abdominal circumference.
RCOG GUIDELINES

The minimum standard for a "20
week" anomaly scan
 Head shape + internal structures cavum pellucidum cerebellum
ventricular size at atrium (<10 mm)
 Spine: longitudinal and transverse
 Abdominal shape and content at level of stomach
 Abdominal shape and content at level of kidneys and umbilicus
 Renal pelvis (<5 mm AP measurement)
 Longitudinal axis - abdominal-thoracic appearance
(diaphragm/bladder)
 Thorax at level of 4 chamber cardiac view
 Arms - three bones and hand (not counting fingers)
 Legs - three bones and foot (not counting toes)
RCOG GUIDELINES

The optimal standard for the
"20 week" anomaly scan
The following could be
added to the features
above
Cardiac outflow tracts
Face and lips
RCOG GUIDELINES

Fetal Nuchal
Translucency
 Nuchal translucency refers to the normal
subcutaneous fluid-filled space between the back of
the fetal neck and the overlying skin.
 Sonographic criteria to maximize quality of nuchal
translucency sonography are:
1. Transabdominal or transvaginal approach should be
left to the sonographer's discretion, based on maternal
body habitus, gestational age, and fetal position.
2. Gestation should be limited to between 11 weeks 14
weeks.

3-Fetus should be examined in a midsagittal
plane.
4-Fetal neck should be in a neutral position.
5-Fetal image should occupy at least 75% of
the viewable screen.
6-Fetal movement should be awaited to
distinguish between amnion and overlying
fetal skin.
Fetal Nuchal
Translucency

 7-Calipers should be placed on
the inner borders of the nuchal
fold.
 8-Calipers should be placed
perpendicular to the long axis of
the fetal body.
 9-At least three nuchal
translucency measurements
should be obtained.
 10-At least 20 minutes might
need to be dedicated to the
nuchal translucency
measurement before
abandoning the effort
Correct
Incorrect
Fetal Nuchal
Translucency


Abnormal nuchal translucency .Normal nuchal
translucency

THICKENED NUCHAL
FOLD
Definition and Imaging Criteria
The nuchal fold is the skin thickness in the posterior aspect
of the fetal neck.
A nuchal fold measurement is obtained in a transverse
section of the fetal head at the level of the cavum septum
pellucidum and thalami, angled posteriorly to include the
cerebellum. The measurement is taken from the outer
edge of the occiput bone to the outer skin limit
* measurement of 6 mm is considered abnormal between
18 and 24 weeks

A thickened nuchal fold should be
distinguished from cystic hygroma, in
which the skin in this area has fluid-filled
loculations.
A thickened nuchal fold should not be
confused with nuchal translucency.
THICKENED NUCHAL
FOLD

THICKENED NUCHAL FOLD
Recommendations
1. A thickened nuchal fold significantly increases
the risk of fetal aneuploidy. by 17-fold, So
karyotyping should be offered . (II-1 A).
2. A thickened nuchal fold is associated with
congenital heart disease and may be an early
sign of hydrops. (II-2 B).
SOGC guidelines June 2005

 The integrity of the abdominal wall should
always be demonstrated; this can be
achieved by transverse scans demonstrating
the insertion of the umbilical cord. It is also
important to visualize the urinary bladder
within the fetal pelvis, because this rules out
exstrophy of the bladder and of the cloaca.
Anterior abdominal wall

Anterior abdominal wall
 Prevalence
 Exomphalos is found in about 1 per
4000 births.
 The majority of cases are sporadic
and the recurrence risk is 1%.
 However, there may be an associated
genetic syndrome. (mainly trisomy 18
or 13) in about 30% of cases.

 Diagnosis
 The diagnosis of exomphalos is based
on the demonstration of the mid-line
anterior abdominal wall defect, the
herniated sac with its visceral
contents and the umbilical cord
insertion at the apex of the sac.
Exomphalos

GASTROSCHISIS
 In gastroschisis, evisceration of the intestine
occurs through a small abdominal wall defect
located just lateral and usually to the right of
an intact umbilical cord. The loops of intestine
lie uncovered in the amniotic fluid.
 Prevalence
 Gastroschisis is found in about 1 per 4000
births.

BLADDER EXSTROPHY
AND CLOACAL
EXSTROPHY
 Bladder exstrophy is a defect of the
caudal fold of the anterior abdominal wall;
leads to exposure of the posterior bladder
wall.
 In cloacal exstrophy, both the urinary and
gastrointestinal tracts are involved.
 Cloacal exstrophy is the association of an
omphalocele, exstrophy of the bladder,
imperforated anus, and spinal defects
such as meningomyelocele.

 green arrows:
everted
bladder;
 blue arrows
the scrotum;
 yellow
arrows:
umbilcal
cord

HYDROPS FETALIS
 Definition:
 Hydrops is defined by abnormal
accumulation of serous fluid in skin
(edema) and body cavities (pericardial,
pleural, or ascitic effusions).
 Prevalence:
 Hydrops fetalis is found in about 1 per
2,000 births.

CARDIOVASCULAR
SYSTEM
Prevalence:
Cardiovascular abnormalities are found in
5-10 per 1,000 live births and in about
30 per 1,000 stillbirths
ASSESSMENT OF THE FETAL
heart
The heart can be observed in the four-
chamber, left and right chambers and
great vessel views.

CARDIOVASCULAR
SYSTEM
The four chambers view
The heart occupies one third of the thorax. The heart is
shifted to the left side of the chest, with the apex pointing
to the left. The axis of the interventricular septum is
about 45º to 20º to the left of the anteroposterior axis of
the fetus.
. The right ventricle is located behind the sternum and is
characterized by the presence of the moderator band.
Normally, both ventricles are approximately the same
size. The mitral valve insertion is slightly cephalad to the
insertion of the tricuspid valve). These features help
distinguish the right ventricle from the left ventricle).

 Evaluation of the cardiac outflow tracts can be difficult,
and at present it is not considered a part of the standard
examination of fetal anatomy.
 The outflow tracts and great arteries can be
demonstrated by slight angulations of the transducer
from the four-chamber view.
 By turning the transducer while keeping the left
ventricle and the aorta in the same plane, one can
obtain the left heart views,
 while the right heart views are obtained by moving the
transducer cranially and tilting slightly in the direction
of the left shoulder.
 The left heart views demonstrate the left ventricle and
aortic outflow tract.

VENTRICULAR SEPTAL
DEFECTS
 Are either isolated (about 50%) or
they are part of a complex heart
defect
Prevalence:
 Ventricular septal defects, which
represent 30% of all congenital
heart defects, are found in about
2 per 1,000 births.

VENTRICULAR SEPTAL
DEFECTS
 Diagnosis:
 depends on the
demonstration of a
dropout of echoes in the
ventricular septum.,
multiple views should be
used.

SINGLE UMBILICAL
ARTERY
Single umbilical artery (SUA) is the
absence of one of the arteries
surrounding the fetal bladder and in
the fetal umbilical cord.
 Assessment of the umbilical arteries
can be made from the cord itself and
on either side of the fetal bladder.
The assessment can be enhanced
with colour flow Doppler.

SINGLE UMBILICAL
ARTERY
Recommendations
1. The finding of a single umbilical artery
requires a more detailed review of fetal
anatomy, including kidneys and heart
Because it may be associated with both
underlying renal and cardiac abnormalities
. (II-2 B).
2. An isolated single umbilical artery does not
warrant invasive testing for fetal aneuploidy.
(II-2)

ECHOGENIC INTRACARDIAC FOCUS
Definition
Echogenic intracardiac focus (EICF) is defined
as a focus of echogenicity comparable to bone,
in the region of the papillary muscle in either or
both ventricles.
88% are only in the left ventricle, 5% are only in
the right, and 7% are biventricular.
Grade 2 suggests that echogenicity is equal to
bone, and grade 3 suggests it is greater

Prevalence:
 EIF are found in about 1.5% to 5.5% of
pregnancies
 Imaging Criteria
An EICF can be diagnosed on the standard 4-
chamber view of the fetal heart and should be
located within the ventricle where
papillary muscles are situated and
should move with valve leaflets (golf
balls); EIF should seen from more than
one angle .

ECHOGENIC
INTRACARDIAC FOCUS standard 4-chamber view

Recommendations
1. Isolated EICF require no further investigation when
maternal age or the serum screen equivalent is less than
the risk of a 31-year-old. (III-D).
2. Women with an isolated EICF and at increased
risk for fetal aneuploidy owing to maternal age
(31 years or more) or maternal serum screen
results should be offered counselling regarding fetal
karyotyping . (II-2 B).
3. Women with right-sided, biventricular, multiple, or
nonisolated EICF should be offered referral for expert
review and possible karyotyping . (II-2 A).

Face
 A series of transverse scans from the top of
the head moving caudally allows
examination of the forehead, nasal bridge,
orbits, nose, upper lip and anterior palate,
the tongue within the oral cavity, lower lip
and mandible.
 Each orbital diameter is equal in size to the
interorbital diameter.

Hypertelorism
 Hypertelorism is an increased
interorbital distance and this can
be either an isolated finding or
associated with many clinical
syndromes or malformations.

Hypotelorism (stenopia(:
Hypotelorism (decreased
interorbital distance) is almost
always found in association
with other severe anomalies,
such as holoprosencephaly,
trigonocephaly, microcephaly,
Meckel syndrome, and
chromosomal abnormalities.

FACIAL CLEFT
This term refers to a wide spectrum of clefting
defects (unilateral, bilateral and less
commonly midline) usually involving the
upper lip, the palate, or both
Prevalence:
1per 800 births. In about 50% of cases in both
the lip and palate are defective, in 25% only
the lip and in 25% only the palate involved.

Gastrointestinal tract
 Sonographically, the fetal stomach is visible from 9
weeks of gestation as a sonolucent cystic structure in
the upper left quadrant of the abdomen.
 The bowel is normally uniformly echogenic until the third
trimester of pregnancy,.
 The liver comprises most of the upper abdomen

Duodenal atresia
 Prevalence
 Duodenal atresia is found in about 1 per
5000 birth
 Diagnosis
 Prenatal diagnosis is based on the
demonstration of the characteristic ‘double
bubble’ appearance of the dilated stomach
and proximal duodenum, commonly
associated with polyhydramnios.

 Although the characteristic ‘double bubble’
can be seen as early as 20 weeks, it is
usually not diagnosed until after 25 weeks,
suggesting that the fetus is unable to
swallow a sufficient volume of amniotic fluid
for bowel dilatation to occur before the end
of the second trimester of pregnancy.
Duodenal atresia

Intestinal obstruction
 Prevalence
 Intestinal obstruction is found in about 1
per 2000 births; in about half of the
cases, there is small bowel obstruction
and in the other half anorectal atresia.
 Diagnosis
 Diagnosis of obstruction is usually made
quite late in pregnancy (after 25 weeks),.
as multiple fluid-filled loops of bowel in
the abdomen.
 Polyhydramnios (usually after 25 weeks)
is common, especially with proximal
obstructions

 Once an echogenic bowel is suspected, the
gain of the ultrasound unit is lowered
gradually until only bone or bowel is visible
 Definition
Bowel echogenicity equal to or greater than
bone is significant (grade 2 or 3)
. (II-2 A).
No further investigations are required for
grade 1 echogenic bowel . (II-2 D).
Echogenic bowel

Fetal bowel that is as echogenic as surrounding bone

Echogenic bowel
Echogenic bowel is diagnosed in 0.2%
to 1.4% of all second-trimester
ultrasounds.
It is associated with normal fetuses,
fetuses with aneuploidy, intrauterine
growth restriction (IUGR), intra-
amniotic bleeding owing to placental
abruptions, cystic fibrosis (CF),
congenital viral infections
(cytomegalovirus , herpes,
parvovirus, rubella, varicella, and
toxoplasmosis), and thalassemia.

Echogenic bowel
SO Expert review is recommended to initiate the following:
a. Detailed ultrasound evaluation looking for additional
structural anomalies or other soft markers of aneuploidy
.
(II-2 A)
b. Detailed evaluation looking for signs of bowel
obstruction and placental characteristics . (II-2 B).
c.Genetic counselling (II-2 A).
d. Laboratory investigations that should be offered,
including maternal serum screening, and testing for
congenital infection . (II-2 A)SOGC guidelines June 2005

ABDOMINAL CYSTS
 Abdominal cystic masses are frequent
findings. Renal tract anomalies or dilated
bowel are the most common explanations,
 Although cystic structures may arise from
the biliary tree, ovaries, mesentery or
uterus. the most likely diagnosis is usually
suggested by the position of the cyst, its
relationship with other structures and the
normality of other organs.

kidneys
 Longitudinal and transverse sections of
the abdomen can be used to study the
kidneys.
 The fetal bladder can be visualized from
the first trimester changes in volume
over time help to differentiate it from
other cystic pelvic structures.

Renal agenesis
 Prevalence
 Bilateral renal agenesis is found in 1 per 5000
births, while unilateral disease is found in 1
per 2000 births.
 Diagnosis
 Antenatally, the condition is suspected by the
combination of anhydramnios (from 17
weeks) and empty fetal bladder (from as early
as 14 weeks).

 Failure to visualize the renal arteries with
color Doppler is another important clue to the
diagnosis in dubious cases,
 Prenatal diagnosis of unilateral renal
agenesis is difficult because there are no
major features, such as anhydramnios and
empty bladder.
Renal agenesis

INFANTILE POLYCYSTIC
KIDNEY DISEASE (POTTER
TYPE I)
 Diagnosis
 is based on the
demonstration of
bilaterally enlarged and
homogeneously
hyperechogenic
kidneys. There is often
associated
oligohydramnios, but
this is not invariably
so.

MULTICYSTIC DYSPLASTIC
KIDNEY DISEASE (POTTER
TYPE II)
 Prevalence
 Multicystic dysplastic kidney disease is found in
about 1 per 1000 births.
 Diagnosis
 the kidneys are replaced by multiple irregular
cysts of variable size with intervening
hyperechogenic stroma. The disorder can be
bilateral or unilateral if bilateral, there is
associated anhydramnios and the bladder is
‘absent’.

obstructive uropathy
 The term ‘obstructive uropathy’ characterized by
dilatation of part or all of the urinary tract. When
the obstruction is complete and occurs early in
fetal life can lead to renal hypoplasia.
 On the other hand, where intermittent obstruction
allows for normal renal development, or when it
occurs in the second half of pregnancy,
hydronephrosis will result

Hydronephrosis
 Varying degrees of pelvicalyceal dilatation are
found in about 1% of fetuses.
 Mild pyelectasia. In about 20% of cases, there
may be an underlying ureteropelvic junction
obstruction or vesicoureteric reflux that
requires postnatal follow-up and possible
surgery.
 hydronephrosis, characterized by an
anteroposterior pelvic diameter of more than
10 mm and pelvicalyceal dilatation, is usually
progressive and in more than 50% of cases
surgery is necessary during the first 2 years of
life.

MILD
PYELECTASIS
Mild pyelectasis is defined as a
hypoechoic spherical or elliptical
space within the renal pelvis that
measures 5mm to 10 mm. The
measurement is taken on a
transverse section.

MILD PYELECTASIS
1. All fetuses with renal pelvic measurements 5 mm
should have a neonatal ultrasound, Renal pelvis
measurements > 10 mm should be considered
equivalent to congenital hydronephrosis and
should be considered for a third trimester scan
.
(II-2 A).
2. Isolated mild pyelectasis does not require fetal
karyotyping (II-2 E).
3. Referral for pyelectasis should be considered
with additional ultrasound findings and (or) in
women at increased risk for fetal aneuploidy
owing to maternal age or maternal serum screen
results .
(II-2 A).SOGC guidelines June 2005

Pulmonary abnormalities
 At 18-23 weeks, the central third of
the thoracic area at the level of the
four chamber view is occupied by
the heart, and the remaining two
thirds by the lungs, that are
normally uniformely echogenic.

PLEURAL EFFUSIONS
 Fetal pleural
effusions, which
may be unilateral or
bilateral, may be an
isolated finding or
they occur in
association with
generalized edema
and ascites.

DIAPHRAGMATIC
HERNIA
Prevalence
Diaphragmatic hernia is found in about 1 per
4000 births.
Diagnosis
 Diaphragmatic hernia can be diagnosed by
the demonstration of stomach and intestines
(90% of the cases) or liver in the thorax and
the associated mediastinal shift to the
opposite side.
 A left-sided diaphragmatic hernia, are easy
to demonstrate because the echo-free fluid-
filled stomach and small bowel. In contrast,
a right-sided hernia is more difficult to
identify

Cystic adenomatoid malformation
 Prevalence
 Cystic adenomatoid malformation of the lung
is found in about 1 in 4000 births.
 Diagnosis
 Prenatal diagnosis is based on the
demonstration of a hyperechogenic
pulmonary tumor which is cystic (CAM type
1), mixed (CAM type 2), or solid – microcystic
(CAM type 3)..
 In macrocystic disease, single or multiple
cystic spaces may be seen within the thorax.

Cystic adenomatoid malformation

Clubfoot
 The relationship of leg and foot should also be
assessed to rule out clubfoot

 Examination of the fetal brain can essentially be carried out by
two transverse planes, the transventricular and the
transcerebellar plane.
 The transventricular plane, obtained by a transverse scan at
the level of the cavum septum pellucidum will demonstrate the
lateral borders of the anterior (or frontal) horns, the medial and
lateral borders of the posterior horns (or atria) of the lateral
ventricles and the choroid plexuses.
The transventricular view is used for
measurement of the biparietal diameter (BPD),
head circumference (HC), and width of the ventricles.
 The transcerebellar (or suboccipitobregmatic) view allows
examination of the mid-brain and posterior fossa; this view is
used for measurement of the
transverse cerebellar diameter (TCD) and cisterna magna (CM).
CENTRAL NERVOUS
SYSTEM

 A sagittal and/or coronal view of the entire
fetal spine should be obtained in each case. In
the sagittal plane the normal spine has a
'double railway' appearance and it is possible
to appreciate the intact soft tissues above it.
 In the coronal plane, the three ossification
centers of the vertebra form three regular lines
that tether down into the sacrum.
CENTRAL NERVOUS
SYSTEM

NEURAL TUBE DEFECTS
 These include anencephaly, spina bifida and
cephalocele.
 In anencephaly there is absence of the cranial
vault (acrania) with secondary degeneration of
the brain.
 Encephaloceles are cranial defects, usually
occipital, with herniated fluid-filled or brain-filled
cysts.
 In spina bifida the neural arch, usually in the
lumbosacral region, is incomplete with secondary
damage to the exposed nerves.
 Prevalence:
 the prevalence is about 5 per 1,000 births.
Anencephaly and spina bifida, with an
approximately equal prevalence, account for 95%
of the cases and cephalocele for the remaining
5%.

Anencephaly
 Diagnosis:
 The diagnosis of
anencephaly during
the second trimester
of pregnancy is based
on the demonstration
of absent cranial vault
and cerebral
hemispheres.
Associated spinal
lesions are found in up
to 50% of cases.

Spina bifida
Diagnosis of spina bifida
requires the systematic
examination of each neural
arch from the cervical to the
sacral region both
transversely and
longitudinally.
In the transverse scan the
normal neural arch appears
as a closed circle with an
intact skin covering,
whereas in spina bifida the
arch is "U" shaped and
there is an associated
bulging meningocele (thin-
walled cyst) or
myelomeningocoele.

Spina bifida
 The diagnosis of spina bifida has
been greatly enhanced by the
recognition of associated
abnormalities in the skull and brain.
 These include frontal bone
scalloping (lemon sign), and
obliteration of the cisterna magna
with either an "absent" cerebellum
or abnormal anterior curvature of
the cerebellar hemispheres (banana
sign).

 Diagnosis:
 Fetal hydrocephalus is diagnosed sonographically,
by the demonstration of abnormally dilated lateral
cerebral ventricles10 mm or more. The choroid
plexuses, which normally fill the lateral ventricles
are surrounded by fluid.
 A distinction is usually made between mild
ventriculomegaly (diameter of the posterior horn
10-15 mm) and hydrocephalus (diameter greater
than 15 mm )
 Certainly before 24 weeks and particularly in cases
of associated spina bifida, the head circumference
may be small rather than large for gestation.,
HYDROCEPHALUS AND
VENTRICULOMEGALY

HYDROCEPHALUS AND
VENTRICULOMEGALY
 Prevalence:
Hydrocephalus is found in about 2 per
1,000 births.
Ventriculomegaly is found in 1% of
pregnancies at the 20-23 week scan.
Therefore the majority of fetuses with
ventriculomegaly do not develop
hydrocephalus.

MILD VENTRICULOMEGALY
. Mild ventriculomegaly
(MVM) is defined by
atrial measurements 10
to 15 mm.
Measurements are
obtained from an axial
plane at the level of the
choroid plexus.

HYDROCEPHALUS AND
VENTRICULOMEGALY

1. Fetal cerebral ventricles should be measured if they
subjectively appear larger than the choroid plexus (III-B).
2. Cerebral ventricles greater than or equal to 10 mm are
associated with chromosomal and central nervous system
pathology.
Expert review should be initiated to obtain the following:
a. a detailed anatomic evaluation looking for additional
malformations or soft markers. (III-B),
b. laboratory investigation for the presence of congenital
infection or fetal aneuploidy .
(III-B).
3. Neonatal assessment are important because of the
potential for subsequent abnormal neurodevelopment
. (II-
2 B).
MILD
VENTRICULOMEGALY

HOLOPROSENCEPHALY
 Diagnosis:
 In the standard transverse view of the fetal
head for measurement of the biparietal
diameter there is a single dilated midline
ventricle replacing the two lateral ventricles or
partial segmentation of the ventricles.
 The alobar and semilobar types are often
associated with facial defects, such as
hypotelorism or cyclopia, facial cleft and nasal
hypoplasia

MICROCEPHALY
 Microcephaly means small head and brain.
 Prevalence:
 Microcephaly is found in about 1 per 1,000
births. The diagnosis is made by the
demonstration of brain abnormalities, such
as holoprosencephaly.
 In cases with apparently isolated
microcephaly it is necessary to demonstrate
progressive decrease in the head to
abdomen circumference ratio to below the
1st centile with advancing gestation. Such
diagnosis may not be apparent before the
third trimester.
 In microcephaly there is a typical
disproportion between the size of the skull

CHOROID PLEXUS
CYSTS
Choroid plexus cysts (CPCs) are small
cysts
( 3 mm) found in the choroid plexus within
the lateral cerebral ventricles at 14 to 24
weeks .
Prevalence:
 Choroid plexus cysts are found in about
2% of fetuses at 20 weeks of gestation
but in more than 90% of cases they
resolve by 26 weeks.

Recommendations
1. Isolated CPCs require no further investigation when
maternal age or the serum screen equivalent is less than
the risk of a 35-year-old (II-2 E).
2. Fetal karyotyping should only be offered if isolated CPCs
are found in women 35 years or older or if the maternal
serum screen is positive for either trisomy 18 or 21 (II-2
A).
3. All women with fetal CPCs and additional malformation or
additional soft markers should be offered referral and
karyotyping (II-2 A).
CHOROID PLEXUS
CYSTS

Enlarged cisterna magna
If the cisterna magna is
subjectively increased, a
measurement should be taken
.
(III-B).
The mean diameter of a normal
cisterna magna is 5 mm, 10 mm
is considered an abnormality

Enlarged cisterna magna
1. An isolated enlarged cisterna magna is not an
indication for fetal karyotyping (III-D).
2. With an enlarged cisterna magna, look for other
anomalies, growth restriction, or abnormal
amniotic fluid volume. (III-B).
3. If the enlarged cisterna magna is seen in
association with other abnormal findings, fetal
karyotyping should be offered . (III-B).

 It must be emphasised that prenatal testing
is a two-edged tool; it can be used either
with a view to allow the opportunity for
prenatal counseling with a
multidisciplinary team of experts to permit
the planning of the mode and site of
delivery, thus ensuring optimal care of the
fetus and the newborn.
 , or it may be used with a view to selective
abortion in order to avoid the birth of a
disabled child.
 The tests themselves can give rise to great
worry and can be traumatic for the
pregnant woman, even if her baby is found
to be healthy.

Amniotic fluid
 Qualitative evaluation of amniotic fluid is accurate when
assessed by an experienced operator
 The volume of the amniotic fluid is evaluated by visually
dividing the mother's abdomen into 4 quadrants. The largest
vertical pocket of fluid is measured in centimeters. The total
volume is calculated by multiplying this value by 4.
 Polyhydramnios is usually defined as an amniotic fluid index
(AFI) more than 24 cm or a single pocket of fluid at least 8 cm
in deep that results in more than 2000 mL of fluid.
 Oligohydramnios is defined as an AFI less than 7 cm or the
absence of a fluid pocket 2-3 cm in depth.
E-medicine 3-2006

Prenatal ultrasonography
and oligohydramnios
 Levels less than 5 cm indicate significant
oligohydramnios.
 Visualize the fetal kidneys, collecting
system, and bladder. If these are normal,
suspect the chronic leakage of amniotic
fluid.
 Assess fetal growth. If PROM or urinary
tract anomalies are absent, consider
placental insufficiency and IUGR.
 Uterine artery Doppler study findings may
aid in the diagnosis of placental
insufficiency.

Prenatal ultrasonography and
polyhydramnios
 Evaluate fetal swallowing. A decrease in fetal
deglutition occurs in anencephaly, trisomy 18,
trisomy 21, muscular dystrophy, and skeletal
dysplasia.
 Evaluate the fetal anatomy; assess for
diaphragmatic hernia, lung masses, and the
absence of the stomach bubble (which is
associated with esophageal atresia). The double-
bubble sign or a dilated duodenum suggests the
possibility of duodenal atresia.
 An abnormally large abdominal circumference may
be observed with ascites and hydrops fetalis or a
macrosomic fetus; these findings are also
observed in association with poorly controlled
maternal diabetes.

PLACENTAL
LOCALISATION
 The relationship between
the lower margin of the
placenta and the internal
os should be determined.

Definition
 Placenta previa is a placental
implantation that overlies or is within 2
cm of the internal cervical os.
 a complete previa when it covers the os
 a marginal previa when the edge lies
within 2 cm of the os.
 Low lying when the edge is 2 to 3.5 cm
from the os.

placenta praevia
 Ultrasound Findings..
 The maternal urinary bladder may be used as
a landmark to identify the location of the
internal cervical os.
 The most common conditions that cause
a false diagnosis of placenta previa are
an overdistended bladder and
myometrial contractions.

Accreta, Increta, Percreta
 Placenta accreta is the abnormal
adherence of part or all of the
placenta with partial or complete
absence of the decidua basalis.
 Placenta increta is further extension
of the placenta through the
myometrium.
 Placenta percreta is penetration of
the uterine serosa.

Risk factor
 PP with
 Unscarred uterus, 1 to 5 percent
 One previous cesarean birth, 25%
 Two previous cesarean births, 40%
 Four or more previous cesarean births,
50 to 67 %
 Other risk factors include maternal age
>35 years, endometrial defects
(Ascherman syndrome), and
submucous leiomyomata.

The most prominent gray scale features
to suggest placenta accreta are:-
• (1) loss of the normal hypoechoic
retroplacental myometrial zone.
• (2) thinning or disruption of the
hyperechoic uterine serosa-bladder
interface.
• (3) the presence of multiple lakes that
represent dilated vessels extending
from the placenta through the
myometrium.

newly formed vessel + multiple
placental lakes

The uterine segment is
shown totally destroyed.

the multiple layers of newly
formed vessel between uterus
and the bladder

Color-flow Doppler ultrasonogram
demonstrating placenta percreta with bladder
invasion.

Placental size
Placentomegaly
On ultrasound the placenta thickness measures
more than 5 cm. Maternal diabetes and Rh
incompatability are primary causes for
placentomegaly
Other causes include :
Maternal anemia, a-thalassemia, Chronic
intrauterine infections ,twin-twin transfusion
syndrome, Congenital neoplasms and fetal
malformations
SmallPlacenta:
IUGR,, Intrauterine infection, Chromosomal
abnormality

Abruptio Placenta
 Ultrasound Findings Upon examination of
the placenta, the sonographer will notice an
abnormality in the texture and size of the
placenta. If a hemorrhage is present, the
echogenicity depends on the age of the
hemorrhage; the acute bleed is hyperechoic
to isoechoic while the chronic bleed is more
hypoechoic.

hydatidiform mole
 Ultrasound Findings
 uterine size larger than dates, no identifiable fetal parts,
inhomogeneous texture of the placenta that represent the
multiple vesicular changes. Bilateral theca luetin cysts are seen
in the ovaries.
 A partial mole is associated with an abnormal fetus or fetal
tissue. On ultrasound a reduced amount of amniotic fluid is
noted. The placenta is thick with multiple intraplacental cystic
spaces.
 A coexistant mole and fetus is very rare; the mole may result
from a hydatidiform degeneration of a twin fetus. This condition
is more likely when two placentas are present. The abnormal
placenta is hyperechoic with multiple small cysts. The coexisting
fetus is live with a normal placenta.

Chorioangioma
 A benign vascular tumor of the placenta.
 Second to trophoblastic disease, chorioangioma is the
most common "tumor" of the placenta, occurring in 1%
of pregnancies.
 Complications include polyhydramnios, premature labor,
fetal hydrops, fetal cardiomegaly, intrauterine growth
retardation, and fetal demise. The maternal serum AFP
may be elevated.
 Ultrasound shows a circumscribed solid or complex
mass that protrudes from the fetal surface of the
placenta. It may be located near the umbilical cord site.

Placental grading
 Grade 0
 Late 1st trimester-
early 2nd trimester
 Uniform moderate
echogenicity
 Smooth chorionic
plate without
indentations

Placental grading
 Grade 1
 Mid 2nd trimester –
early 3rd trimester
(~18-29 wks)
 Subtle indentations
of chorionic plate
 Small, diffuse
calcifications
(hyperechoic)
randomly dispersed
in placenta

Placental grading
 Grade 2
 Late 3rd trimester
(~30 wks to delivery)
 Larger indentations
along chorionic plate
 Larger calcifications
in a “dot-dash”
configuration along
the basilar plate

Placental grading
 Grade 3
 39 wks – post dates
 Complete
indentations of
chorionic plate
through to the basilar
plate creating
“cotyledons”
 More irregular
calcifications with
significant
shadowing

Prenatal diagnosis of congenital anomalies 3

Prenatal diagnosis of congenital anomalies 3

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