2. INTRODUCTION Detailed
second
trimester
scan for
assessing
fetal anatomy
A screening
Ideal period
test and a Level II 18 to 22
diagnostic test
for fetal ultrasound weeks of
gestation.
anomalies.
To predict structural
normalcy of the fetus
To identify severe&
lethal abnormality
To raise suspicion of
an abnormality
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3. Level II ultrasound
How to start
LMP
Family History
First and foremost History
High risk/ low risk
Assessment
Amniotic fluid Placenta Umbilical cord
Gestational age by
Location, appearance Number of
fetal biometry
relation to internal os vessels
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4. Fetal biometry
BPD
Any plane with B/L
thalami and third
ventricle.
Maximum transverse
diameter from the outer
edge of near calvarial wall
to the inner edge of the
distal calvarial wall.
4
5. Head circumference
Go more cephaled
anteriorly for the plane
which will include
Image
Third ventricle
Thalami
Cavum septum pellucidum
Basal cisterns
Measure outer edge
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6. Femur length
Transducer aligned to long
axis of diaphysis
Image
Measure only ossified
portion.
To ensure full length, see the
soft tissue beyond the both
ends
Bone should not appear
merging with skin at any
point.
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7. Abdominal circumference
AC (abdominal
circumference) measures the
outer perimeter of the Image
abdomen
At the level of stomach and
intra-hepatic part of
umbilical vein.
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8. The intracranial anatomy
Views for cerebral ventricle,
Thalami and third ventricle,
The cerebellum and cistern
magna.
For ventricles up to 20 weeks
it is the same view taken for
BPD. It show both anterior
posterior horns and the body
of the lateral ventricle.
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9. Ventriculomegaly
Ventricle should measured
from outer to outer wall.
In ventriculomegaly atrial
diameter >10mm
Ventricle to choroid
distance >3 mm,
V/H ratio > 2.8
Drooping /dangling
choroid plexus.
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10. Choroid plexus cyst
Seen in I-6% of fetus
Cystic area in choroid plexus,
Typically small <10 mm
Can be unilateral or bilateral
Usually resolves by 26 weeks
of gestation.
Can be associated with
trisomy I8
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12. Corpus callosal agenesis
• Corpus callosum begins to
develop at 12 wk & fully formed
by 20 wk
• CSP seen by 17 wk
• Absence of CSP at 17-20 wk-
suspect ACC
Colpocephaly
Too many sulci perpendicular to
interhemisphere
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13. For cerebellum
Sub-occipito-bragmatic view
It is dumb bell shaped has two
lateral lobes and triangular
shape connection vermis.
Complete or partial
absence or anterior
displacement of
vermis associated
with spectrum of
Dandy walker
malformation.
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14. Nuchal fold thickness,
Measured from the outer
border of occiput to
outer border of skin Image
echoes
>6 mm considered to be
increased
strong marker of trisomy
21.(detection rate of 90%
with false positive in
5%.) cystic hygroma and occipital
encephalocele can be seen in this region
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15. Fetal spine
Screen in all three planes sagittal, transverse and coronal
For three ossification centre with intact overlying skin.
For sagittal place the probe just over the spine and screen the
whole spine from CVJ to upsweep of the sacrum,
Distance of the skin from the spine should be equal
Image Image
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16. Fetal spine
Transverse view- Three ossification centres are seen in
triangular shape
Screen all the vertebra with slight curve of overlying skin
especially in sacrum.
In coronal view 3 parallel echoes are seen with equal
distance .
In this manner we can diagnose spina bifida and
meningo/myelocele.
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17. Spina bifida
Results from incomplete closure
of bony element of spine
posteriorly
It can be open or closed.
Most common site is lumbo-
sacral region.
In open spina bifida we should
look for secondary cranial signs
like lemon sign and banana
sign.
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18. Fetal chest and diaphragm
Most important structure is heart in
the thorax.
Any hypoechoic area other than
heart - suspect diaphragmatic hernia
80% on the left side and stomach
and bowel are the abnormal organ.
Heart is often pushed to right side of
the chest.
In right sided hernia liver is most
likely to herniated in the chest.
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19. Fetal chest
Congenital cystic
adenomatoid malformation:
•Stocker’s classification- I, II, III
•Azdick’s 2 forms- macrocystic &
microcystic
•Mediastinal shift & hydrops can
occur
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20. Fetal heart
Four chamber view,
The aortic outflow tract,
The pulmonary artery outflow
tract
The crossover of aorta and
pulmonary artery
The heart rate.
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21. In four chamber view
The two ventricles and
ventricular walls should be of
equal size.
Two atria and atrial walls
should be of equal size
Moderator band should be
seen in right ventricle
Motion of the mitral and
tricuspid valve should be
regular
Inter-ventricular septum
should be complete
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22. Fetal heart
Aortic outflow tract this view shows
continuity of inter-ventricular
septum with the anterior wall of
aorta.
Pulmonary outflow tract shows the
continuity of right ventricle wall
with the pulmonary artery –
abnormal in double outlet RV and
pulmonary stenosis.
The cross over, above two vessels
crossover each other when leaving the
heart. It excludes the TGA
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23. 3 vessel view
SVC, Aorta and Pulmonary
artery.
Fetal heart rate should be
regular(110-150 bpm)
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24. Fetal abdomen
Look for normal stomach bubble,
It will be seen after 16 wks. If absent rescan after 20
min.
Still not seen suspect oesophageal atresia.
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25. Another bubble is seen adjacent to stomach bubble other
than gall bladder suspect duodenal atresia(double bubble)
D/D include large choledochal cyst.
Duodenal bubble is equal to or smaller than stomach bubble
and shows communication with the stomach,
Whereas choledochal cyst can be larger than stomach and
does not show any communication .
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26. Fetal abdomen
Fetal liver –left lobe is larger in fetus
Gall bladder –located to the right side of intra-
hepatic umbilical vein
Fetal spleen-not amenable to scan in second
trimester.
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27. Coming to the bowel
Dilated bowel can be seen in
abdomen indicative of
obstruction.
It should be >7mm in small
bowel
>20mmin large bowel
obstruction
Echogenic bowel called when
it appears as echogenic as
bones.
It is also a soft marker of
chromosomal anomaly with
increased risk of trisomy of
21.
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28. Anterior abdominal wall
Look for intact anterior abdominal
wall with cord insertion
Anterior abdominal wall defect i.e.
omphalocele, gastroschisis.
Omphalocele develops due to
failure of fusion of two lateral folds
of anterior abdominal wall
gut herniates into the base of
umbilical cord.
it is covered by protective layer of
peritoneum and amnion
The umbilical cord inserts into apex
of the defect .
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29. Gastroschiasis
Body folds fused normally
A small defect arise in the
abdominal wall usually below
the cord insertion.
Cord insertion is seen normal.
It is thought to be due to
vascular compromise.
Gut floats freely into the
amniotic fluid
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30. Fetal hydrops
Abnormal accumulation of
fluid in at least 2 body
cavities/ tissues or single
serous collection and
anasarca
• Ascites
• Pleural effusion U/L or B/L
• Edema- generalized/
localized/ limited-Earliest
seen over fetal scalp or face
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31. The urinary tract
Fetal kidneys can be seen from 14
wks of gestation trans-abdominal
Best located from transverse section
seen in para-spinal gutters.
Kidneys can be identified through
the renal arteries if not clearly
visible.
In renal agenesis renal arteries are
also absent, unilateral or bilateral.
Bilateral renal agenesis is associated
with oligo or anhydramnios.
32. MILD RENAL PELVIC DIALATION
Renal pelvis AP diameter should
taken inner to inner aspect of
pelvis outline in transverse section.
4-5 mm is taken as upper limit in
second trimester and 10mm in
third trimester.
mild renal pelvic dilatation
constitutes a minor marker of
chromosomal anomaly including
trisomy 21.
Re-scanned between 32-36 wks.
33. Cystic renal disease
Multicystic dysplastic kidney (MCDK)
Kidney- enlarged & replaced by multiple cysts with
no functioning parenchyma in between
A/w atretic ureter & pelvi-infundibular atresia
ARPKD
B/L with Numerous 1-2 mm cysts
Enlarged kidneys with smooth outline, raised
echogenicity & lost CMD
Oligohydroamnios & small/absent UB
ADPKD
Cysts in kidneys & liver
Small cysts
B/L enlarged echogenic kidneys
UB usually seen with normal AFV 33
34. Fetal bladder
Usually visible trans-abdominally
from 12 wks of gestation.
Normally it empties every 30 to
45 min.
Demonstration of filling of
bladder implies normal function
and exclude bilateral renal
agenesis.
35. Obstructive uropathy
Presents with bilateral hydro-uretero-nephrosis .
Common cause posterior urethral valve.
Present with over distended bladder with distended
proximal urethra gives a typical key hole appearance.
Other causes includes urethral atresia
36. Fetal limbs
Confirm the three long bones in
all four limbs
Presence of two hands and two
feet with normal carrying angle.
Absent limb
Complete absence-amelia
Partial absence-meromelia
Absence of long bone with hand
and feet attach to the body
called phocomelia.
37. Skeletal dysplasia-key features
Shortening of limbs
entire limb-micromelia
Humerus / femur –rhizomelia
Both bone forearm/leg-mesomelia
Defective mineralization and/or fracture
Additional features like appearance of thorax, rib and
skull.
38. Fetal limbs
All long bones should be
scanned in longitudinal
section.
These should be straight
and symmetrical.
AP view of tibia and fibula-
only talus should be seen.
If foot print view is
obtained talipus should be
suspected, it is associated
with trisomy of 18 and 13
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39. Fetal limbs
lateral view of lower leg shows foot
in sagittal section - exclude
rocker bottom foot which is
associated with trisomy 18.
A planter view of foot exclude
polydactyly/syndactyly exclude
sandal gap ,which is associated
with trisomy 21 and triploidy.
40. Hand
Outstretched hand view - to
confirm normal appearance of
forefingers and thumb to
exclude
clinodactyly/polydactyly.
Hypoplasia of proximal
phalanx of fifth digit is
associated with trisomy 21.
Clenched fist with overlapping
index finger associated with
trisomy of 18
41. Fetal face
Few views are important
Nose lip view
Facial profile view
Axial views of orbit,
maxilla and mandible
Mid face coronal view.
42. Eyes and orbit
orbits should be symmetrical
separated by a distance equal
to size of an orbit.
Lenses should be seen with in.
Intra-occular distance varies in
hypotelorism and
hypertelorism.
43. Profile view(sagittal midline)
Assessment of forehead, nose
and chin
Anomalies can be seen are
Frontal bossing, flat nose,
Micrognathia-when mid part of
mandible not align with maxilla
macroglossia-persistent
protrusion of the tongue
44. Cleft lip/cleft palate
Two views are important
Nose lip view(coronal face)
Axial view of maxilla(alveolar
ridge)
46. 3D & 4D ULTRASOUND
• 3D US- Acquisition of a series of 2D
images over a volume f/b image
display in different orientations
• 2 methods – free hand acquisition &
automated acquisition
• 4D US- 3D US displayed over time
• Especially helpful in depicting
facial anomaly, skeletal dysplasia
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47. Conclusions
The continuing improvement in resolution of ultrasound
systems gives us ability to identify an ever-increasing
range of abnormalities in the fetus
Diagnosis of anomaly : opportunity for counseling,
termination, or tertiary level care
Benefits : Reassurance of normal pregnancy
At least 20 minutes should be allocated for the
examinations
New advances like 3D & 4D US- can be a problem
solving tools in evaluation of some anomalies.
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