EKeshavarz MD Assistant Professor of Radiology SBMU ISUOG I nternational S ociety of U ltrasound in O bstetrics and G ynecology AIUM A merican I nstitute of ID: 935649
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Slide1
Mid-Trimester Fetal Ultrasound Scan
E,Keshavarz
MD
Assistant Professor of Radiology
SBMU
Slide2ISUOG
(
I
nternational
S
ociety
of
U
ltrasound in
O
bstetrics and
G
ynecology
)
AIUM
(
A
merican
I
nstitute of
U
ltrasound in
M
edicine
)
FMF
(
F
etal
M
edicine
F
oundation)
Slide3Routine ultrasound scan
Level 1
Simple (viability –GA )
Level 2
( standard 18 W G )
Detailed scan at 18 – 20 weeks
to establish abnormality in all system
Level 3
Targeted US
Slide4Indications for a Level II scan may include:
Suspicious findings on a Level I scan
History of prior congenital anomaly
Insulin dependent diabetes or other medical problem that increases the risk of anomaly.
History of seizure disorder, particularly if being treated with medications known to increase the risk of anomaly.
Teratogen
exposure
Elevated MSAFP
Suspected chromosome abnormality
Symmetric IUGR
Fetal arrhythmia
Oligohydramnios
,
hydramnios
Advanced maternal age
Slide5FETAL BIOMETRY AND WELL BEING:
1.
Biparietal
diameter (BPD)
2. Head circumference (HC)
3. Abdominal circumference (AC)
4. Femur diaphysis length (FL)
5.
Humerus
length (HL)
Slide6AMNIOTIC FLUID ASSESSMENT
Subjective estimation
is
not inferior
to the quantitative measurement techniques (e.g.
deepest pocket
,
amniotic fluid index
) when performed by experienced examiners
Patients
with deviations from normal should have more detailed anatomical evaluation and clinical follow up.
Slide7Slide8:SKULL
size
, shape, integrity and bone
density
Shape
:
The skull normally has an
oval
shape
without focal protrusions or defects
.
Alterations
of shape (e.g.
lemon
,
strawberry
,
cloverleaf
,
etc
) should be documented and
investigated.
Integrity
:
No bony defects
should be
present ,interrupted
only by narrow
echolucent
sutures.
Brain
tissue can extrude through defects of the frontal or occipital bones although
cephaloceles
may occur at other sites as well
Slide9SKULLsize, shape, integrity and bone density
Density
:
Normal skull density is manifested as a
continuous echogenic
structure.
The
absence of this whiteness or extreme
visibility of the
fetal
brain
should raise suspicion of poor mineralization (
osteogenesis
imperfecta
,
hypophosphatasia
).
Poor mineralization is also suggested when the skull becomes
easily depressed
as a result of manual pressure from transducer placement against the maternal abdominal wall.
Slide10Brain
Transventricular
Transthalamic
Transcerebellar
Slide11The following brain structures should be evaluated:
lateral ventricles (including choroid
plexi
)
cavum
septi
pellucidi
thalami
cisterna magna
Cerebellum
Slide12Face
Both
orbits/
Lenses
Evaluation of the nose/ nostrils
Presence of the mouth
Coronal view of the upper lip
can
be used to identify cleft lip anomalies.
If
technically feasible,
a median facial profile view can be
obtained
.
Slide13Slide14NB
Unilateral or bilateral
hypoplastic
/absent
4/4.5/5 mm for 18/19/20 week
NBL/PT:
Normal
1.48 to 1.79 between 14 and 28 weeks
NBL/PT < 80%
spe
50%
Slide15Neck
This structure should be cylindrical with no protuberances, masses or fluid collections.
Detailed
neck
anatomy
is
not
part of the screening examination although this
region can
be evaluated in transverse and sagittal planes
.
Slide16THORAX
The
shape
should be
regular
with a smooth transition to the abdomen
.
The
ribs
should have normal curvature without deformities.
Both
lungs
should appear homogenous and without evidence for
mediastinal
shift or masses.
The
diaphragmatic
interface can often be visualized as a
hypoechoic
dividing line between the thoracic and abdominal content (e.g. liver and stomach)
Slide17Fetal Heart
Basic cardiac examination
Extended basic cardiac examination
Slide18‘Basic cardiac’ examination:
The basic cardiac screening examination is interpreted from a
four -chamber view
of the fetal heart.
The heart should be located in the left chest (same side as the fetal stomach) if the
situs
is normal
.
Slide19A
large echogenic
structure lying within
the
right
ventricle
, the
muscular
moderator
band
.
Slide20The heart is normally deviated about 45 ± 20 degrees (2 SD) toward the left side of the fetus.
Slide21A normal heart is usually no larger than
one-third
the area of the chest
In
four-chamber view; approximately three fetal hearts can fit into the fetal thorax
Slide22Four-Chamber View
The left atrium lying close to the vertebral column.
The
left atrium is posterior in location in comparison with the right atrium
.
The
foramen
ovale
is noted
opening from the
right
atrium into
the left atrium
.
Slide23Four-Chamber View
Anatomically,the
right ventricle
is
behind the sternum
, and the
left
ventricle is
inferior
.
Left
atrium to right atrium
ratio
approximately
1:1
Left
ventricle to
right ventricle
ratio approximately 1:1
Slide24Four-Chamber View
The tricuspid valve
lower
in position within the right ventricle than is the mitral valve within the left ventricle.
Slide25Echogenic
intracardiac
foci (EIF) is a common finding during the second trimester, observed in 3-4% of normal fetuses. The prevalence among normal fetuses appears to be significantly higher among Asian populations, in the range of 10-15
%.
COULD BE ARTIFICIAL.
Slide26Pseudopericardial Effusion
normal
hypoechoic
myocardium should not be mistaken for a pericardial
effusion.
Normally, a small amount of pericardial fluid may be
observed
.(<2mm)
This fluid is observed more prominently during ventricular
systole.
Slide27An ‘
extended basic
’ evaluation which includes
the
aortic and pulmonary outflow tracts
Right outflow tract
Left outflow tract
head
Rt.shoulder
Slide283 vessels
view:are
approximately
equal
in size
Slide29normal crisscross relationship of the pulmonary artery and aorta
Transposition of the great arteries
Slide30A normal
regular rate
ranges from 120 to 160 beats per minute.
Mild
bradycardia
(<100)is
transiently
observed
in
normal
second-trimester fetuses
.
If sinus bradycardia is less than 80 beats/min ,fetal
asphyxia
should be in mind
Fixed
bradycardia
,
especially heart
rates that remain below 110 beats per minute
, requires timely evaluation for possible heart block.(SLE) Mild tachycardia (>180 beats per minute) can occur as a normal variant during fetal movement.Persistent
tachycardia
, however
, should be further evaluated for
possible fetal
distress or more serious
tachydysrhythmias
.
Slide31Tachycardia
PACs
are more frequent than
PVCs
.Could be conducted or blocked.
Paroxysmal SVT
: Atrial 180-300 / conductive rate 1:1
Atrial flutter
: Atrial 300-400 /conductive rate 2:1 or 4:1
regular
ventricular response 60 -200
Atrial fibrillation
: Atrial >400 and
irregular
ventricular response 120-160
Slide32Congenital heart block
First degree block
: Prolonged PR interval with normal rate or
rhythm(NO
diagnosis in
utero)
Second degree block
:
Mobitz
type 1
:blockage of a single atrial beat (PR distances are increased until one of the Ps doesn’t have R)
Mobits
type 2
:intermittent conduction abnormality( 3 P 2 R)/ ventricular rate is a fraction of the atrial rate
Third degree block
: A and V rates are entirely dissociated normal
regular
P(A) rate but bradycardic
regular
R(V)
Slide33ABDOMEN
Stomach(presence, size,
situs
)
bowel
umbilical
cord insertion and intact abdominal wall
3
vessel cord
Bowel normal echogenicity (normally less than bone) and absence of abnormal
fluid collections
should be confirmed. cystic structures seen in the abdomen should be referred for a targeted ultrasonography
.
Slide34The fetal umbilical cord
insertion
site should be examined for evidence
of a
ventral wall defect such as
omphalocele
or
gastroschisis
.
The
number
of umbilical arteries can be confirmed by a transverse view of the umbilical
cord,
color
Doppler ultrasonography allows
rapid confirmation
of these vessels as they
course around
the
fetal
bladder.
Slide35KIDNEYS AND BLADDER
The fetal bladder and both kidneys should be identified
.
If either the
bladder(
more than 30mm
)
or renal
pelvis(
more than 4mm
)
appear enlarged, a measurement should be
documented.
Persistent failure to visualize the bladder (25’-30’)should prompt a referral for a more detailed assessment.
Slide36SPINE
The spine and its skin covering should be assessed in
sagittal
and
transverse
/axial ,coronal sections. Other view may identify other spinal malformations including vertebral abnormalities and sacral agenesis.
It is heavily dependent upon the fetal position
Slide37SPINE
Normal
appearances of
the
spine, its skin covering and the intracranial anatomy together with the shape of the skull should exclude 90% of cases of
open
spina
bifida
, as a most frequent severe spinal abnormalities.
Slide38LIMBS AND EXTREMITIES
The presence or absence of both arms/hands
and
both legs/feet
should
be documented using a systematic
approach.
Counting
fingers
or toes
is
not
required as part of the basic scan
.
Slide39Humerus
length /HL
Slide40Genitalia
Characterization of external genitalia, to determine fetal gender ,
is not considered mandatory
in the context of a mid-trimester routine scan.
Slide41CERVIX, UTERINE MORPHOLOGY AND ADNEXA
There is
insufficient evidence
to recommend routine
cervical length
measurements at mid trimester in an unselected population
.
General population : TAS before 30 week(NL:30 mm)
High risk population :TVS from 14 week (NL:25mm) ….24(every 2 weeks until 30 week)
Slide42CERVIX, UTERINE MORPHOLOGY AND ADNEXA
High risk population
:
-
Hx
of PTB
-
Hx
of PROM
-
Hx
of cervical surgery
-
Uterocervical
anomalies
- Multiple gestation
- Fetal therapy
- Polyhydramnios
Slide43CERVIX, UTERINE MORPHOLOGY AND ADNEXA
Slide44Minimal
Requirements
Head
intact
cranium
cavum
septi pellucidi
midline
falx
thalami
cerebral
ventricles
cerebellum
cisterna magna
Face
presence
of both orbits
median
facial profile*
upper
lip intact
mouth present
Neck
absence
of masses (e.g. cystic
hygroma
)
Slide45Chest/Heart
normal
appearing shape and size
presence
or absence of heart activity
four-chamber
view of the heart in normal position
aortic
and pulmonary outflow tracts*
no
evidence for diaphragmatic hernia
Abdomen
stomach
in normal position
bowel
pattern
kidneys
cord
insertion site
Skeletal
no
spinal defects or masses (transverse and
sagittal
views)
arms
and hands present, normal relationships
legs
and feet present, normal relationships
Slide46Age Adjusted Ultrasound Risk Assessment (AAURA) Nyberg/Second trimester genetic sonogram
Only in 14-20 weeks.
As a result, AAURA was falsely positive in only 4% of women under age 35.
Risk by
age,biochemistery
and US.
Amniocentesis threshold:1/250-1/270
Slide47The most widely examined markers :
Slide48The pooled estimate of the positive LR
Slide49The findings of this meta-analysis confirm that the incidence of each of the selected second-trimester
sonographic
markers is higher in
trisomy
21 than in
euploid
fetuses.
Slide50IF NO SOFT MARKER :
Revised risk = Prior risk * 0.15
Slide51Slide52Thanks