Mid-Trimester Fetal Ultrasound Scan - PowerPoint Presentation

Slide1

Mid-Trimester Fetal Ultrasound Scan

E,Keshavarz

MD

Assistant Professor of Radiology

SBMU

Slide2

ISUOG

(

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)

Slide3

Routine 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

Slide4

Indications 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

Slide5

FETAL 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)

Slide6

AMNIOTIC 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.

Slide7

Slide8

: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

Slide9

SKULLsize, 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.

Slide10

Brain

Transventricular

Transthalamic

Transcerebellar

Slide11

The following brain structures should be evaluated:

lateral ventricles (including choroid

plexi

)

cavum

septi

pellucidi

thalami

cisterna magna

Cerebellum

Slide12

Face

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

.

Slide13

Slide14

NB

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%

Slide15

Neck

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

.

Slide16

THORAX

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)

Slide17

Fetal 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

.

Slide19

A

large echogenic

structure lying within

the

right

ventricle

, the

muscular

moderator

band

.

Slide20

The heart is normally deviated about 45 ± 20 degrees (2 SD) toward the left side of the fetus.

Slide21

A 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

Slide22

Four-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

.

Slide23

Four-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

Slide24

Four-Chamber View

The tricuspid valve

lower

in position within the right ventricle than is the mitral valve within the left ventricle.

Slide25

Echogenic

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.

Slide26

Pseudopericardial 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.

Slide27

An ‘

extended basic

’ evaluation which includes

the

aortic and pulmonary outflow tracts

Right outflow tract

Left outflow tract

head

Rt.shoulder

Slide28

3 vessels

view:are

approximately

equal

in size

Slide29

normal crisscross relationship of the pulmonary artery and aorta

Transposition of the great arteries

Slide30

A 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

.

Slide31

Tachycardia

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

Slide32

Congenital 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)

Slide33

ABDOMEN

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

.

Slide34

The 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.

Slide35

KIDNEYS 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.

Slide36

SPINE

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

Slide37

SPINE

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.

Slide38

LIMBS 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

.

Slide39

Humerus

length /HL

Slide40

Genitalia

Characterization of external genitalia, to determine fetal gender ,

is not considered mandatory

in the context of a mid-trimester routine scan.

Slide41

CERVIX, 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)

Slide42

CERVIX, UTERINE MORPHOLOGY AND ADNEXA

High risk population

:

-

Hx

of PTB

-

Hx

of PROM

-

Hx

of cervical surgery

-

Uterocervical

anomalies

- Multiple gestation

- Fetal therapy

- Polyhydramnios

Slide43

CERVIX, UTERINE MORPHOLOGY AND ADNEXA

Slide44

Minimal

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

)

Slide45

Chest/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

Slide46

Age 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

Slide47

The most widely examined markers :

Slide48

The pooled estimate of the positive LR

Slide49

The 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.

Slide50

IF NO SOFT MARKER :

Revised risk = Prior risk * 0.15

Slide51

Slide52

Thanks