Obstetric Ultrasound final-1.pptx

Basic concepts of Ultrasonography
10/25/2023 1
By Alemayehu Nigussie

Out lines
• Introduction
• Brief on indications of US in obstetrics & the techniques
• Review pelvic Anatomy
• Early pregnancy & signs of abnormalities
• 1st , 2nd & 3rd TMP
• Pregnancy dating
• Multiple gestations
• Placenta and umbilical cord
• Assessment of amniotic fluid
• BPP
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• What is sound?
• What is ultrasound?
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• Ultrasound = sound waves with frequencies above the
audible range for human ears.
• Sound waves are mechanical waves.
• So, require a medium for propagation
• The speed of ultrasound waves in tissues is about
1540m/s. (bones ~3000m/s)
Physics and technical principles
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US Pulse-Echo Technique
Ultrasound
transducer
Tissue Interface
Pulse
Echo
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• Interaction of US waves with tissues:
-partially absorbed
-reflected
-scattered
• Whether reflected or back scattered, echoes are
received by transducer
• The echoes are source of diagnostic information
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• Bone, gas and FBs (metallic, non metallic) cause very
strong reflection (acoustic shadow) – obstacles
US examination may also be limited by:
Surgical wounds
 dressings
skin lesions, which preclude firm transducer
contact with the skin
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8
Why ultrasound is technique of choice?
• Allows real time assessment
• Doesn’t employ ionizing radiation
• Used in any chosen plane
• Less expensive than CT or MRI
• Portable
• Relatively safe and non-invasive
10/25/2023 By Alemayehu Nigussie

• Misinterpretation of US images is a significant risk in
ultrasound diagnosis
• US scanning is operator dependent
• The skill of effective scanning lies on:
 operator’s ability to maximize diagnostic information available
 ability to interpret appearances properly
• This is dependent upon:
-clinical knowledge
-technical skill
-knowledge of the equipment being used
Image optimization
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Ultrasound Machine
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TRANSDUCER
• US imaging is performed with pulse-echo
technique
• US transducer converts electrical energy to a brief
pulse of high-frequency sound energy that is
transmitted into patient tissues.
• US transducer then becomes a receiver, detecting
echoes of sound energy reflected from tissue.
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Types of US scan in Early Pregnancy
• Transabdominal
• Transvaginal
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Frequency- the number of waves that pass a fixed
point in unit time.
The higher the frequency
 better resolution
 high attenuation
 a limited penetration depth
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Transabdominal US(TAS)
PROS
 Easier to identify anatomy
3.5 MHz frequency
 Easier to visualize structures
outside of uterus
 Lower frequency allows better
penetration, widening field of view
CONS
• Bladder must be full
• Less detail, especially in
very early pregnancy
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Transvaginal US
PROS
• More detailed visualization
of uterus
• 7MHz frequency
• Do not need full bladder
CONS
• Difficult to visualize
structures outside the
uterus
• Shallow field
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• Use a 3.5 MHz transducers for adults
• Use a 5 MHz transducer for children
and thin patients
Choice of transducer( Prob)
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PROBE ORIENTATION
Sagittal Orientation
 Sagittal - probe marker points toward
patient’s head
Superior is to the LEFT of the monitor.
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Transverse Orientation
 Transverse -probe marker points toward
patient’s right
Patient’s left is at RIGHT of monitor.
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Transducer Orientation
 Proper transducer orientation is achieved when
monitor image “appears” to move in opposite direction
from transducer movement!
proper handling of the prob
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PREPARING TO SCAN
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• 4 possible movements:
i- Sliding
ii- Rotating
iii- Angling &
iv- Dipping
Probe movements (TAS)
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1. Sliding:
-by holding probe longitudinally or transversely &
sliding it from side to side or up and down
-useful for keeping a structure that is being examined in
center of u/s screen
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2. Rotating:
-describes rotation of probe about a fixed point
-allows a longitudinal section to be obtained from a
transverse section of an organ (or vice versa) while keeping
the organ in view
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3. Angling:
-describes an alteration of angle of complete probe
surface relative to skin surface
-its main use is for obtaining correct sections from slightly
oblique views
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4. Dipping:
-describes pushing one end of prop into abdomen
-can be uncomfortable, so should be done as gently as
possible
-brings structures of interest to lie at right angles to the
sound beam
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Prob movements on TVS
Like that of TAS there are four possible prob
movements on TVS.
These are:-
1- Sliding
2- Rotating
3- Rocking
4- Panning
All movements of transvaginal probes should be carried
out slowly and gently.
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Basic scanning movements with the transvaginal probe.
A. Sliding;
B. rotation;
C. panning.
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• Necessary to ensure good acoustic contact between
transducer and the skin
• Water is not ideal and is useful only for very short
examinations
• Disinfectant fluids can be used especially for guided
punctures
• Oil has disadvantage of dissolving rubber or plastic
parts of transducer
• The best coupling agent is a water soluble gel,
available commercially or home made
Coupling agents
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Scan Planes
Sagittal (longitudinal) - divides body into right and
left halves; vertical plane
Transverse - divides body into superior and inferior
halves; horizontal plane
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Sonographic Terminology
Report Features:
 Echogenicity
 Characteristic
 Texture
 Pattern
 Location
 Size/Shape/Number
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Echogenicity
• refers to amplitude level of returning echo
• echo “brightness” directly related to
type and density of the tissue
– echogenic or hyperechoic
• echo producing = bright
– echopenic or hypoechoic
• echo poor = low, dark
– anechoic
• non-echo producing = black
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Characteristic
• Refers to tissue composition
– Cystic = meets all criteria of a cyst
– Complex = cystic and solid components
– Solid = no cystic components
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Criteria of a Cyst
• no internal echoes
• rounded, smooth borders
• good through transmission
(posterior acoustic enhancement)
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• Refers to tissue
“graininess”
 Fine = tissue particles
small, close together
Coarse = tissue particles
large, spaced out
Texture
Breast: Coarse
Thyroid: Fine
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• Refers to uniformity of tissue
Homogeneous
• uniform echoes
• echo level same throughout
structure
Heterogeneous
• non-uniform echoes
• echo level varies in the structure
Pattern
Thyroid: Homogeneous
Thyroid: Heterogeneous
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Location
• Refers to location of structure or mass
relative to adjacent structures
i.e.
“Mass is in right posterior lobe
of liver, adjacent to right renal
superior pole.”
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Size, Shape, Number
 Measure abnormal masses with calipers
 Describe shape of mass/structure --
rounded, lobulated, irregular
 Document or state number of masses
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Obstetric Ultrasound
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• What is Obstetric ultrasound?
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Obstetric ultrasound
• is the application of medical ultrasonography to obstetrics
• used to visualize the embryo or fetus in its mother's uterus
(womb).
• The procedure is a standard part of prenatal care(ANC)
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Preparing to scan
To obtain maximum information from any
obstetric u/s exam, the following three
points should be observed:
1. the u/s equipment should be suited and should
be functioning correctly
2. the woman should be properly prepared
3. you, as a professional, should be confident in
your abilities to perform the exam.
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Obstetric Scans
• For early TAS, bladder should be distended enough to
visualize lower uterine segments
• In case of TVS, bladder should be empty before the
procedure.
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Obstetric Ultrasound
43
Obstetric US is the imaging method of
choice for:
• Dating the pregnancy
• Monitoring fetal growth
• Assessing fetal well-being and
• Evaluating fetal anatomy and maternal pelvic
organs.

Uterus
F. tubes
Ovaries
Bladder
Pelvic Anatomy
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Uterus Anatomy
 Pear shaped organ
 Lies anterior to sigmoid
colon and posterior to
bladder
 Average size: 8 x 5 x 3 cm
 Comprised of 3 layers:
 Serosa
 Myometrium
 Endometrium: is an
important ultrasonographic
structure
 Orientation
 Anteverted , Anteflexed
 Retroverted , Retroflexed
Uterus
Bladder
Pubic
Bone
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46
Myometrium
• mid level echogenic and
transitional zone is hypo
echoic next to endometrium
Endometrium
• highly echogenic strip in
longitudinal and central
echogenic in transverse scans
• thickness depends on the
phase
• throughout the uterus and
cervix
• Seen as a double layer
TA U/S sagittal v. Three layered proliferative
(follicular)phase endometrium ( b/n arrows)
TV U/S sagittal view ---uniformly echogenic
secretary phase endometrium( b/n arrows)

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 Orientation
• long axis of the uterus lies horizontally in sagittal plan at 90
degree with the vagina, anteverted
• The fundus is flexed anteriorly in relation to the cervix with
125 degree, anteflexed
• Retroversion, Retroflexion or combinations makes U/S
visualization difficult in trans abdominal scan but easily seen
in endovaginal ( TVS)

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The uterine fundus may point anteriorly toward the navel, antervertion, or
posteriorly toward the spine, retroversion.

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Fig.3 Transvaginal scan (TV). A demonstrates the transvaginal view of a
normal anteverted uterus seen longitudinally. B shows a similar view of a
normal retroverted uterus. Note that in both cases the body of the uterus is at
right angles to the ultrasound beam.
Fundus of the
uterus Myometrium
Endometrial Stip/line Endometrium wall
thickened
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Fig A. Retroflexed Uterus.
 The uterus is flexed with the fundus (f) directed posteriorly
toward the sacrum on this sagittal midline transbladder image.
 A retroflexed or retroverted uterus may be mistaken for a
pelvic mass on both physical examination and US.
Fig B. Normal
A
B

Adenexal Anatomy
Fallopian Tubes
• Located below fundus
• Average size: 10–12 cm long and 1- 4 mm
in diameter
• Four segments
 Isthmus
 Ampulla
 Infundibulum
 Fimbriae
 Only visible on US when dilated
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 Located anterior and medial to
internal iliac vessels
 Average size: 4 x 3 x 2 cm
 Follicles determined by menstrual
cycle
 Early: 5-11 follicular cysts
 Near Ovulation: dominant follicle 15-
20 mm
• Ovaries
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The Urinary Bladder
 Most anterior structure in pelvis
 Shape is dependant on plane of view as well as volume of
urine contained
 Useful in transabdominal ultrasound as an acoustic window
to visualize the uterus.
A full bladder
displaces bowel from probe and anatomy in question
enhances structures in distal field (acoustic enhancement)
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-There are two stages during normal pregnancy
when it is useful.
These are :-
18- 22 weeks of gestation
32-36 week of gestation
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18- 22 weeks of gestation is best time to :-
-estabilish the gestational age accurately.
-diagnose multiple pregnancy
-diagnose fetal abnormality
-locate placenta and identify patients in whom
there is a risk of placenta previa.
- recognize myoma or any other unexpected
pelvic mass that may interfere with pregnancy
or delivery.
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The other best time is between 32-36 week
of gestation
-to recognize intrauterine growth retardation.
-recognize fetal anomalies that weren’t
detected at first scan.
-locate placenta accurately.
-assess the amniotic fluid and exclude possible
complication.
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First Trimester Ultrasound
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1-Intradecidual Sign(IDSS)
– Has thin echogenic rim around
– Located eccentric to central
echogenic line (endometrial
strip)
– Seen at 4.5wks
– Seen as small >= 2mm
Order of appearance in early pregnancy
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IDSS Pitfalls
• Endometrial fluid collection
• Decidual cyst
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2- Double decidual sac sign ( DDSS)
decidua capsularis
decidua parietalis (vera)
• Seen at 5 wks
• Seen as rounded or oval fluid collection
• Surrounded by two echogenic rings:
- Outer : Decidua
- Inner : Chorion
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 Double Decidual
Sign
 embryo forms
decidua capsularis
and decidua
Vera(decidua
parietalis)
 appears as separate
echogenic layers
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DDSS pitfalls :
• Pseudo gestational sac
 Fluid or blood from tube, accumulate in endometrial
cavity
 Ultrasound appearance: Fluid collection has acute angle
or tear drop shape
Pseudo gestational sac
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3. Yolk Sac
• 2 to 6mm-diameter, spherical, cystic structure.
• Earliest site of blood cell formation in embryo.
• Earliest structure visualized within GS.
• Seen at 5.5wks
• Confirm IUP
• Calcified or thick wall YS is abnormal.
• Number of YS is equal to number of amnions
• Becomes obliterated as amnion fuses with chorion at
14-16wks
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Yolk sac
• Visualization of YS is useful in distinguishing IUP
from pseudo gestational sac
• It should always be visualized in normal
pregnancy in GS:
20-mm mean sac diameter by TAS or
8-mm mean sac diameter by TVS.
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Yolk Sac. The yolk sac (arrow) is seen within the GS by TVS. The normal yolk sac is
less than 6 mm in diameter, spherical, and fluid filled with a thin wall. The yolk sac
is in the fluid space between the thin membrane of the amnion (white arrowhead)
and the chorion (black arrowhead), which defines the limit of fluid within the GS.
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Intrauterine Pregnancy
 Yolk Sac
 First structure seen
within the gestational
sac
 Visible on U/S at 5.5
week GA
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4- Fetal pole and cardiac pulsations
• Fetal Pole visible at
6-6.5 weeks
• Embryo appears
like a little dot on
the YS ( diamond
ring sign )
• Cardiac activity
may be seen as
flickering in this
area.
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5. Amnion
• Seen at closer to 7
weeks
• Thin membrane
surrounding the
embryo.
• The embryo is in the
amniotic cavity.
• The yolk sac is in the
chorionic cavity
A
C
B
A- YS
B- Embryo
C- Amnion
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• The embryo now renamed fetus at 10 weeks
• By the end of first trimester organogenesis will
complete.
• The amnion getting over close to chorion but it does
not fuse until 14-16weeks.
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Summary of order of appearance in early pregnancy
• IDSS
• DDSS
• YS
• FP & Cardiac pulsations
• Amnion
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Mean sac diameter ( MSD)
• Add dimensions of anechoic sac (
excluding echogenic rim)
• ( Length + Height + Width) / 3
• MSD(mm) + 30 = GA ( days)
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Signs of Abnormality
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STAS
•MSD > 20 mm without yolk sac
•MSD > 25 mm without embryo
Strong signs: EVS
MSD › 8 mm without yolk sac
MSD › 16 mm without embryo
The “empty amnion”:
amnion apparent but no embryonic pole

US Characteristics of Normal GS
Intradecidual sign before 5 wks GA
Double decidual sac sign after 5 wks GA (>98% of IUP)
Well-defined round/or oval anechoic sac
Echogenic decidua >2 mm thick
Position in upper uterine body mid way between uterine walls
Growth in MSD >1.2 mm/day
Yolk sac 2 to 6 mm in diameter:
Always present when MSD 20 mm on TAS
Always present when MSD 8 mm on TVS
Embryo:
Always present when MSD 25 mm on TAS
Always present when MSD 16 mm on TVS
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US Characteristics of an Abnormal GS
Major criteria
Absence of yolk sac when:
MSD 20 mm on TAS
MSD 8 mm on TVS
Absence of embryo when:
MSD 25 mm on TAS
MSD 16 mm on TVS
Distorted sac shape
Growth <1 mm MSD/day
Minor criteria
. Irregular sac contour
.Thin decidual reaction <2 mm
.Weak decidual echo amplitude
. Absent double decidual sac sign
.Sac positioned low in the uterus
GSD is measured in three orthogonal planes, and the measurements are averaged to
calculate the mean sac diameter (MSD).
US differentiation of the GS of early IUP from the pseudogestational sac of EP.[1MAJOR or
3MINOR]
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Pregnancy Dating
• Dating the pregnancy and determining the appropriateness of
fetal growth are essential to obstetric care.
• Clinical dating: based on history of the mother's last menstrual
period (LMP) and bimanual assessment of uterine size.
• Sonographic dating: based on measurements of the gestational
sac and the embryo or fetus.
– Serial measurements of fetal parameters are used to
document growth.
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Pregnancy Dating cont’d…
• GA estimates are most accurate in early pregnancy &
become progressively less accurate as pregnancy
advances.
• The composite age, calculated by averaging GA
estimates of multiple parameters, is more accurate than
any single parameter
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• locate the gestational sac, identify the embryo and
record the CRL.
• presence or absence of fetal life should be reported.
• fetal numbers should be documented.
• evaluation of the uterus and adenexal structure
should be performed.
Guidelines for the 1st TM u/s
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First trimester
• Ultrasound assessment of gestational age(GA) has
greater accuracy than physical exam
In the first trimester
• GS mean diameter &
• CRL
measurements have become the primary means of
evaluating GA.
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Gestational sac size
• The gestational sac is an echo-free space containing the fluid,
embryo, and extra embryonic structures.
• is used in the first trimester to estimate GA when no embryo is
visualized.
• The gestational sac diameter is measured in three orthogonal
planes, and the results are averaged.
• The MSD is accurate to within approx 1 wk.
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Look how to measure GS
Gestational Sac
Useful after 4 Wks GA
Sac grows 1 mm/day
Normally round, centrally
located, smooth walled
 yolk sac should be present
when gestational sac > 10
mm
 MSD = L+W+H
3
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Crown-Rump Length
• is measured from the top of the head to the bottom of
the torso of the visualized embryo or fetus.
• The most accurate estimation of GA in early pregnancy
• The primary measure of GA between 6 to 13 weeks
• Provides GA estimations accurate to approximately 0.5
week.
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Crown Rump Length
 Useful after 6WGA
 Fetus grows 1mm/day
 Measure longest
dimension of embryo
 Do not include yolk sac in
measurement
 Exclude extremities
 Embryo should not be flexed
Crown-Rump Length (CRL). The CRL is
measured from the top of the head to the
bottom of the torso (between cursors).
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The longitudinal axis of the fetus using the transabdominal method. The
calipers demonstrate measurement of the crown–rump length.
A correctly performed measurement of CRL is the
most accurate means of estimating the gestational
age.
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Diagnosis of abnormal early
pregnancy
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Diagnoses
• Blighted ovum
• Embryonic death
• Abortion
• Ectopic pregnancy
• GTD
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Blighted Ovum
• Gestational development is arrested
before embryo formed
• Large empty gestational sac
• DDX:
• Early IUP
• Pseudogestational sac (ectopic)
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Blighted Ovum
• Diagnosis
• Compare MSD to presence of a yolk sac or an
embryo
• The “empty amnion”
• Discrepancy between sac size and HCG level
• Abnormal appearance of sac:
• Weak decidual reaction, irregular sac contour,
or distortion of the sac shape
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Diagnoses
• Blighted ovum
• Embryonic death
• Abortion
• GTD
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Embryonic Death
• Absence of cardiac activity when embryonic pole is
visible by TAS
• All embryos of CRL ≥ 7 mm in length should
demonstrate visible cardiac activity.
• If an embryo with a CRL of < 5 mm shows
– no cardiac activity, follow-up ultrasound is
indicated
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Diagnoses
• Blighted ovum
• Embryonic death
• Abortion
• GTD
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 Termination of a pregnancy after, accompanied by,
resulting in, or closely followed by death of embryo or
fetus:
 The deliberate termination of a pregnancy.
 the natural expulsion of a fetus from the womb before
it is able to survive independently.
• Occurs before 20 wks
• 10–15% of all known pregnancies
• 60% of spontaneous abortions – chromosomal
Abortion(miscarriage)
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•Largely a clinical diagnosis
•Types
Threatened abortion– closed cervix
Inevitable abortion– cervical dilatation & fetal or
placental tissue within the cervical os.
Complete abortion– all products of conception have
been expelled
Incomplete abortion – is the expulsion of some, but not
all, of the products of conception
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Missed abortion- the embryo or fetus dies, but the
products of conception are retained in utero.
Septic abortion- occur in infection of the uterus and
sometimes surrounding structures occur.
spontaneous abortion- naturally occurring expulsion of a
nonviable fetus
Habitual abortion – three or more successive spontaneous
abortions.
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Ultrasound diagnosis of miscarriage
• Miscarriage is classified based on the ultrasound
findings as:
 threatened
 missed
 incomplete and
 complete
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Threatened miscarriage
• is usually diagnosed in women with a history of :
 vaginal bleeding and
 in whom a live embryo can be visualized on u/s scan
• In 15% of these women the pregnancy will be lost
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Missed miscarriage
• is defined as retention of a gestational sac within the
uterus following embryonic or early fetal death.
• The diagnosis is usually based on absence of cardiac
activity within fetal pole.
• when embryonic echoes are very small or non-
detectable it is difficult to differentiate b/n a very early
normal pregnancy and a missed miscarriage.
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Fig. A case of missed miscarriage at 8 weeks’
gestation. An irregularly shaped gestation sac is seen
containing a small amniotic cavity (A) with no fetal
pole.
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Complete miscarriage
• is usually diagnosed when endometrium is very thin
and regular.
Ultrasound appearances
 comparable to those of
non-pregnant uterus in
early proliferative phase.
Figure A thin endometrial echo in a woman with a
positive pregnancy test and a history of heavy bleeding is
highly suggestive of complete miscarriage.
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Incomplete miscarriage
Figure A longitudinal section of the uterus showing the uterine cavity, which
contains a large amount of irregular echogenic tissue. This is a typical
ultrasound finding in incomplete miscarriage.
Diagnosis is more controversial
and diagnostic criteria of
endometrial thickness vary b/n 5
and 15 mm.
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Retained products of conception(RPC)
• are usually seen as:
 well-defined area of hyperechoic tissue within
uterine cavity
 blood clots are more irregular.
 Blood clots will be seen sliding within uterine cavity
when pressure is applied on the uterus by TVS.
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Abortion
• Ultrasound findings:
• GS extending into the cervix
• Deformed sac and embryo
• Embryo without cardiac activity
• Intrauterine mass with cystic spaces:
Hydropic degeneration of the placenta
Hydropic villi create a cystic appearance
• Empty uterine cavity
• Serial HCG levels decrease abruptly
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Diagnoses
• Blighted ovum
• Embryonic death
• Abortion
• GTD
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Ectopic Pregnancy
• An ectopic pregnancy is defined as implantation of
fertilized ovum outside uterine cavity.
• 1.4% of all pregnancies
• Increased 6X since 1970 (?PID)
• Causes ~ 1/4 of all maternal deaths
• A total of 93% are tubal
• Abdominal, ovarian, cervical ectopics are rare
• Risk factors:
• Infertility, PID, prior ectopic, H/O tubal surgery
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Ectopic pregnancy locations
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Ectopic pregnancy results if the blastocyst implants anywhere
outside of the uterine cavity.
The vast majority of ectopic pregnancies occur in:
Ampulla Ectopic Pregnancy --- 75% - 93%
Isthmic Ectopic Pregnancy --- 5% - 15%
Heterotopic pregnancy (one embryo in the uterus and one
ectopic embryo): 1/6000
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Ultrasound findings of ectopic pregnancy
• Specific US findings
• Unruptured live ectopic in the adnexa
• Demonstration of an IUP
(coexistent ectopic odds: 1 in 6,000)
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Cornual
Ectopic
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The Exception to the IUP Rule:
Heterotopic Pregnancy
Fig. A case of heterotopic pregnancy.
The lower sac (1) is implanted into the cervix where
the upper sac (2) is normally located within the ute
cavity.
Fig. A longitudinal section of the
uterus
showing a cervical pregnancy (CP)
and empty uterine
cavity above it (C).
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Ectopic Pregnancy
• Strong but not specific US findings
• Adnexal (tubal) ring sign:
• Echogenic trophoblastic tissue lining tube
• PPV is very high ~ 100%
• Large amount of fluid (blood) or
complicated fluid (clot) in cul-de-sac.
PPV ~ 90%
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10/25/2023 118

False-positive diagnosis of an ectopic can result
from
a static loop of bowel
hydrosalpinx
Adhesions or
an endometrioma
10/25/2023 119

Predisposing factors
**Any factor that interferes with normal fallopian tube
function**
Previous tubal surgery
Previous ectopic pregnancy
 Assisted reproductive treatments( in vitro fertilization)
In-utero diethylstilbestrol exposure
Previous gynecologic infections (PID)
Treatment of infertility
Current cigarette smoking
Previous intrauterine device use.
10/25/2023 120

Ectopic pregnancy should always be considered in women of
reproductive age presenting with abdominal pain.
The classic triad of ectopic pregnancy includes abdominal pain,
vaginal bleeding, and amenorrhea.
Transvaginal ultrasound is the modality of choice when diagnosing
an ectopic pregnancy.
 With hCG level> 1500mIU/ mL and no IUP identified on
transvaginal ultrasound, this is high risk for ectopic pregnancy.
Ectopic pregnancy is the leading cause of pregnancy related death
in the first trimester of pregnancy.
Take home points!!!
10/25/2023 121

Diagnoses
• Blighted ovum
• Embryonic death
• Abortion
• GTD
10/25/2023 122

Gestational trophoblastic disease (GTD)
• is a term used for a group of pregnancy-related tumours.
• are rare, and they appear when cells in womb start to
proliferate uncontrollably.
• The cells that form gestational trophoblastic tumours come
from tissue that grows to form placenta during pregnancy.
• In a normal pregnancy, trophoblastic cells aid implantation of
fertilised egg into uterine wall.
But in GTD, they develop into tumour cells.
10/25/2023 123

GTD
 Neoplastic disease of
trophoblast:
. Hydatidiform mole
. Invasive mole
. Choriocarcinoma
 US: Hyperechoic soft tissue
mass filling uterus
 cystic degeneration of
mole
10/25/2023 124

Cause
• Two main risk factors increase the likelihood for the
development of GTD:
1) The woman being under 20 years of age, or over 35 years of
age, and
2) previous GTD
• Although molar pregnancies affect women of all ages,
6x higher risk -women <16 years of age
3x - women >=50 years of age
10/25/2023 126

Hydatidiform mole
Hydatidiform moles are abnormal conceptions with excessive
placental development.
Conception takes place, but placental tissue grows very fast,
rather than supporting the growth of a fetus
Types
1- Complete mole
2- Partial mole
10/25/2023 127

Two Types
Complete mole – classic mole 70%
• dispermic fertilisation of an empty ovum
. involves the entire placenta
. lacks a fetus
. diploid in karyotype
Partial mole (30%)
• dispermic fertilisation of a normal ovum
. involves only a portion of placenta
. an abnormal fetus
. triploid in karyotype
U/S features
. Complete mole – innumerable tiny cysts
“snow storm” appearance
10/25/2023 128

Most common symptoms of GTD
Vaginal bleeding
 enlarged uterus
pelvic pain or discomfort, and
 vomiting too much (hyperemesis)
Malignant forms of GTD are very rare.
About 50% of malignant forms of GTD
develop from a hydatidiform mole.
10/25/2023 129

2nd & 3rd TMs Pregnancy
• Fetal head, body,& extremity measurements
have been commonly used to assess gestational
age(GA).
• Those parameters most commonly measured
include BPD,HC,AC & FL.
10/25/2023 130

• Fetal cardiac activity, number and presentation should
be documented.
• Fetal number ( and chorionicity if multiple pregnancy )
• Basic fetal anatomy
• Amniotic fluid assessment
• Placenta location and appearance and its relationship
to internal cervical os.
• Gestational age assessed
Guidelines for the 2nd& 3rd TM u/s
10/25/2023 131

Dating pregnancy by Ultrasound
• In the second and third trimester pregnancy the
following parameters commonly are used:
 Biparietal diameter ( BPD)
 Head circumference ( HC)
 Abdominal Circumference ( AC) &
 Femoral length ( FL)
10/25/2023 132

Biparietal diameter (BPD)
• is measured on an axial image of fetal head at the
level of third ventricle and thalamus.
• By convention, measurement is made from outer
table of near cranium to inner table of far cranium.
• The measurement is affected by head shape.
10/25/2023 133

BPD
reliable b/n 12-26wk
is distance b/n parietal eminences on either side of
the skull that is widest diameter of skull from side to
side.
10/25/2023 134

Head circumference (HC)
• is the outer perimeter of fetal cranium, measured in
the same plane as BPD.
• The HC measurement is relatively independent of
head shape.
10/25/2023 135

Transthalamic (BPD/HC) Plane.
Axial image of the fetal cranium
demonstrates the paired thalami
(arrowhead) on either side of the
midline third ventricle (long arrow).
The BPD is measured in this plane
from the outer surface of the near
cranium to the inner surface of the
far cranium. The HC is measured in
this same plane as shown.
10/25/2023 136

Abdominal Circumference (AC)
• is the outer perimeter of fetal abdomen
• measured on an axial plane image at the level of
intrahepatic portion of umbilical vein.
10/25/2023 137

Sonographic landmarks for the Abdominal circumference ( AC)
•Circular cross section of the abdomen
• Spine seen on cross section
• Stomach bubble
• Intra-hepatic portion of the portal vein at the level of the portal sinus
• Large sections of fetal ribs seen on each side laterally
• Kidneys not be visualized in the image
10/25/2023 138

AC. The correct plane of measurement of the AC is an axial
plane showing a round abdomen at the level of the umbilical
vein (arrowhead) junction with the left portal vein.
10/25/2023 139

Femur length (FL)
• is measurement of the ossified portion of femoral
diaphysis.
• The entire femur must be imaged
• femoral shaft must be centered in the beam so that
it casts an acoustic shadow.
10/25/2023 140

The FL is the measurement of the ossified portion of
the femoral diaphysis (b/n calipers).
10/25/2023 141

Femoral length
Easily seen after 13 weeks
Reliable measurement in the third trimester
10/25/2023 142

TWIN PREGNANCY
• Incidence: 1% of live births
• TYPES:
– Dizygotic (Fraternal) – 70%
• Always – Dichorionic – Diamniotic(DCDA)
– Monozygotic(Identical) – DCDA,MCDA,MCMA
• During last 10 wks of pregnancy there is a decrease in
growth rate for twin fetuses compared with singleton
fetuses.
10/25/2023 144

Three types of monozygotic twins:
 Dichorionic diamniotic (DCDA) – as in dyzygotic twins but will be
of same sex. ~1/3 of monozygotic twins
 Monochorionic diamniotic (MCDA) – one placenta
~2/3 of monozygotic twins
 Monochorionic monoamniotic (MCMA) –one placenta < 1% of
monozygotic twins
All dyzygotic twins are dichorionic but ~ 60% of monozygotic
twins are monochorionic.
Dyzygotic twins can be same sex or different sex; monozygotic
twins will be same sex.
10/25/2023 145

Ultrasound labeling of twins(Diamniotic)
The position of the two gestation sacs relative to cervix
remains unchanged with gestation
Twin 1 - the twin in the sac
closer to the cervix
Twin 2 - the twin in the sac
further from the cervix
10/25/2023 146

Estimation of GA in twin Pregnancy
 CRL of both fetuses should be measured
 Larger CRL should be used for confirming GA
 NB: GA difference b/n fetuses of >1 Wk in 1st TMP should
be noted & monitored with serial u/s scans.
The discrepancy is often due to:-
constitutional differences
early onset IUGR
structural and/or karyotypic abnormality need to be
excluded
10/25/2023 147

First trimester
• Features supporting a DCDA pregnancy:
 presence of two gestational sacs with a thick echogenic chorion
 a thick inter twin membrane /amnion
 twin peak sign / Lambda sign/Delta sign
 two yolk sacs may be seen (this however does not differentiate a
DCDA pregnancy from a MCDA pregnancy).
• Sonographic assessment of chorionicity is most accurate in the first
trimester after 8 weeks..
10/25/2023 148

Fig. A,B,C are DCDA( Lambda or twin peak sign &
D is MCDA( T-sign)
10/25/2023 149

ESTABLISHING CHORIONICITY AND AMNIONICITY
• The optimal time to distinguish b/n dichorionic,
monochorionic & monoamniotic twin pairs using u/s
is 10 to14 Wks of gestation.
• A dichorional placenta will demonstrate ‘delta’ or
‘lambda’ sign
• A monochorional placenta will demonstrate
‘T sign’ at placental insertion of amniotic membranes
10/25/2023 150

Fig. The ‘delta’ or ‘lambda’ sign
This appearance is diagnostic of a DCDA.
Fig. The ‘T sign’ MCDA twin
pregnancy.
10/25/2023 151

10/25/2023 152

Second trimester
• when there is no placental fusion, two separate
placental sites may be seen
• a finding of two different genders for each twin is a
definitive feature for a dizygotic (DCDA) pregnancy.
10/25/2023 153

Monochorionic twins
• Monozygotic (one egg/identical) twins as a result of when the
fertilized egg divides.
• Monochorionic twins are monozygotic (identical) twins that
share the same placenta.
• Monochorionic twins occur in 0.3% of all pregnancies.
• 75% of monozygotic twin pregnancies are monochorionic;
10/25/2023 154

Fig. Twin pregnancy A- MCDA ( T-sign) & B- MCMA
A B
10/25/2023 155

 The femur continues to grow normally throughout
pregnancy in twin gestations, while the head (BPD and
HC) and abdominal (AC) growth rates decrease in the last
10 wks of pregnancy.
 FL measurement is a more reliable parameter to use
for GA assessment in twin gestations during the 3rd TM.
10/25/2023 156

• COMPLICATIONS:
– DCDA Twins – 10%
 Perinatal mortality
– MCDA Twins – 20%
 Twin-Twin Transfusion syndrome
 Acardia
 Twin embolization syndrome
– MCMA Twins – 50%
• entangled cords
• premature delivery due to severe
polyhydramnios
• conjoined
– craniopagus
– thorachopagus
– omphalopagus
• - Ectopic Twin pregnancy
10/25/2023 157

craniopagus thoracopagus
Anteriorly- commonest
Pyopagus
posteriorly
10/25/2023 158

A genuine multiple gestation Vs Twin sacs due to artifact
Fig. A case of twins at 8 Wks imaged TVS.
Note single chorionic cavity, which contains two
amniotic cavities, confirming this is a case of
MCDA.
Fig. Transverse view of the uterus
obtained TAS, demonstrating lateral
artifact that mimics twin gestation sacs.
10/25/2023 160

Fig. Implantation bleed (arrow) associated
with a singleton pregnancy obtained using TAS
& mimicking a twin gestation.
Fig. A dichorionic twin pregnancy
demonstrating one sac containing a live fetus
(CRL21.4mm) and a dead twin (CRL11.9mm) in
the second sac.
10/25/2023 161

Placenta
The placenta is an organ that
connects the developing fetus to
the uterine wall
Function
 to allow nutrient uptake
waste elimination
gas exchange via the mother's
blood supply
fights against internal infection
and
produces hormones to support
pregnancy.
10/25/2023 162

Sonographic appearance
• Normal placenta is first apparent on US at about 8
wks as a focal thickening at the periphery of the GS.
• The disc like shape of the placenta becomes evident
at 12 wks, and
• At about 18 wks placenta is seen finely granular and
homogeneous, with a smooth covering chorionic
membrane along its fetal surface.
10/25/2023 163

Placental membranes
• consist of an outer layer (chorion) and an inner layer
(amnion).
• These membranes commonly remain separated by a layer of
fluid until 14 to 16 wks GA, when the two membranes fuse.
• The amnion is visualized on US as a thin membrane floating in
fluid.
• The chorion is identified as the membrane that confines fluid
within the GS.
10/25/2023 164

10/25/2023 165

Fig. Normal Placenta
.A TAS scan demonstrates a normal placenta (P) and the insertion site of the cord onto
the placenta (arrowhead).
.The retroplacental complex of veins (arrows) appears as a network of tubular
lucencies beneath the placenta. A, amniotic cavity.
Normal Placenta
 Appears hyperechoic relative
to adjacent myometrium
• Normal size=The normal
placenta has a maximum
thickness of 4 cm and a
minimum thickness of
1 cm.
10/25/2023 166

Placental praevia
• Placental position to the lower segment.
• Before 28 weeks the uterus does not have a true lower
segment.
• Incidence 1:2000; increases with age, multiparity, &
previous C/S , smoking, alcohol ,cocaine use during
pregnancy
• Complications
. 3rd trimester bleeding (90%)
. Premature delivery, fetal or maternal death
. Malpresentation
10/25/2023 169

Types
 low lying pp – within 2cm of internal cervical os.
 Partial pp– partial coverage of cervical os.
 Complete pp– complete coverage of cervical os.
 Marginal pp- when tip of placenta touches
internal Cx os.
10/25/2023 170

10/25/2023 171

Ultrasound confirmation of pp
• Previa can be confirmed with an ultrasound.
• False positives may be due to following reasons:
 Overfilled bladder compressing lower uterine segment
 Myometrial contraction simulating placental tissue in
abnormally low location( Braxton Hicks contraction)
 Early pregnancy low position, which in third trimester may be
entirely normal due to differential growth of the uterus.
10/25/2023 172

FIG. Longitudinal section of the uterus with an
anterior placenta (P). A mass can be seen on
the posterior uterine wall due to a Braxton
Hicks (BH) contraction
10/25/2023 173

ABRUPTIO PLACENTAE
• Premature separation of a normally
positioned placenta from myometrium
• Risk factors:
. Maternal hypertension
. Smoking
. Cocaine abuse
. Previous history of abruption
US:
Specific: retroplacental/ subchorionic
hemorrhage
Suggestive: Placental Thickening
Nonspecific: Placental Hypoechoic areas
10/25/2023 174

Symptoms may include
• Vaginal bleeding
• Abdominal pain
• Uterine contractions that do not relax
• Blood in amniotic fluid
• Nausea
• Thirst
• Faint feeling
• Decreased fetal movements
 The symptoms of placental abruption may resemble other medical
conditions. In this case patients should consult their physicians.
10/25/2023 175

placental abruption
10/25/2023 176

Placenta accreta
occurs when all or part of
placenta attaches abnormally to
myometrium (the muscular layer
of the uterine wall).
Risk factors
placenta previa in the presence
of a uterine scar.
maternal age and multiparity,
other prior uterine surgery,
Uterine irradiation,
leiomyomata & anomalies,
hypertensive disorders of
pregnancy, and smoking.
.
10/25/2023 177

 Three grades of abnormal placental attachment are
defined according to depth of invasion:
• Accreta — chorionic villi attach to myometrium, rather
than being restricted within decidua basalis( 75-78%)
• Increta — chorionic villi invade into the
myometrium.(17%)
• Percreta — chorionic villi invade through the
myometrium.(5%) (invades through entire uterine wall).
10/25/2023 178

Sonographic findings that may be suggestive of placenta accreta
include:
• (1)Loss of normal hypoechoic retroplacental zone( Venous lakes)
• (2)Multiple vascular lacunae (irregular vascular spaces) within
placenta,
• (3)Blood vessels or placental tissue bridging uterine-placental
margin, myometrial-bladder interface, or crossing uterine serosa
• (4)Retroplacental myometrial thickness of <1 mm
10/25/2023 179

Amniotic Fluid
• is essentially a dialysate(part of mixture , soln containing) of
maternal serum in early pregnancy.
• As pregnancy advances, fetal urine becomes the major
source of AF.
• The composition of amniotic fluid is dynamic, with turnover
of the entire volume Q 3hrs.
• The fetus swallows AF at a rate up to 450 ml/24 hrs.
10/25/2023 180

Functions of amniotic fluid
• Amniotic fluid is inhaled and exhaled by the fetus.
• It is essential that fluid be breathed into the lungs in order for them
to develop normally.
• Swallowed AF also creates urine and contributes to the formation
of meconium.
• protects developing baby by cushioning against blows to mother's
abdomen, allowing for easier fetal movement and promoting
muscular/skeletal development.
• AF swallowed by fetus helps in the formation of gastrointestinal
tract.
10/25/2023 181

Amniotic fluid volume
• The amniotic fluid volume increases from
approximately:
 250 ml at 16 weeks to 1000 ml at 34 weeks,
declining thereafter to approximately 800 ml at term.
10/25/2023 182

AMNIOTIC FLUID ASSES’T
Subjective (qualitative )
- Comparing echo free fluid area surrounding the
fetus with space occupied by the fetus
Objective(quantitative)
- assessed by using two measurement methods.
10/25/2023 183

Objective(quantitative)
I- Single deepest pocket measurement
Measuring single deepest amniotic fluid pocket free of
umbilical cord and fetal parts
Single deepest pocket < 2cm Oligohydramnios
> 8cm Polyhydramnios
10/25/2023 184

II- 4 quadrant amniotic fluid index
Divide the gravid uterus into four quadrants
Measure the deepest amniotic fluid pocket of
each quadrant.
Summation results AFI
< 5cm Oligohydramnios and
> 25cm Polyhydramnios
10/25/2023 185

Amniotic Fluid Index(AFI)
10/25/2023 186

OLIGOHYDRAMNIOS
• Abnormally low AFV
. AFI < 5cm.
. Single pocket < 2cm.
Causes:
. PROM
. IUGR
. Renal agenesis
(lack of urine output)
. Fetal death
& post date pregnancy
. Uteroplacental insufficiency
 A major complication of
severe oligohydramnios is
fetal lung immaturity
10/25/2023 187

• Babies with too little amniotic fluid can develop
 contractures of the limbs,
 clubbing of the feet and hands, and
 also develop a life-threatening condition called
hypoplastic lungs
10/25/2023 188

POLYHYDRAMNIOS
• An AFI > 25cm.
. single fluid pocket > 8cm.
. 60% idiopathic
.15–20% related to maternal
diseases (DM, pre-eclampsia,
anemia, obesity)
. 20–25% associated with fetal
anomalies.
10/25/2023 189

Fetuses with polyhydramnios are at risk for a number
of other problems including
-cord prolapse
-placental abruption
-premature birth and
-perinatal death.
10/25/2023 190

Is test to identify compromised fetus
Four parameters assess for Acute hypoxia
1. Reactive fetal heart rate (nonstress test)
2. Respiratory activity (the fetus's ability to move his chest
muscles and diaphragm),
3. Gross motor movements
4. Fetal tone (position of flexion or extension at
rest)
One parameter, the AFV , evaluates for:- Chronic
hypoxia
10/25/2023 191

Criterion Score 2 Score 1 Score 0
Fetal tone
(assessed over 30
min.)
At least 1 motion of limb
and spine from flexion to
extension & back
At least 1 motion of limb
and spine from flexion to
extension
No movements
Fetal movements
(assessed over 30
min.)
3 or more gross body
movements
1 or 2 movements No movements
Breathing
movements
(assessed over 30
min.)
At least one episode of
breathing lasting 60 sec.
At least one episode of
breathing lasting 30- 60
sec.
< 30 s breathing
Amniotic fluid
volume
Largest pocket of fluid
> 2cm in depth
Largest pocket 1-2cm in
vertical depth
Largest pocket of
fluid <1cm in
depth
Fetal heart rate
( assessed over 20
min.)
At least 5 accelerations of
15 bpm, lasting 15 s
2–4 accelerations of, 15
bpm, lasting 15 s
No accelerations
10/25/2023 192

- A variety of different techniques is used for assessment and scoring
 A score of 2 is given for a normal response, and
 A score of 0 is given for an abnormal response
NB- The fetus is at extreme risk for fetal demise with in 1 week with a
total score of 0 or 2 , and
Typically, scores of 6 or below are considered frankly abnormal, and
scores of 7 and 8 are considered suspicious.
- a total score of 8 or 10 is normal
10/25/2023 193

GROWTH ABNORMALITIES
• IUGR(SGA) EFW < 10th pecentile
fetus with intrinsic insults have fixed defects (will not
benefit from early delivery)
• FETAL CAUSES
. CHROMOSOMAL ANOMALIES
. INFECTION (TORCH)
. NORMAL SMALL FETUS
MATERNAL
PRIMARY PLACENTAL INSUFFICIENCY
SECONDARY – HYPERTENTION, NUTRITION, TOXINS
US: EFW + AMF VOLUME + MATERNAL (HPN)
10/25/2023 194

• Fetal macrosomia: > 90th percentile
EFW > 4,000 gm
Complication of macrosomia:
. Shoulder dystocia(difficult in giving birth)
. Perinatal asphyxia(02 deprivation. cause unconscious or
death.)
. Neonatal hypoglycemia
. Meconium aspiration
10/25/2023 195

10/25/2023 196

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