Download 4580889cacdb8c500531bd4c9c6e2c7b


 The common tomograms used :
• Axial
• Coronal
• Sagittal (midline)
Fetal biometry

 Fetal growth can be monitored accurately later in life
only if the exact information about the GA is available.
 As less than 50% of women are certain about their
LMP.
1. Menstrual cycle is not 28days long
2. Irregular
3. Taking COC
4. Women had bleed in early pregnancy
5. Lactating women

Gestational age: length of the pregnancy based
upon reliable LMP, assuming that conception occurs
14 days later.
Postmenstrual age: the length of pregnancy based
on the LMP, irrespective of its reliability.


Several US parameters have been used
to estimate GA, the most commonly
used are:
Mean sac diameter
Gestational sac volume
Crown rump length
Biparietal diameter
Femur length
The differ US parameters used to
estimate GA

4-6ws
Mean GC diameter
4-6ws
GS volume
6-12ws
Crown rump length
12-15ws
Defer measurement
15-24ws
BPD, FL, AC
24ws inward
GA cannot accurately
determined by US
Crown rump length

 The biologic variability of CRL is small & growth is
very rapid.
 However there are still a number of factors that can
affect the size of embryo;
1. Measurement errors
2. Different in growth rate between individuals
3. Fetal sex
4. Maternal conditions
5. CRL may indicates an early IUGR.

Tend to underestimate GA by 2-3days
After 12wa CRL m inaccuracy of 7-10days
Crown – rump length

 To establish correct GA :
Unflexed
Longitudinal section
The end point of the crown & rump clearly defined
Placing the calipers correctly on this defined end point.
Crown rump length

CRL between 5-7ws are incorrect:
 The very early embryo is unflexed.
 The full length of the embryo has not been obtained.
 The end point of the embryo is closely adjacent to
yolk sac or wall of GS.
Crown rump length

 After 7ws its easily to identify the end points of the
embryo, but insure that you are imaging the
maximum length of the embryo.
 The CRL should be measured from 3 different
images and the measurements should be agree to
within 3mm in the embryo & 5mm in the fetus.
CRL measurement problems

 Any degree of flexion of fetal spine will produce an
underestimate of CRL when linear calipers are used.
CRL measurement problems

When the fetus remains obstinately
curled, you have 4 choices:
1. Sit and wait.
2. Measure the flexed length using onscreen
nonlinear measuring facilities.
3. Use the linear caliper to measure the parts
of the fetal length that are in straight
sections and add them together.

4-Using a linear calipers along the flexed length.

This is not to be recommended under any
circumstances
How easy to produce errors of 10-15mm simply by
measuring 12-13ws fetus incorrectly

nd
2
trimester biometry–assessing gestational age
2nd trimester biometry –assessing
gestational age

BPD & FL provide the most accurate
assessment of GA.
HC, TCD & AC they provide further
confirmation of GA and aid in the exclusion of
growth related abnormalities.
BPD

 The BPD has traditionally been the most widely used
ultrasound parameter in the estimation of gestational
age
 - A single optimal measurement of the BPD will
predict the gestational age to within ± 5 days.
Biparietal diameter
(BPD)

 BPD : maximum diameter of
transverse section of the fetal
skull at the level of parietal
eminence .
 BPD, OFD & HC can be measured
from:
Lateral ventricles view
Thalami view
Lateral ventricles view of BPD

 A rugby- football- shaped skull, rounded at the back
(occiput) and more pointed at the front (synciput).
 Long midline equidistant from the proximal and
distal skull.
Lateral ventricles view of BPD

 The CSP bisecting the midline 1/3 of the distance
from the synciput to the occiput.
 The two ant horn of lateral ventricles placed about
the midline.
 The two post horn of lateral ventricles placed about
the midline
Lateral ventricles view of BPD

Trans thalamic view of BPD

A rugby- football- shaped skull, rounded at the back
(occiput) and more pointed at the front (synciput).
Short midline equidistant from the proximal and distal
skull
Trans thalamic view of BPD

 The CSP bisecting the midline 1/3 of the distance
from the synciput to the occiput.
 The thalami
 The basal cisterns.

a
b
Measurement

Outer to outer!!!!!
Outer to inner!!!!!!!
Trans cerebellar diameter

Trans cerebellar diameter

It’s a beast dater of pregnancy.
TCD in mm= ws of gestation
until 22ws.

Suboccipitobregmatic view
M. at 90 degree with the longest axis
The bonus with TCD is that it force the
operator to image the entire post fossa which
indirectly refractor of the integrity of neural
tube.
The same plane of nuchal fold thickness.

Measurement of HC

 Short midline, 90 degrees to the beam
 Oval shape
 Thalami
 NO cerebellum or orbits
 Cavum septum pellucidi
 Measure circumference of outer bone (usual to put
calipers at occiput then sinciput)

Abdominal circumference

 The AC is measured in a location that estimates liver
size.
 The liver is the largest organ in the fetal torso, and
its size reflects aberrations of growth, both growth
restriction and macrosomia.


 A circular section of the abdomen ,unbroken & short
rib echo of = size on each side.
 A cross-section of one vertebra visualized as a
triangle of 3 white spots.
 A short length of umbilical vein (1/3 from ant abd
wall to spine).
 The stomach in the left side of the abd.
 NO kidney, bladder, heart. Adrenal allowed

A. This plane is too caudal
B. This is the correct level for AC.
C. this plane is too inclined in a craniocaudal axis.
Femur length

 12ws to term, The upper femur , Full length of femur
 Soft tissue should be visible beyond both ends of the
femur.
 The bone should not appear to emerge with the skin
of the thigh at any point.
Femur length

 The FL measurement is made from the center of the
U shape at each end of the bone.
 Good practice, to obtain measurements from
separate image of the same femur. (1mmof each
other).

Confirming or assigning GA

Assigning GA for the 1st time
in the 2nd trimester

Cephalic index= BPD/OFD=80± 5
Dolichocephaly ( narrow BPD) ,75

Brachycephaly (wide BPD)

Fetal anatomy survey

2nd trimester fetal anatomy

 Intracranial anatomy.
 Nuchal area.
 Fetal spine
 Fetal chest & diaphragm.
 Fetal heart
 Fetal abdomen
 Urinary tract.
 Fetal limbs
 Fetal face.
 Fetal sex
Intracranial anatomy

 Cerebral ventricles
 Thalami & 3rd ventricle
 Cerebellum
 Cisterna magna

Choroid plexus cyst

 <10mm in diameter.
 Unilateral or bilateral.
 Resolve by 26ws
 0.5-2%
Cerebellum

Cisterna magna
Nuchal fold
thickness
2nd or 3rd trimester
Nuchal area

Nuchal translucency
1st trimester
Cystic hygroma
Fetal spine

Lumbar spine, transverse axial
sonogram, 23 weeks. Welldefined ossification of the
laminae (L). C, centrum; arrows,
neurocentral synchondroses.
Chest & diaphragm

Fetal abdomen

 Anterior abdominal wall &Cord insertion
 Major blood vessels
 Gall bladder
 Spleen
 bowel
Anterior abdominal wall

 The integrity of the ant abdominal wall has to be
checked; using the transverse abdominal section.
The insertion of the cord and confirmation of the
presence of 3 vessels should be done.
 Its important as well to visualized the fetal bladder
in the pelvis to exclude extrophy.
Gastrointestinal tract

 The fetal stomach is visible from 9ws inwards as
sonolucent cystic structure in the upper left quadrant
of the abdomen.
 The liver occupies most of the upper abdomen.

 Observe the fetal abdomen
in both cross & longitudinal
section to exclude evidence
of obstruction or area of
increased echogenicity:
Echogenic bowel
Echogenic foci of the liver
The kidneys & urinary
tract

 The kidneys & adrenals, located below the level of
the stomach, on either side and anterior to the spine.
 They are visible from 9ws to 12ws.
The kidneys & urinary
tract

 Its important to assess the size and texture of the
kidneys
 The average kidneys circumference (of the two
together) should be about one third of the abdominal
circumference through the pregnancy.
 They appear slightly hypoechoic when compared
with liver .
 The texture should be mildly heterogeneously
echogenic
The kidneys & urinary
tract

 The fetus empties its bladder every 30-45min
 Renal pelvis Ap. diameter :
 5mm in the 2nd trimester
 10mmin the 2nd trimester
The fetal limbs

Fetal limbs

 The four limbs of the fetus must be visualized.
 This should includes visualization of:
1. long bones: femur, tibia, fibula, humerus, radius &
ulna.
2. Hands &feet.
3. Shape & echogenicity .
4. Relation of the feet to the legs.
Relation of the feet to
the legs.

 When tibia & fibula in longtudenal section only a
cross section of the talus should be seen.
 When the planter or foot
print obtained with the
same section with tibia &
tibia talipes should be
suspected.
 A planter view of the foot
to exclude polydactyl or
syndectyly.
 Look at the position of the
big toe relative to the 2nd to
exclude a sandal gap.

The fetal face

Sagittal plane
Face profile

Transverse plane (orbit, lenses & ocular
biometry)
Coronal & anterior plane
Lips& nostrils
Fetal sex

 Its possible to determine the sex of the fetus trans
abdominally from 14ws but its frequently difficult to
make a definitive diagnosis until 16ws.
 Never guess ; if you are insure, say you do not know.