Normal 2nd/3rd Trimester

when is 2nd/3rd trimester protocol performed

16-22 weeks

why do we do 16 week ultrasound

to coordinate with genetic amniocentesis or mid trimester serum screening

what is done during 20-22 weeks

anatomy and gender

What does EDD stand for?

estimated due date

What does EDC stand for?

estimated date of confinement

What does LMP stand for?

last menstrual period

What is the formula for Naegele's Rule when calculating the EDD?

LMP minus 3 months plus 7 days

Using Naegele's Rule, what is the EDD if the LMP was October 17?

july 24

What is the reverse formula for calculating the LMP when the EDD is known?

EDD plus 3 months minus 7 days

Which three organizations established the guidelines for obstetrical sonography?

ACR, AIUM, and ACOG

What is the main purpose of these guidelines?

to maximize detection of fetal anomalies

What must be documented when evaluating fetal viability?

fetal heart rate

What three things are assessed regarding fetal position and number?

fetal lie, presentation, and number

What fluid measurement and placental information should be evaluated?

AFI and placental location

Which maternal structures should be assessed for pathology?

cervix, uterus, and adnexa

What is fetal biometry?

fetal growth measurements

Name the five major organs specifically listed in the suggested anatomic survey.

brain, four chamber hear, kidneys, stomach, and bladder

Besides the major organs, what other fetal structures should be evaluated?

long bones, spine, and umbilical cord

What facial structures are included in the suggested protocol?

facial profile, nose, and lips

How may fetal brain tissue appear on ultrasound at approximately 12 weeks

hypoechoic or cystic

At what gestational age do the cranial bones ossify, according to the PowerPoint?

12 weeks

At what gestational age are brain tissue texture characteristics determined?

18 weeks

What is the normal contour of the top of the fetal cranium?

round

What is the shape of the cranium near the skull base?

oval

Why can evaluating the fetal cranium be difficult when the fetus is deep in the maternal pelvis?

the view may be limited

Name three techniques that may help improve visualization of the fetal cranium when it is deep in the pelvis.

trendelenburg position, filling the bladder, or EV scanning

What fetal positions are listed as potentially making accurate cranial measurements difficult?

occipitoposterior or occipitoanterior

What does IHF stand for?

interhemispheric fissure

What is another name for the IHF?

falx cerebri

What structure separates the fetal brain into equal hemispheres?

CSP

The presence of the falx cerebri and CSP helps exclude what brain abnormality?

holoprosencephaly

What structures are evaluated above the level of the lateral ventricles?

white matter tracts and venous structures

At what level is the lateral ventricle measured?

body of the choriod plexus

Where is the anteroposterior measurement taken in the lateral ventricle?

at the posterior ventricle

What is the normal lateral ventricular measurement listed in the PowerPoint

6.5mm

What measurement is considered abnormal for the lateral ventricle

>10mm

All three fetal head measurements are obtained from what type of image?

transaxial image

At what anatomical level are the fetal head measurements obtained?

level of the thalami and csp

What is the thalamic view used to measure?

measuring bpd and assessing midline brain strucutres

Why is the thalamic view the proper level for measuring the BPD?

it is the widest transverse diameter of the skull

Where is the cavum septum pellucidum (CSP) located in relation to the thalamus

in front of the thalamus

What is the CSP?

the space between the leaves of the septum pellucidum

The presence of the CSP helps exclude what anomaly?

complete agenesis of the corpus collosum

What structure lies between the thalamic structures?

third ventricle

Where is the cerebellum located in relation to the cerebral hemispheres

behind the cerebral hemispheres

What structure joins the two cerebellar hemispheres together

cerebellar vermis

What may distortion of the cerebellum indicate?

findings suggestive of open spina bifida

What is the banana sign associated with?

arnold chirari malformation

In Arnold-Chiari malformation, what may happen to the cerebellum?

it may be small or displaced downward into the foramen magnum

Why can cerebellar width measurements be useful?

they help assess fetal age when other parameters are comprimised

What is another name for the cisterna magna?

posterior fossa

Where is the cisterna magna located?

directly posterior to the cerebellum

What is the normal measurement range of the cisterna magna?

3-10mm

What is the average measurement of the cisterna magna?

5-6mm

From which two structures is the cisterna magna measured

vermis to the inner skull table of the occipital bone

At what anatomical level is nuchal thickness measured?

at the level of the cisterna magna

According to Filly's Rule, what does it mean if both the atrium of the lateral ventricle and cisterna magna measure 10 mm or less?

it indicates the 95% negative perdictive value of any cns anomaly

What is the negative predictive value stated in Filly's Rule?

95%

What is nuchal thickness?

skin at the back of the scalp/neck, posterior to the cisternna magna and occipital bone

What is the normal nuchal thickness measurement?

less than 6mm

After what gestational age does nuchal thickness become unreliable?

after 20 weeks

What two things should be confirmed when evaluating the fetal orbits

Both orbits/eyes are present and normally spaced

How can orbital width measurements help with fetal assessment?

Gestational age assignment and detection of abnormal orbital spacing

What is anophthalmia?

missing eyes

What is hypotelorism?

Closely spaced or fused eyes

What is hypertelorism?

Abnormally widened spacing between the eyes

What does OOD stand for?

Outer orbital diameter

What does IOD stand for?

Inner orbital diameter

How is the inner orbital diameter measured?

Medial border of one orbit to the opposite medial border

How is the outer orbital diameter measured?

Outermost lateral border of one orbit to the opposite lateral border

What structures are evaluated when examining the fetal facial profile

Frontal bone, nose, upper and lower lips, and chin

Why is the relationship between the nose and lips evaluated?

To evaluate facial formation and identify abnormalities such as cleft lip

What other facial structures should be assessed or verified

Forehead contour, chin formation, and nasal bone

Name the structures that can be seen in the coronal view of the fetal face.

Orbital rings, parietal bones, ethmoid bones, nasal septum, zygomatic bone, maxillae, mandible, upper and lower lips, and nose/lip relationship

What facial abnormality can be evaluated by examining the nose and lip relationship?

cleft lip

Why must fetal hair be excluded from the BPD measurement?

Fetal hair can create peripheral dots around the skull and should not be included in the measurement

In which three scanning planes is the fetal spine evaluated

Sagittal, coronal, and transverse

What is assessed in the sagittal view of the spine

Presence of the spine and skin covering

What is the railway sign?

Two curvilinear lines extending from the cervical spine to the sacrum

What anatomical structures create the railway sign?

Echoes from the anterior and posterior laminae and spinal cord

What does the fetal spine look like in the transverse plane?

A closed circle

What does the closed circle appearance indicate?

Closure of the neural tube

How does the spine change in appearance as it moves toward the sacrum?

It tapers

How does the spine appear near the base of the skull?

It widens

Why is it important to evaluate the integrity of the skin covering the spine?

To check for an intact skin surface

What condition may be present when the skin membrane over the spine is absent?

Open spina bifida

What structures are evaluated when examining the fetal thorax?

Lungs, lateral borders of the heart, and fetal breathing movements

What characteristics should be assessed when examining the lungs?

Size, texture, and location

How do fetal lungs appear later in pregnancy?

They appear denser

Why should displacement of the fetal heart be investigated?

A lung mass may be displacing the heart

How are the ribs evaluated in an oblique section?

Oblique sections show the total length

What do the ribs look like in a sagittal section?

Washboard appearance, echogenic with shadowing and intercostal spaces

What rib characteristic is evaluated in the transverse plane

Curvature

In which plane are the clavicles evaluated?

Coronal

What does the scapula look like in the sagittal plane?

Dense linear echo adjacent to rib shadows

Where is the scapula located in relation to the humeral head in the transverse plane

Medial to the humeral head

How is scapular length evaluated?

Oblique section

How does the sternum appear in the axial plane?

Echogenic structure below the anterior chest skin

What is the standard cardiac view discussed in the PowerPoint?

Four-chamber view

In what plane is the four-chamber heart view obtained?

Transverse