Second & Third Trimesters

What is the protocol for second and third trimester sonography?

1. fetal viability

2. fetal presentation

3. fetal number (anatomy/growth of each, placenta, membranes, AFI, etc.)

4. amniotic fluid index

5. evaluate placenta grade, location, relationship to cervical os

6. cervical length

7. fetal age

8. evaluation of uterus, adnexa, cervix

9. 3VC

10. gender

11. establish systematic protocol

What are growth parameters for assessing fetal age?

- BPD

- head circumference (HC)

- femur length (FC)

- humerus length

- abdominal circumference (AC)

- HC/AC ratio (head to abdomen size)

What does abdominal circumference measure?

fetal weight

What is typically not seen in second and third trimesters?

ovaries

What is included in a fetal anatomic survey?

head

spine

stomach

heart

kidneys/bladder

What is 3VC?

umbilical cord insertion into abdomen and placenta (2 arteries, 1 vein)

When is the gender of fetus medically indicated?

with multiple gestations

A human pregnancy lasts around __ weeks beginning from the LMP

40

Ovulatory age pregnancy lasts around __ weeks

38

An unknown LMP requires an ultrasound for ___, aka ___

EDC; EDD

(estimated date of confinement/delivery)

First trimester = ___ weeks

Second trimester = ___ weeks

Third trimester = ___ weeks

0-12

13-26

27-40

Post-term pregnancy is greater than __ weeks

40

What is the equation for estimated delivery date called?

nagele's rule

What is the equation for estimated delivery date?

EDD = LMP - 3 months + 7 days (+ 1 year)

What is EDD of an LMP of 3/17/2012?

12/24/2012

What is gravidity?

number of all pregnancies

(includes abortion, ectopic, stillbirths)

What is parity?

number of births to a fetus at or beyond 20 weeks

(includes full-term, premature, abortions, living)

G4P2103 describes what?

4 gravidity

2 parity

1 premature

0 abortions

3 living children

Fetal presentation determines the position of the fetus in relation to the position of the ___

mother

After fetal position is understood, determine the ___ and ___

direction; orientation

What are the fetal positions?

vertex/cephalic

breech

transverse

In a vertex/cephalic position, the fetal head is located at level of the ___ and ___

bladder; lower uterine segment

In a vertex/cephalic position, the fetal body is in the ___

uterine fundus

In a breech position, the fetal body/lower extremities are in the ___

lower uterine segment

In a breech position, the fetal head is seen in the ___

uterine fundus

Frank breech is when fetal thighs are flexed at the ___ and the lower legs are extended ___ the head

hips; in front of

Complete breech is when fetal hips and lower extremities are ___ than the pelvis and legs are ___

lower; crossed

Footling breech is when fetal hips are ___ and one or both feet are closest to the ___

extended; cervix

What is footling breech also called?

incomplete breech

What breech position can be turned?

frank breech

What breech position requires a c-section?

footling/incomplete breech

Breech positions on ultrasound

What is a transverse fetus position?

fetus lies across uterus

In a transverse fetal position, a sagittal transducer will show a ___ fetus

transverse

In a transverse fetal position, a transverse transducer will show a ___ fetus

sagittal

When labeling twin fetuses, twin A will always be closest to the ___

cervix

What is situs?

positional arrangement of a fetus's organs (right vs left sides)

The right and left sides of the fetus are determined by identifying ___

landmarks

Review fetal presentation (slides 20-22)

Fetal brain tissue may appear ___ or ___

hypoechoic; cystic

When do fetal cranial bones ossify?

12 weeks

The dura mater and pia mater within the fetal cranium appear ___

echogenic

CSF within the fetal cranium appears ___

cystic

What scanning plane are fetal brain anatomy and measurements assessed in?

transverse

Why is the fetal cranium difficult to evaluate in the late third trimester?

bc of deep pelvic positioning

At the most cephalad (upper) level, the contour of the fetal skull should be ___ with a ___ surface

oval; smooth

What is the interhemispheric fissure / falx?

membrane separating the fetal brain into right and left hemispheres

At the most cephalad level within the fetal skull, the falx should be ____

continuous

___ and ___ to the falx, two linear echoes representing deep venous structures (white matter tracts) are viewed

lateral; parallel

White-matter tracts are positioned ___ the lateral ventricles

above

What ventricles are in the fetal ventricular system?

2 lateral ventricles

3rd ventricle

4th ventricle

The ventricles are filled with ___ produced by the ___

CSF; choroid plexus

Choroid plexuses are located within the ___ of each ventricle

roofs

What is the flow of CSF?

lateral ventricle

foramen of Monroe

3rd ventricle

aqueduct of Sylvius

4th ventricle

foramina of Luschka

cerebral and spinal subarachnoid spaces

venous system

What is one of the most common fetal neural tube defects?

ventriculomegaly

(enlarged ventricles)

Lateral borders of the ventricular chambers are seen as ___ lines coursing ___ to the falx

echogenic; parallel

At ___ weeks gestation, the lateral borders appear to be large in relationship to the developing ___ ___; moves more ___ later in pregnancy

12-22; cranial hemispheres; medial

The body (glomus) of the choroid plexus marks the site at which the ___ are measured

ventricles

If the glomus of the choroid plexus appears to float or dangle within the ventricular cavity, ___ may be present

ventriculomegaly

Does ventricular size vary throughout gestation?

no - it remains the same

How do you measure fetal ventricles?

place calipers at junction of ventricular wall and lumen of ventricle (inner to inner)

What is normal ventricular measurement?

6.5 mm

Abnormal ventricular measurement is above ___

10 mm (1 cm)

What part of the skull do you measure BPD?

midline echo complex

How do you find midline echo complex on ultrasound?

move the transducer caudally from lateral ventricles

When measuring BPD, paired ___ will be seen on either side

thalamus

When measuring BPD, what is located between the thalamus?

3rd ventricle

When measuring BPD, what is seen in front of the thalamus?

cavum septum pellucidum (CSP)

At the midline echo complex, frontal horns of the lateral ventricles may be seen as ___ ___ ___ structures within the ___ ___ of the brain

2 diverging echo-free; frontal lobes

What is the corpus callosum?

band of tissue between the frontal ventricular horns

The corpus callosum is ___ sonographically

ill-defined

The cisterns are ___ structures bordering the thalamus ___

pulsatile; posteriorly

Moving transducer more caudally from midline, what heart-shaped structures smaller than the thalamus are visualized?

cerebral peduncles

Moving transducer more caudally from midline, ___ artery pulsations can be seen

basilar

Moving transducer more caudally, the circle of Willis may be seen ___ to the midbrain and appears ___ and highly pulsatile because of ___

anterior; triangular; cerebral arteries

What may be visualized in the center of the circle of Willis?

suprasellar cistern

The cerebellum is located ___ to the cerebral peduncles, within the ___

posteriorly; posterior fossa

The cerebellar hemispheres are joined together by the ___

cerebellar vermis

The ___ lies directly behind the cerebellum

cisterna magna / posterior fossa

Normal cisterna magna measures ___; and averages ___

3-10 mm; 5-6 mm

When measuring cisterna magna, measure from the ___ to the inner ___ bone

vermis; occipital

Within the cisterna magna space, ___ can be seen as linear echoes within

dural folds

When scanning inferior to the cerebellar plane, what may be visualized?

orbits

When scanning fetal facial profile, what should you assess?

frontal bone

nose

lips

chin

Fetal facial profile determines the relationship of the ___ and ___ and assesses the formation of the ___

nose; lips; chin

What does a coronal facial view demonstrate?

both orbital rings

parietal bones

ethmoid bones

nasal septum

zygomatic bone

maxillae

mandible

The coronal facial view is scanned in the anterior plane over the orbits to demonstrate the ___ and the ___

eyelids; orbital lens

In a coronal facial view, what is frequently outlined during fetal swallowing?

oral cavity and tongue

What do tangential views demonstrate?

nostrils/nares

nasal septum

maxillae

mandible

What view is helpful in diagnosing a cleft lip?

coronal facial view

Ears may be defined as ___ protuberances emerging from the ___ bones

lateral; parietal

Fetal hair is often observed along the ___ of the skull; not to be included in the ___

periphery; BPD measurement

What scanning planes is the vertebral column evaluated in?

sagittal

coronal

transverse

In sagittal, the spine appears as ___ extending from the ___ to the ___

2 curvilinear lines; cervical spine; sacral spine

The cervical spine is ___ than the sacrum

wider

The normal fetal spine tapers near the sacrum and widens near the base of the skull. This double-line appearance of the spine is referred to as the ___ sign

railway

In transverse, the spinal column appears as a closed ___, indicating closure of the ___

circle; neural tube

The circle of echoes in transverse represents the center of the ___ and the ___

vertebral body; posterior elements

When evaluating the spine, it is important for the sonographer to align the transducer in a ___ axis to the spinal elements so that any interruption of skin surface can be detected

perpendicular

Lungs serve as ___ borders for the fetal heart

lateral