OB exam 3 (2nd & 3rd trimester and measurements)

#1 way to check for fetal viability

heart rate/cardiac motion

how do you rule out placenta previa?

examine the lower uterine segment

what all is measured to assess fetal age?

BPD

head cirucmference

femur length

humerus length

abdominal circumference

HC/AC ratio(abnormal head to abdomen size)

humerus length is usually only found in?

MFM (maternal fetal medicine)

what may not be visualized during 2nd and 3rd trimester on the mother?

ovaries

anatomic survey of the fetus includes which structures and what is it ruling out?

Head, spine, stomach, heart, kidneys and bladder

rules out major congenital malformations

what are you looking for when examining the insertion site of the umbilical cord into the abdomen?

3 vessels- 1 umbilical vein and 2 arteries

human pregnancy length

40 weeks or 280 days beginning from LMP

ovulatory age is approx how long?

38 weeks or 266 days

first trimester

0-12 weeks

2nd trimester

13-26 weeks

3rd trimester

27-40 weeks

Nageles Rule

EDC(estimated date of confinement or due date)= LMP - 3 months +7 days (+1 year)

gravidity

sum of all pregnancies

parity

the number of pregnancies in which the patient has given birth to a fetus at or beyond 20 weeks

Example- define G4P2103

4 total pregnancies

2 full term

1 premature

0 abortions

3 living children

Vertex/cephalic fetal presentation

longitudinal lie- fetal head located at level of bladder and lower uterine segments (head down)

fetal occiput

back of fetal head

Breech fetal presentation

fetal head seen in the fundus

Frank breech

thighs flexed at the hips and lower legs extended in front of head

sometimes the fetus can be turned in this position to ensure safe vaginal delivery

complete breech

both hips and lower extremities are lower than the pelvis, legs crossed

footling breech (incomplete breech)

hips are extended and one or both feet are closest to the cervix-requires C section

transverse lie-what will be seen in a sagittal transducer

a transverse fetus

situs means?

fetal positioning

cranial bones ossify by which week?

12th week

normal brain tissue appears how?

hypoechoic or cystic due to high water content

dura and pia mater appear how?

echogenic

CSF appears how?

cystic

pia later and dura- which one is outer

pia mater=inner most

dura-outermost

brain anatomy and measurements are assessed in which scanning plane?

transverse

as preganancy progresses, why does it become more difficult to visualize the brain?

becasue of increasing calcification of the skill and the position of the fetal head deeper in the pelvis

standard obstetric exam guidelines require you to image and record what structures in the brain?

cerebellum, choroid plexus, cisterna magna, lateral cerebral ventricles, midline falx and the cavum septum pallucidum

why is visualizing the falx important?

because its presence implies that separation of the cerebrum has occured

what can be viewed lateral and parallel to the falx?

deep venous structures (white matter tracts) positioned above lateral ventricles

how does the white matter tracts appear?

2 linear echoes

where is choroid plexus tissue located

within the roof of each ventricle, except at the frontal ventricular horns

the fetal ventricular system consists of:

2 paired lateral ventricles, a midline third ventricle and a fourth ventricle adjacent to the cerebellum

CSF travel path

travels from the lateral to the third ventricle through the foramen of monroe. from the 3rd ventricle, fluid travels through the aqueduct of Sylvius to the fourth ventricle. from there, it flows into the cerebral and spinal subarachnoid spaces from the interventricular foramina and the foramen of Luschka. after this, it is reabsorbed and enters the venous system

picture of CSF pathway

the most common neural tube defects

ventriculomegaly and hydrocephalus

what is associated with spinal defects?

dilation of the entire system, including the fourth ventricle

lumina of the ventricles may be recognized how?

by the bright reflection of their borders and the presence of hyperehcoic choroid plexus tissue that fills the cavity of the ventricles

how do you measure ventricles

from echogenic line to echogenic line

the lateral ventricle is more easily imaged where?

in the distal hemisphere due to reverberation artifact in the near field

body of the choroid plexus is called

gloms

the gloms mark what?

the site at which the ventricles are to be measured

shape of choroid plexus

tear shaped

the glomus should do what in a normal pregnancy?

fill the entire atria

if the body appears to float or dangle, what should be suspected?

ventriculomegaly

ventricular size should do what throughout the gestation?

remain the same

normal measurement of the ventricle

6.5mm

above 10 mm(1cm) is considered abnormal

3rd ventricle cavity is located where?

between the thalamus

how do you find the midline echo complex?

moving the transducer caudally from the ventricles

what is seen in front of the thalamus

CSP

the frontal horns of the ventricles may be seen how?

as 2 diverging echo free structures within the frontal lobes of the brain

what is the band of tissue between the frontal ventricular horns?

the corpus callosum

what are the pulsatile structures bordering the thalamus posteriorly?

the cisterns

what shape are the cerebral peduncles?

heart shaped, but smaller than the thalamus

where can you see the basilar artery pulsations?

between the lobes of the peduncles and the interpeduncular cistern

How does the Circle of WIllis appear?

triangular and highly pulsatile due to cerebral arteries

what is visualized in the center of the circle of willis?

suprasellar cistern

where is the cerebellum located?

in the back of the cerebral peduncles within the posterior fossa

cerebral hemispheres are joined together by what?

the cerebellar vermis

what lies directly behind the cerebellum?

the cisterna magna(posterior fossa)

normal measurement of cisterna magna

3-11 mm, average is 5-6mm

where do you measure the cisterna magna?

from the vermis to the inner skull of occipital bone

linear echoes within the cisterna magna are?

dural folds that attach the falx cerebri

what is the limit for the measurement of cisterna magna?

1 cm

when scanning inferior to or below the cerebellar plane what can be visualized?

the orbits

facial morphology becomes more apparent in what trimester?

2nd trimester

visualization of the fetal face heavily relies on what?

fetal positioning, adequate amounts of amniotic fluid and excellent acoustic windows

the facial profile view shows the contour of what?

the frontal bone, nose, upper and lower lips and the chin

abnormally small chin is called what?

micrognathia

recognized components of down syndrome in the profile view

small nose and midface hypoplasia

coronal facial view demonstrates what?

both orbital rings, parietal bones, ethmoid bones, nasal septum, zygomatic bone, maxillae and mandible

scan obtained in an anterior plane over the orbits demonstrates what?

eyelids and the orbital lens

when is the oral cavity and tongue frequently outlined?

during fetal swallowing

coronal/axial/tangential views on the face demonstrate what? what is it helpful in diagnosing?

nostrils, nares, nasal septum, maxillae and mandible.

diagnoses cleft lip

how are the fetal ears defined?

as lateral protuberances emerging from the parietal bones

the fetal spine is viewed in what scanning planes?

sagittal, coronal and transverse

in sagittal the spine appears how?

as two curvilinear lines extending from the cervical spine to the sacrum

the double line sign from the spine called what?

the railway sign

cervical spine or sacrum is wider?

cervical. it tapers near the sacrum

how does the spine appear in a transverse scan?

as a closed circle

what does the closed circle indicate?

closure of the neural tube

the circle of echoes in the spine represents what?

the center of the verebral body and the posterior elements

when evaluating the spine it is imperative to do what?

to align the transducer in a perpendicular axis to the spinal elements- incorrect angles could falsely indicate an abnormality or not correctly line up with the skin which could indicate spina bifida

posterior elements of the spine

laminae

what serves aas lateral borders to the heart?

the lungs

what should be assessed in the lungs?

lung size, texture, and location to exclude a lung mass

fluid filled lungs seen as?

solid homogeneous masses of tissue bordered by the heart, diaphragm and ribcage

as pregnancy progresses, fetal lung tissue….

appears denser and more echogenic than the liver

what are bony landmarks of the chest cavity?

ribs, scapulae and clavicles

what creates a “washboard” appearance?

echogenic ribs and intercostal space

when should you be able to view the 4 chamber heart?

15 weeks

what degree is the heart positioned in the chest?

45 degrees

which chamber sits closest to the spine and aorta?

left atrium

the apex of the heart points to where?

the left side

what plane does the heart lie in

transverse

left heart valve

mitral valve