Lecture 1B - OB US Exams

Question 1

First trimester

Answer 1

1-13 weeks

Question 2

Second trimester

Answer 2

14-26 weeks

Question 3

Third trimester

Answer 3

27 weeks until ‘term’ (around 40 weeks)

Question 4

How is pregnancy confirmed

Answer 4

presence of gestational sac. Want it to be intrauterine pregnancy

Question 5

What are we looking for in a gestational sac

Answer 5

Embryo + cardiac activity

Yolk sac

Question 6

What mode is used to confirm fetal HR

Answer 6

M-mode

Question 7

Purpose of first trimester assessment of fetus. Give example

Answer 7

Assess for abnormalities

Increased nuchal translucency measurement (fluid under neck) - chromosomal abnormalities

Question 8

Non-viable pregnancies

Answer 8

Ectopic

Hydatidiform moles

Question 9

Purpose of second trimester assessment (4)

Answer 9

Assessment of viability (cardiac activity)
Fetal number/growth (biometry)
Fetal environment (amniotic fluid, placenta)
Maternal structures (uterus, cervix)

Question 10

Different names for second trimester assessment

Answer 10

Routine
Basic
Level 1
Morphology
Anatomy
Complete
20 week

Question 11

Specialized examination (2)

Answer 11

Level 2

Targeted

Question 12

Indications for level 2 (specialized) examination

Answer 12

Anomaly suspected on level 1
Family Hx
Abnormal blood tst

Question 13

Third trimester assessment

Answer 13

Limited assessment and less common

Question 14

Indications for third trimester assessment (8)

Answer 14

1. Gestational diabetes
2. Maternal measurements inappropriate for gestational age
3. Cannot feel the baby
4. Position check before birth
5. Placental location
6. Incompetent cervix
7. Pathology

Question 15

Transabdo probe

Answer 15

3-5 MHz

Question 16

Transvag probe MHz

Answer 16

5-10 MHz

Question 17

2 non-invasive probes used in later pregnancies

Answer 17

transperineal and translabial (3-5 MHz)

Question 18

ALARA

Answer 18

as low as reasonably achievable

Question 19

Minimizing output intensity (2)

Answer 19

Reducing power settings on machine

Using doppler only as necessary

Question 20

Teratogen

Answer 20

malformaiton of embroy (sound absorbed by heat is a potential)

Question 21

Thermal intex

Answer 21

Measurement of US conditions that can change temp of tissue

Question 22

Thermal index (TI) of 1 means

Answer 22

The tissue may increase in temp 1 degree

Question 23

What is the threshold for potentially hazardous conditions

Answer 23

1.5-2 degrees

Question 24

TI s (soft tissue)

Answer 24

less than 8 weeks

Question 25

TI b (bone)

Answer 25

more than 8 weeks

Question 26

How much can doppler US cause an increase

Answer 26

> 1 degree if held in same spot over 30 sec

Question 27

Mechanical index should be less than

Answer 27

1.9

Question 28

cavitation

Answer 28

Non-thermal bioeffect - creation, oscillation, collapse of bubbles. higher potential in gas-containing structures

Question 29

T/F there are no confirmed bioeffects

Answer 29

true

Question 30

T/F With respect to bioeffects, most human studies have been inconclusive

Answer 30

true