role of ultrasound in obstetrics

Question 1

when is it best to perform an ultrasound to detect trisomies ?

Answer 1

from 10-13 weeks

Question 2

when is it best to perform an ultrasound to detect ectopic pregnancies?

Answer 2

from 5-8 weeks

Question 3

when is a 1st trimesteric ultrasound performed ?

Answer 3

10-13 weeks

Question 4

how can we make an accurate evaluation of gestational age ?

Answer 4

using the crown-rump length

Question 5

what are the indications associated with the bladder when it comes to early pregnancy ultrasound vs early pregnancy trans-vaginal ultrasound ?

Answer 5

early preg abdominal US - full bladder

early preg trans-vaginal US - empty bladder

Question 6

when checking for an ectopic pregnancy what type of ultrasound is used ?

Answer 6

trans-vaginal ultrasound from week 5-8

Question 7

in which disease is trans-vaginal ultrasound a gold standard ?

Answer 7

placenta praevia

Question 8

what is the earliest sign of pregnancy that can be found on ultrasonography ?

Answer 8

gestational sac

Question 9

how early can a gestational sac be seen on ultrasound ?

Answer 9

from 4 to 5 weeks

Question 10

how does a gestational sac differ from a pseudogestational sac ?

Answer 10

gestational sac - has a double ring sign/ double decidual sign
and is intradecidual ( embedded into the endometrium rather than appearing centrally as a pseudogestational sac would)

Question 11

what should you expect after the appearance of a gestational sac ?

Answer 11

appearance of a yolk sac followed by fetal pole followed by cardiac activity

Question 12

when do you expect to see a yolk sac ?

Answer 12

from 5 to 6 weeks or with a b-hcg level of 7000m IU/ml

Question 13

what mainly differentiates a pseudogestational sac from a pseudo sac ?

Answer 13

the yolk sac

Question 14

when do we expect to see a developing embryo ?

Answer 14

at 6-7 weeks

Question 15

at what CRL length is a heart beat or a pulse seen ?

Answer 15

at 5mm vaginally

Question 16

what is the most common cause of embryonic death ?

Answer 16

chromosomal abnormality

Question 17

when do we consider a pregnancy non-viable on trans-vaginal ultrasound

Answer 17

if there is no fetal heart rate whilst having a CRTL of more than 7
or
if there is no fetal pole where the MSD is more than 25 mm with no embryo

Question 18

by how much are the fetus and gestational sac expected to grow per day ?

Answer 18

1 mm

Question 19

what is the discriminatory zone of b-hcg ?

Answer 19

relies on BHCG increasing by more than 66% in 48 hours if not and there is no bleeding and the uterus is empty
consider ectopic pregnancy

Question 20

what is a blighted ovum ?

Answer 20

a blighted ovum or an anembryonic sac is intra decidual but has reached a diameter of 25 or more with no yolk or fetal pole

Question 21

what is the best thing to do if you are not sure if the sac is anembryonic or not ?

Answer 21

repeat in a week

Question 22

what does a molar pregnancy look like on ultrasound ?

Answer 22

snow storm appearance

Question 23

what is commonly found in the ovaries in association with molar pregnancies ?

Answer 23

theca lutein cysts , secondary to BHCG

Question 24

which type of ultrasound is used to detect a gestational sac ?

Answer 24

trans-vaginal ultrasound

Question 25

before the formation of the placenta how does exchange between the embryo and the mother happen ?

Answer 25

through the yolk sac

Question 26

what is the natural course of the yolk sac ?

Answer 26

yolk sac disappears and is sonographically undetectable by week 14

Question 27

what is the earliest sign of a polyamniotic pregnancy ?

Answer 27

multiple yolk sacs

Question 28

when is the CRL measurement made ?

Answer 28

between 7 to 13 weeks

Question 29

what are the second trimesteric biometric measurements ?

Answer 29

bi-parietal 
occipito-frontal diameter 
head circumference
abdominal circumference 
femur length

Question 30

how can we monitor growth of long bones ?

Answer 30

femur length

Question 31

which part of the femur is used for measurement of the femur length ?

Answer 31

entire diaphysis without the epiphysis

Question 32

what is the most important function of measuring FL?

Answer 32

excluding dwarfism

Question 33

what is the most important measurement to take in late pregnancy ?

Answer 33

abdominal circumference

Question 34

when is the fetal biophysical profile assessed ?

Answer 34

third trimester

Question 35

how can fetal death be confirmed ?

Answer 35

absence of cardiac activity for at least 2 to 3 minutes , which should ideally be confirmed by 2 or more examiners

Question 36

what is the most ideal time to determine fetal sex ?

Answer 36

17-20 weeks

Question 37

what are the components of biophysical profile ?

Answer 37

fetal breathing movement 
fetal tone 
fetal movement 
amniotic fluid volume 
non-stress test

Question 38

what is the modified BPP ?

Answer 38

combines the non stress test with amniotic fluid assessment

Question 39

what three blood vessels are assessed using doppler ?

Answer 39

umbilical artery
middle cerebral artery
ductus venosus

Question 40

which of the three arteries can be used to decide the timing of delivery ?

Answer 40

ductus venosus

Question 41

how is liquor assessed ?

Answer 41

measure the dimensions of the largest vertical pocket of amniotic fluid

Question 42

which measure is the most accurate measure of amniotic fluid ?

Answer 42

amniotic fluid index

Question 43

how is the amniotic fluid index measured ?

Answer 43

uterus is divided into four quadrants and sum of all four measurements are taken