TOG: Role of Ultrasound in Early Pregnancy Problems

Question 1

what are the key USS measurements in early pregnancy?

Answer 1

CRL (crown rump length), MSD (mean sac diameter)

Question 2

How is mean sac diameter measured on USS? How does it appear on USS?

Answer 2

measure the inner borders of the sac. Hypoechoic round structure with echogenic rim. Situated eccentrically within decidua, at/near uterine fundus.

Question 3

how many days from LMP is the gestation sac and crown rump length visualised on USS?

Answer 3

MSD= 28-31 days from LMP
CRL= day 35

Question 4

after what gestation are CRL measurements less reliable?

Answer 4

14 weeks

Question 5

what are the ultrasound features that increase the suspicion of likely pregnancy failure?

Answer 5

subchorionic haematoma,
small gestational sac for gestation,
enlarged yolk sac

Question 6

Serial HCG levels are done if pregnancy not seen on USS. What percentage of these cases are found to be ectopic pregnancy?

Answer 6

6%

Question 7

in what percentage of women are there NO identifiable risk factors for ectopic?

Answer 7

50%

Question 8

What are the recognised risk factors for ectopic pregnancy?

Answer 8

smoking, PID, previous ectopic, assisted reproductive treatment, previous tubal surgery

Question 9

what percentage of ectopic pregnancies are tubal?

Answer 9

> 90%

Question 10

what percentage of tubal pregnancies are diagnosed using TVS at the time of presentation?
What percentage are diagnosed on follow up scans?

Answer 10

> 70%- at first presentation

90% on follow up scan

Question 11

what is an interstitial ectopic pregnancy?

What percentage of ectopics are interstitial?

Answer 11

implantation in the interstitial portion of fallopian tube (where the tube meets uterus)

1-6% ectopics are interstitial

Question 12

what is the “interstitial sign” seen on USS with interstitial ectopic pregnancies? What is its sensitivity / specificity?

Answer 12

interstitial sign= visualising thin echogenic line of the endometrial cavity and following this along to the periphery of the interstitial sac.
This sign has sensitivity= 80%, specificity =98%

Question 13

what type of USS scan is ideally suited for interstitial ectopics?

Answer 13

3D USS in coronal view- to view the interstitial segment of the tube

Question 14

what are the USS criteria for cervical pregnancy?

Answer 14

empty uterus
barrel shaped cx
gest sac/ trophoblastic mass below level of internal os
negative ‘sliding sign’
sustained peri-trophoblastic circulation on colour doppler

Question 15

what are the criteria used to diagnose caesarean section scar pregnancy?

Answer 15

1. location outside uterine cavity
2. pregnancy implanted into deficient scar with gest sacpartially/ fully located in myometrial mantle
3. sustained peri-trophoblastic flow on colour doppler

Question 16

which USS sign is helpful in distinguishing a miscarriage from cervical ectopic or c/s scar ectopic?

Answer 16

‘sliding sign’

Question 17

heterotopic pregnancy is mostly associated with what type of pregnancies?

Answer 17

pregnancies in which assisted reproductive techniques used

Question 18

what percentage of women being classified with PUL turn out to be ectopic?

Answer 18

7-30%

Question 19

what is the positive predictive value and sensitivity of USS in the diagnosis of molar preg?

Answer 19

positive predictive value= 48%
sensitivity =44%
Difficulty arises in differentiating between hydropic changes in miscarriage and molar change

Question 20

If there has been a >13% decrease in serial bHCG, what is likely diagnosis and f/u

Answer 20

likely diagnosis = failed PUL

f/u= UPT in 2 weeks, repeat hCG if UPT +ve

Question 21

if there has been >66% increase in serial bHCG measurement, what is likely diagnosis and f/u

Answer 21

likely diagnosis = normal intrauterine preg

f/u= repeat TVS on day 7

Question 22

if there has been a <66% increase in serial bHCG level, what is likely diagnosis and f/u?

Answer 22

diagnosis= probable ectopic.
f/u= rpt TVS on day 7 or when bHCG expected to be >1000

Question 23

if there has been <13% decrease in serial bHCG levels, what is likely diagnosis and f/u?

Answer 23

diagnosis= failed PUL or ectopic
f/u= repeat serum HCG on day 7