Lecture 4A - Normal First Trimester (Early)

Question 1

what do you assess for a dating scan? (3)

Answer 1

gestational sac (presence, #, size, GA)
embryo (size + cardiac activity)
maternal structures

Question 2

dating scan occurs during what week range

Answer 2

0-13 weeks

Question 3

patient history questions (6)

Answer 3

Full bladder
LMP
positive pregnancy 
medication
irregular bleeding

Question 4

embryonic structures that slowly become visible (4)

Answer 4

JAMAL

Question 5

when does implantation occur

Answer 5

day 20-23

Question 6

what is the first (non-diagnostic) sign

Answer 6

focal echogenic thickening on one side of endo

Question 7

when youre looking at the gestational sac, what are you looking at?

Answer 7

chorionic cavity

Question 8

when is the GS visible

Answer 8

4.5-5 weeks

Question 9

what is IDSS

Answer 9

intradecidual sac sign - GS seen WITHIN decidua

Question 10

IDSS should be differentiated from (2)

Answer 10

pseudogestational sac

decidual cysts

Question 11

what confirms intrauterine pregnancy

Answer 11

double decidual sac sign

Question 12

what is the DDSS comprised of?

Answer 12

double concentric rings around GS (parietalis outer, capsularis inner)

Question 13

what does mean sac diameter calculate? what is the formula? how do you measure?

Answer 13

gestational age
MSD = (LWH)/3
INNER TO INNER

Question 14

yolk sac functions (4)

Answer 14

• nutrients
• protein production
• hematopoiesis
• vitelline ducts (connects yolk sac to embryo)

Question 15

what does the balloon on string represent

Answer 15

yolk sac + vitelline ducts

Question 16

what is the most accurate measure of GA?

Answer 16

crown rump length, main measurement in 1st trimester

Question 17

what is the first organ to function?

Answer 17

heart

Question 18

what mode to assess fetal heart rate

Answer 18

M mode

Question 19

amnion fuses with walls of

Answer 19

gestational sac (chorion)

Question 20

double bleb sign includes (3)

Answer 20

YS
Embryo
Amniotic sac

Question 21

where does the amniotic fluid come from? in 1st and 2nd trimester

Answer 21

1st trimester placenta

2nd trimester urine

Question 22

what are the important 1st trimester (early) measurements you must take (4)

Answer 22

• MSD
• yolk sac
• fetal pole (CRL)
• fetal HR

Question 23

what should the yolk sac measurement be under in early first trimester

Answer 23

<5.6 mm

Question 24

when is the first trimester scan

Answer 24

11-14 weeks