OB (Early 1st Trimester Sono Appearance)

Question 1

What weeks is the 1st trimester?

Answer 1

0-13 weeks

Question 2

What do we scan in the 1st trimester assessment?

Answer 2

Gestational Sac:

• presence (confirm IUP)
• #
• size (gestational age)

Embryo:

• size (gestational age)
• cardiac activity

Maternal Structures:

• uterus, cervix, ovaries and adnexa
• fibroids, cysts, ectopic pregnancies, molar pregnancies, etc.

Question 3

Patient Prep.

Answer 3

• no fasting
• full badder (transabdo)
• empty bladder (transvag)

Question 4

Questions to Ask

Answer 4

• positive pregnancy test
• LMP
• gravidity, parity, abortus
• pain or bleeding
• medications
• previous C section
• complications with previous pregnancies

Question 5

What order do embryonic structures become visible?

Answer 5

1) decimal reaction
2) gestational sac
3) yolk sac
4) embryo

Question 6

What days does implantation occur?

Answer 6

-20 to 23

Question 7

How big is the conceptus at the end of implantation?

Answer 7

• 0.1mm

- not visible

Question 8

What is the 1st reliable sign of an intrauterine pregnancy?

Answer 8

-gestational sac

Question 9

When is the visible gestational sac visible?

Answer 9

• 4.5 to 5 weeks

- once the mean sac diameter reaches 2 to 3 mm

Question 10

Where is the gestational sac seen?

Answer 10

• within decide

- intradecidual sac sign (IDSS)

Question 11

What must we differentiate the GS from?

Answer 11

• pseudogestational sac

- decidual cysts

Question 12

Pseudogestational Sac

Answer 12

• sm amount of fluid in endometrial cavity

- between endometrial layers

Question 13

Decidual Cysts

Answer 13

-sm cysts that can form within decimal reaction

Question 14

A true gestational sac will be…

Answer 14

• round/oval
• eccentric
• directly adjacent to endometrial lining
• develop a yolk sac and embryo
• develops a double decidual sac sign

Question 15

Double Decidual Sac Sign (DDSS)

Answer 15

• confirms intrauterine pregnancy
• 2 concentric rings surrounding gestational sac
• consists of decide parietals and decide capsularis
• can differentiate abevbryonic pole and embryonic pole (site of future placental development)

Question 16

Mean Sac Diameter (MSD)

Answer 16

• common mode of measurement
• 3 perpendicular planes
• inner to inner (only fluid/anechoic part)

MSD= (L+W+H)/3

Question 17

What weeks can MSD be used?

Answer 17

-5 to 10

Question 18

How much does the gestational sac grow a day?

Answer 18

-1mm

Question 19

How many weeks if the MSD is 2mm?

Answer 19

-GA= 4 to 4.5 weeks

Question 20

How many weeks if the MSK is 5mm?

Answer 20

-GA= 5 weeks

Question 21

What appears at 5.5 weeks?

Answer 21

-YS

Question 22

What appears at 6 weeks?

Answer 22

-embryo adjacent to YS

Question 23

Yolk sac is resent is MSD = ___mm.

Answer 23

8 (TV)

Question 24

Embryo is present is MSD = ___mm.

Answer 24

16 (TV)

Question 25

What does visualization of YS help to confirm?

Answer 25

-true GS

Question 26

How do we measure the YS?

Answer 26

-inner to inner (usually circular)

Question 27

How big is the YS when we 1st image?

Answer 27

-2.3mm (+1mm/day)

Question 28

What is the max diameter of the YS?

Answer 28

-5.6mm (10 weeks)

Question 29

What is associated with a lg YS?

Answer 29

-pathologies

Question 30

Functions of YS?

Answer 30

- nutrients to embryo - vitelline duct (arteries and veins) connect YS to embryo - produces albumin, alphafetoprotein (AFP) and other proteins - embryonic hematopoiesis (formation of blood cells)

Question 31

Where does hematopoesis continue to in the 8th week?

Answer 31

- liver - spleen - bone marrow - lymph nodes

Question 32

Why does the YS stop functioning?

Answer 32

-when the placenta takes over

Question 33

What week is the embryo/fetal pole?

Answer 33

-6 to 10

Question 34

Where does the embryo appear at week 6?

Answer 34

- adjacent to YS | - appears as focal thickening

Question 35

Embryo is present is MSD = ___mm. (TA)

Answer 35

16

Question 36

Embryo is present if MSD = ___mm. (TA)

Answer 36

25

Question 37

How many mm is the embryo when 1st visualized?

Answer 37

-2 to 4 mm

Question 38

Crown-Rump Measurement (CRL)

Answer 38

- main measurement used in 1st trimester - most accurate estimate of GA - correlated with OB charts for GA - can be seen at 7 to 8 weeks - do not include YS or extremities

Question 39

What measurements are done in 2nd trimester?

Answer 39

- BPD - HC - AC - FL **less accurate than CRL (1st trimester)

Question 40

When can the embryo's limb buds be seen?

Answer 40

-8 to 9 weeks

Question 41

When can we see the embryo moving?

Answer 41

-9 to 10 weeks

Question 42

What is the 1st organ to function in the embryo?

Answer 42

- primitive (tubular) heart | - 5 weeks (36 to 37 days)

Question 43

When can cardiac activity been seen on an embryo?

Answer 43

>5mm (TV)

Question 44

Cardiac activity must been seen if fetal pole = ___mm.

Answer 44

7

Question 45

Double Bleb Sign

Answer 45

-appearance of amniotic sac, YS and embryo between them

Question 46

Umbilical Cord

Answer 46

- can been seen @ end of 6th week (CRL= 4mm) - 2 umbilical arteries - 1 umbilical vein - the allantois

Question 47

Which trimester is the umbilical cord better seen in?

Answer 47

-2nd

Question 48

Allantois (2)

Answer 48

- closely associated with umbilical cord - part of connecting stalk - contains liquid waste early in pregnancy

Question 49

Vitelline Duct

Answer 49

- closely associated with umbilical cord (not within cord) - aka omphalomeseneric duct - aka yolk stalk