ERU 23- The First Trimester

Question 1

Zygote > Morula > blastocyst

Answer 1

Blastocyst:
Outer trophoblastic cells (produce hcg) > placenta and chorion
Inner part > embryo, amnion, cord, yolk sacs

Question 2

Chorionic sac/gestational sac: outer
Amniotic sac: inner membrane
Chorionic cavity/extraembryonic coelom: secondary yok sac between these membranes

Question 3

At what hcg level should a gestational sac be visible on TVUS? (What is the discriminatory zone?)

Answer 3

1,000 - 2,000

Question 4

During what week of pregnancy does the decidual reaction occur?

Answer 4

Weeks 3-4

Question 5

At what gestational age does a gestational sac appear?

Answer 5

Weeks 4-5

Question 6

chorionic cavity

Answer 6

The space between the gestational sac and the amniotic sac. The location of the secondary yolk sac

Question 7

Chorion frondosum

Answer 7

The decidualized tissue at the implantationsite containing the chorionic villi. The fetal contribution to the placenta

Question 8

Chorionic laeve

Answer 8

The portion of the chorion that does not contain chorionic villi

Question 9

chorionic villi

Answer 9

Fingerlike extensionof the trophoblastic tissue that invades the decidualized endometrium

Question 10

decidua vasalis

Answer 10

the endometrial tissue at the implantation site.

The maternal contrivution of the placenta

Question 11

Decidua capsularis

Answer 11

The portion of the decidua opposite the uterine cavity, across from the decidua basalis

Question 12

decidua parietalis (vera)

Answer 12

The decidualized tissue along the uterine cavity adjacent to the decidua basalis.

Question 13

How is the mean sac diameter used to calculate early dating?

Answer 13

MSD + 30 + GA in days

Question 14

At what gestational age does the yolk sac appear?

What does the yolk sac produce?

Answer 14

5.5 weeks

AFP: important for hematopoiesis

Question 15

What connects the embryo to the yolk sac?

Answer 15

The vitelline duct, which contains one artery and one vein

Question 16

What is contained in the chorionic cavity?

The amniotic cavity?

Answer 16

Yolk sac and fluid

Amniotic fluid and embryo

Question 17

At what gestational age are limb buds seen?

Answer 17

7-8 weeks

Question 18

What is the cystic structure that can be seen in the fetal head at 7-8 weeks?

Answer 18

Rhombencephalon/Hindbrain: eventual 4th ventricle

Question 19

At what gestational age does physiologic bowel herniation occur?

Answer 19

8-12 weeks.

Question 20

What maternal and fetal layers form the placenta?

Answer 20

Maternal decidua basalis and fetal chorion frondosum

Question 21

When is Nuchal Translucency measured?

What is a normal result?

Answer 21

11 - 13+6 weeks (when CRL is 45-84mm)

3-3.5mm

Question 22

What criteria would define nonviable pregnancy in the first trimester?

Answer 22

Question 23

Intradecidual sign

Answer 23

The sonographic presence of a small gestational sac within the decidua at approximately 4 to 4 and 1/2 Weeks with a mean sac diameter of approximately 2.5 mm. The first sonographic sign of pregnancy.

Question 24

Double bleb sign / double decidual sac sign

Answer 24

Early amniotic sac with yolk sac. Present by 5.5 to 6 weeks

Question 25

A rare form of gestational trophoblastic disease in which molar tissue invades the myometrium or adjacent anatomic structures

Answer 25

Chorioadenoma destruens

Question 26

What is the most common cause of a single umbilical artery?

Answer 26

Secondary atrophy of a previously normal vessel

Question 27

How is gestational age calculated using crown rump length?

Answer 27

Crl (mm) + 42 = days gestation

4mm + 42 = 46 days