OB first trimester registry review

Question 1

First trimester embryology

Answer 1

Zygote –> morula –> blastocyst

Question 2

First trimester

Answer 2

Weeks 1-12

Question 3

Fertilization

Answer 3

Usually occurs in the ampulla, within 24 hrs of ovulation (~day 14 of 28 day cycle)

Question 4

Zygote

Answer 4

A fertilized egg, undergoes rapid cell division

Question 5

Morula

Answer 5

Cluster of cells formed 3-4 days after fertilization

Question 6

Blastocyst

Answer 6

First time cell differentiation occurs by day 5

Question 7

Trophoblast

Answer 7

Outer ring of trophoblastic cells that begin to produce hCG. Will eventually become the chorion and placenta

Question 8

Embryoblast

Answer 8

Inner cell mass that will develop into embryo, amnion, cord, yolk sac

Question 9

hCG released by trophoblast

Answer 9

Maintains corpus luteum therefore maintaining endo via progesterone

Question 10

Decidualized (decidual reaction)

Answer 10

Endometrium prepares for implantation

Question 11

Implantation

Answer 11

Occurs 7-9 days after fertilization

Question 12

Chorionic villi

Answer 12

Finger like projections of trophoblast that form links into decidualized endo

Question 13

Yolk sac

Answer 13

Primary sac regressed by day 28 from LMP, secondary sac replaces

Question 14

hCG levels post implantation

Answer 14

Double every 48 hours until week 9

Question 15

Endometrium @ 4 weeks gestation

Answer 15

Multilayered appearance due to increased progesterone (decidualized), possible tiny anechoic sac

Question 16

5 weeks gestation

Answer 16

-1,000-2,000 hCG level
-GS seen by transvaginal
-double decidual sign confirms 2 layers of decidua

Question 17

hCG level for transabdominal GS seen

Answer 17

3,500 mIU/mL

Question 18

2 layers of decidua

Answer 18

Capsularis and parietalis

Question 19

Mean sac diameter (MSD)

Answer 19

L + H + W/ 3
Grows 1mm per day

Question 20

Gestational sac first seen with MSD

Answer 20

10mm

Question 21

Extraembryonic coelem

Answer 21

Space of the chorionic cavity between the amnion and chorion where the gestational sac is found

Question 22

5.5 weeks gestation

Answer 22

Gestational sac and yolk sac appear and are the first definitive sign of an IUP

Question 23

Secondary yolk sac

Answer 23

-Responsible for producing AFP, angiogenesis, hematopoiesis
-Is round, anechoic with thin echogenic rim measuring <6mm
-Connects to embryo

Question 24

Vitelline duct

Answer 24

Duct that connects the yolk sac to the embryo, consists of 1 artery and 1 vein

Question 25

Angiogenesis

Answer 25

The process of new blood vessels forming from existing blood vessels

Question 26

Hematopoiesis

Answer 26

The production of blood cells and platelets

Question 27

Enlarged yolk sac

Answer 27

Indicates impending demise (double bleb)

Question 28

Double bleb sign

Answer 28

Large yolk sac next to amnion

Question 29

6 weeks gestation

Answer 29

Embryo now seen within amniotic cavity adjacent to yolk sac. Must be seen by MSD 25mm. Fetal pole grows 1mm per day after 6 weeks

Question 30

Crown rump length (CRL)

Answer 30

MOST reliable estimation of gestational age in first trimester

Question 31

Fetal cardiac of fetus

Answer 31

-Must be noted by 5mm CRL, possibly earlier -Approx 100bpm increasing to 140 later in 1st trimester

Question 32

7 weeks gestation

Answer 32

Formation of limb buds and fetal head appears larger than body

Question 33

8 weeks gestation

Answer 33

Cystic structure noted within head-rhombencephalon

Question 34

Rhombencephalon

Answer 34

Eventually 4th ventricle

Question 35

9-12 weeks gestation

Answer 35

Normal for physiological bowel herniation migration of midgut and bowel at base of umbilical cord--> should be completed by 12 weeks

Question 36

10 weeks

Answer 36

No longer an embryo--> FETUS

Question 37

11+ weeks gestation

Answer 37

Fetal limbs and facial profile/cranium clearly evaluated and normalized

Question 38

Lateral ventricles

Answer 38

Filled with echogenic choroid plexus on either side of falx cerebri

Question 39

Placenta and umbilical cord

Answer 39

Well defined, crescent shaped and slightly echogenic mass of the tissue. Formed by decidua basalis and chorion frondosum

Question 40

Decidua basalis

Answer 40

Maternal component of placenta and umbilical cord

Question 41

Chorion frondosum

Answer 41

Fetal component of placenta and umbilical cord

Question 42

Hormones produced by placenta and umbilical cord

Answer 42

Several hormones + pregnancy-associated plasma protein a (PAPP-A)

Question 43

First trimester screening

Answer 43

-11-13w6d -Primarily for Trisomy 21 and 18 -Evaluate NT measurement + hCG + PAPP-A

Question 44

Nuchal tranlucency

Answer 44

Fluid filled layer between the fetus and the skin layer, SHOULDN'T measure >3mm

Question 45

Enlarge NT associated with

Answer 45

Trisomy 18, trisomy 21, trisomy 13, turners, cardiac defects; require karyotyping

Question 47

Karyotyping

Answer 47

Genetic test that analyzes the number, shape, and size of chromosomes in a sample of cells

Question 48

Guideline for 1st trimester screening

Answer 48

-CRL between 45-84mm -Midsagittal view -Fetal head in neutral position -Magnified image, head occupies most of image

Question 49

Midsagittal view landmarks

Answer 49

Rectangle shaped palate and mandible, nasal bone, thalamus, and brain stem

Question 50

NT measurement

Answer 50

INNER TO INNER at widest section in the back of neck when fetus is in neutral position, include entire fluid section but not skin

Question 51

Chorionic cavity

Answer 51

Area between amnion and chorion, typically fuse during first trimester but fully fused by 16 weeks

Question 52

Abnormal NT

Answer 52

Pocket of fluid visibly enlarged