First Trimester Development

Question 1

What day of the cycle is an ovum released?

Answer 1

~14

Question 2

Where does fertilization of the ovum occur? When?

Answer 2

In fallopian tube 1-2 days after ovulation

Question 3

What happens after zygote cellular division?

Answer 3

forms 16 cell morula

Question 4

What happens at day 20?

Answer 4

zygote proliferates into blastocyst

Question 5

What is a blastocyst?

Answer 5

Contains trophoblastic cells and inner cell mass, becomes embryo

Question 6

What do trophoblastic cells release?

Answer 6

hCG

Question 7

What is the effect of hCG?

Answer 7

stimulates pregnancy response, begins to convert endometrium to decidua

Question 8

What is decidualization?

Answer 8

endo is converted to decidua by hCG

Question 9

When does the blastocyst enter the uterus?

Answer 9

4-5 days after fertilization, begins implanting

Question 10

When is implantation complete? What occurs?

Answer 10

12 days after fertilization, blastocyst has attached to posterior wall of ut

Question 11

What are chorionic villi?

Answer 11

formed by trophoblastic cells, encircle blastocyst and provide nutrients for future embryo

Question 12

What forms the embryo and yolk sac?

Answer 12

Maturation of inner cell mass

Question 13

When do amniotic and chorionic cavities form?

Answer 13

simultaneously with inner cell mass

Question 14

What is decidua?

Answer 14

Glycogen mucosa that helps support early pregnancy

Question 15

What are the 3 layers of decidua?

Answer 15

Capsularis: chorionic villi surrounding blastocyst
Parietalis: hormonal influence on endo tissue
Basalis: where blastocyst attaches, becomes maternal portion of placenta

Question 16

What is the chorion cavity?

Answer 16

• Embryonic tissue lining exterior of sac, invades decidua
• Highly vascular, surrounds amnion and YS

Question 17

When do amnion and chorion fuse?

Answer 17

16 weeks

Question 18

What are the layers of chorion?

Answer 18

Frondosum: located at implantation site
Laeve: faces endo cavity, thin coverage

Question 19

What is the amnion cavity?

Answer 19

• inside the sac
• encloses embryo and amniotic fluid
• becomes umb cord covering
• nonvascular

Question 20

When does the GS form? What is the rate of growth?

Answer 20

Forms week 4/5 of menstrual cycle, seen TA week 5
Grows 1mm/day

Question 21

What is the sono app of GS?

Answer 21

• double sac sign
• round, oval
• smooth, anechoic

Question 22

How thick is the echogenic ring surrounding the GS?

Answer 22

3 mm or greater

Question 23

At what GS sizes are the YS and embryo visible?

Answer 23

GS >10 mm= YS vis
GS >18 mm= embryo vis

Question 24

How do you calculate mean sac diameter?

Answer 24

L+W+H/3

Question 25

When does the primary YS form?

Answer 25

forms and disappears at week 4 and secondary forms

Question 26

What happens to the YS at weeks 8 and 12?

Answer 26

YS attaches to embryo via yolk stalk Wk 8: detaches from yolk stalk Wk 12: YS reabsorbs

Question 27

What is the yolk sac responsible for?

Answer 27

Responsible for hematopoiesis, formation of primitive gut, provides nutrients for embryo

Question 28

What is the sono app of the YS?

Answer 28

- earliest intragestational sac anatomy vis - not vis after 12 wks - donut shaped structure w/ echogenic walls & sonolucent center

Question 29

Visualization of YS predicts a viable pregnancy what percentage of the time?

Answer 29

> 90% of cases

Question 30

How large is a normal YS? What is considered abnormal?

Answer 30

2-5 mm, >5.6 mm at 5-10 wks = abnormal, thin walls = abnormal

Question 31

What causes suspicion of threatened ab?

Answer 31

nonvis of YS at MSD of 8 mm

Question 32

What size is fetal pole seen at? What rate does it grow at?

Answer 32

CRL 1-2 mm, grows 2 mm/day 1st tri

Question 33

What is the sono app of embryo & fetal pole at different weeks of gestation?

Answer 33

4-5 wks: TV 6-7 wks: TA Wk 2-8: embryo Wk 8/10 on: fetus

Question 34

What indicates lagging growth?

Answer 34

>1 wk discrepancy b/w meas. & menstrual age sac sz = MSD-CRL Normal >/= 5 mm Abnormal

Question 35

What is organogenesis AKA?

Answer 35

embryonic phase

Question 36

What is organogenesis?

Answer 36

- embryo assumes c-shape - fetal anatomy fully developed by end of 1st tri - wk 4-10

Question 37

What is developed by wk 10 of organogenesis?

Answer 37

- neurocranial axis - CV system - GI system - urogenital system - primitive skeleton & muscles

Question 38

What is the first organ to function?

Answer 38

heart

Question 39

When is the heartbeat visualized TA and TV?

Answer 39

TA: 6-7 wks TV: 5-6 wks

Question 40

What is the FHR during embryonic phase, mid 1st tri, and 2nd/3rd tri?

Answer 40

embryonic: 90 bpm mid 1st: 180 bpm 2nd/3rd: 120-160

Question 41

What is considered fetal bradycardia?

Answer 41

< 90 bpm, associated with fetal demise

Question 42

When is skeletal development? At what points in gestation do certain skeletal structures develop?

Answer 42

3-4 weeks post conception Wk 6: spine, limb buds Wk 8: skeletal ossification Wk 9: cranial bones

Question 43

What causes skeletal anomalies?

Answer 43

environmental, drug and genetic factors

Question 44

What is nuchal translucency? What is it associated with?

Answer 44

Max thickness of subcutaneous lucency at posterior fetal neck Used to assess genetic risk, increased NT associated w/ trisomies & abnormalities

Question 45

What is the criteria to evaluate nuchal translucency?

Answer 45

- 11-14 wks - CRL: 45-84 mm - midsag - embryo away from amniotic membrane - no hyperextension/flexion

Question 46

What is a normal hCG level at ~10 wks or 45 mm MSD for a viable pregnancy?

Answer 46

3000mlU/ml or greater

Question 47

If hCG levels are over 3000 and an embryo is not visualized, what is probable?

Answer 47

Ectopic

Question 48

What is the normal rate of increase of hCG?

Answer 48

Doubles every 3.5 days or 66% in 48 hours in first 7 wks

Question 49

What happens to hCG levels at 9-10 wks?

Answer 49

Levels plateau and decline

Question 50

What is the differences in hCG levels for ectopic and abnormal pregnancies?

Answer 50

Ectopic: lower hCG than IUP, abnormal progression Abnormal: lower levels for gest age, drastic decline before spont. ab.

Question 51

What are first trimester complications?

Answer 51

- subchorionic hemorrhage - ectopic - heterotopic preg - anembryonic gest - abortions - embryonic oligohydramnios - gest trophoblastic neoplasia - hydatidiform mole - choriocarcinoma

Question 52

What are indications for 1st tri ultrasound?

Answer 52

- gest age - confirm IUP/suspected ectopic - vaginal bleeding - pelvic pain - diagnose mult preg - confirm cardiac activity - guidance for sampling/device removal - assess fetal anomalies - mat pelvic masses/abnormalities - screen for aneuploidy (NT meas.) - suspected hydatidiform mole

Question 53

What is protocol for 1st tri US?

Answer 53

- Eval ut, adns, CDS (fibroids, masses, FF) - Eval of ovs (CL, ectopic) - GS location, meas - Presence of YS/embryo - Cardiac activity (M mode, cine)