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OB > First Trimester Development > Flashcards

First Trimester Development Flashcards

1
Q

What day of the cycle is an ovum released?

A

~14

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2
Q

Where does fertilization of the ovum occur? When?

A

In fallopian tube 1-2 days after ovulation

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3
Q

What happens after zygote cellular division?

A

forms 16 cell morula

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4
Q

What happens at day 20?

A

zygote proliferates into blastocyst

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5
Q

What is a blastocyst?

A

Contains trophoblastic cells and inner cell mass, becomes embryo

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6
Q

What do trophoblastic cells release?

A

hCG

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7
Q

What is the effect of hCG?

A

stimulates pregnancy response, begins to convert endometrium to decidua

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8
Q

What is decidualization?

A

endo is converted to decidua by hCG

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9
Q

When does the blastocyst enter the uterus?

A

4-5 days after fertilization, begins implanting

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10
Q

When is implantation complete? What occurs?

A

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

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11
Q

What are chorionic villi?

A

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

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12
Q

What forms the embryo and yolk sac?

A

Maturation of inner cell mass

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13
Q

When do amniotic and chorionic cavities form?

A

simultaneously with inner cell mass

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14
Q

What is decidua?

A

Glycogen mucosa that helps support early pregnancy

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15
Q

What are the 3 layers of decidua?

A

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

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16
Q

What is the chorion cavity?

A
  • Embryonic tissue lining exterior of sac, invades decidua
  • Highly vascular, surrounds amnion and YS
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17
Q

When do amnion and chorion fuse?

A

16 weeks

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18
Q

What are the layers of chorion?

A

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

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19
Q

What is the amnion cavity?

A
  • inside the sac
  • encloses embryo and amniotic fluid
  • becomes umb cord covering
  • nonvascular
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20
Q

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

A

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

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21
Q

What is the sono app of GS?

A
  • double sac sign
  • round, oval
  • smooth, anechoic
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22
Q

How thick is the echogenic ring surrounding the GS?

A

3 mm or greater

23
Q

At what GS sizes are the YS and embryo visible?

A

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

24
Q

How do you calculate mean sac diameter?

A

L+W+H/3

25
Q

When does the primary YS form?

A

forms and disappears at week 4 and secondary forms

26
Q

What happens to the YS at weeks 8 and 12?

A

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

27
Q

What is the yolk sac responsible for?

A

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

28
Q

What is the sono app of the YS?

A
  • earliest intragestational sac anatomy vis
  • not vis after 12 wks
  • donut shaped structure w/ echogenic walls & sonolucent center
29
Q

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

A

> 90% of cases

30
Q

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

A

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

31
Q

What causes suspicion of threatened ab?

A

nonvis of YS at MSD of 8 mm

32
Q

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

A

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

33
Q

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

A

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

34
Q

What indicates lagging growth?

A

> 1 wk discrepancy b/w meas. & menstrual age
sac sz = MSD-CRL
Normal >/= 5 mm
Abnormal </= 4 mm

35
Q

What is organogenesis AKA?

A

embryonic phase

36
Q

What is organogenesis?

A
  • embryo assumes c-shape
  • fetal anatomy fully developed by end of 1st tri
  • wk 4-10
37
Q

What is developed by wk 10 of organogenesis?

A
  • neurocranial axis
  • CV system
  • GI system
  • urogenital system
  • primitive skeleton & muscles
38
Q

What is the first organ to function?

A

heart

39
Q

When is the heartbeat visualized TA and TV?

A

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

40
Q

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

A

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

41
Q

What is considered fetal bradycardia?

A

< 90 bpm, associated with fetal demise

42
Q

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

A

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

43
Q

What causes skeletal anomalies?

A

environmental, drug and genetic factors

44
Q

What is nuchal translucency? What is it associated with?

A

Max thickness of subcutaneous lucency at posterior fetal neck

Used to assess genetic risk, increased NT associated w/ trisomies & abnormalities

45
Q

What is the criteria to evaluate nuchal translucency?

A
  • 11-14 wks
  • CRL: 45-84 mm
  • midsag
  • embryo away from amniotic membrane
  • no hyperextension/flexion
46
Q

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

A

3000mlU/ml or greater

47
Q

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

A

Ectopic

48
Q

What is the normal rate of increase of hCG?

A

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

49
Q

What happens to hCG levels at 9-10 wks?

A

Levels plateau and decline

50
Q

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

A

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

51
Q

What are first trimester complications?

A
  • subchorionic hemorrhage
  • ectopic
  • heterotopic preg
  • anembryonic gest
  • abortions
  • embryonic oligohydramnios
  • gest trophoblastic neoplasia
  • hydatidiform mole
  • choriocarcinoma
52
Q

What are indications for 1st tri ultrasound?

A
  • 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
53
Q

What is protocol for 1st tri US?

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

OB (6 decks)

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