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Ob/Gyne > Module 5.1 : First Trimester Normal > Flashcards

Module 5.1 : First Trimester Normal Flashcards

1
Q

pregnancy dates

A
  • pregnancy dated by weeks from first day of last menstrual period (LMP) or (LMNP)
  • 40 weeks completed gestation (41)
  • 280 days
  • 3 trimesters
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2
Q

1st trimester dates

A

0 - 13 6/7 weeks

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3
Q

2nd trimester dates

A

14 - 27 6/7 weeks

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4
Q

3rd trimester dates

A

28 - 40 weeks

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5
Q

embryo

A
  • the conceptus is called an EMBRYO from conception up to 10 week LMP
  • after 10 week called a FETUS
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6
Q

importance of ultrasound - first trimester

A
  • confirm pregnancy
  • confirm location ( intrauterine vs. extrauterine)
  • confirm size of embryo agrees with LMP dating (CRL)
  • confirm number of embryos
  • confirm viability ( fetal heart rate with m-mode)
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7
Q

ovulation

A
  • occurs at day 14 in ideal cycle
  • LH must surge for ovulation to occur
  • ovum ejected from follicle and propelled toward fallopian tube
  • lives fro 12 - 24 hours
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8
Q

sperm

A
  • 200 to 500 million sperm deposited near cervix on 300 to 500 reach ovum
  • 100 mill / ml is normal
  • under 20 million considered sterile
  • usually survive for 24 hours
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9
Q

fertilization

A
  1. sperm passes through the ZONA PELLUCIDA ( doesnt allow more sperm to fertilize ovum)
  2. sperm head enlarges to become male pronucleus and tail breaks off
  3. ovum completes second meiotic divison at this time to become female pronucleus
  4. both pronuclei fuse and the chromosomes intermingle
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10
Q

zygote

A

union of sperm and ovum

+ also called conceptus

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11
Q

morula

A
  • cluster of cells 12-16 BLASTOMERES

- morula remains the same size but the cells become smaller and smaller with each divisions

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12
Q

blastocyst

A
  • secretions cross the zone pellucida enter the morula forming a fluid filled cavity
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13
Q

The Journey

A
  1. the ovum travels 24 - 36 hours to reach the ampullae portion of the fallopian tube where fertilization occurs
  2. the blastocyst enters the uterus 6-7 days after fertilization
  3. implantation is complete by 11-12 days post ovulation or 9-10 days post fertilization
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14
Q

cleavage

A
  • rapid cell division without a change in the size of the original zygote is CLEAVAGE
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15
Q

blastomeres

A
  • chromosomes of the zygote arrange in the preparation for the 1st cleavage division the two daughter cells are called BLASTOMERES
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16
Q

blastocyst

A
  • fluid enters the zygote and separates it into 2 parts
    + TROPHOBLAST
    = outer cell to be placenta and chorion
    + EMBRYOBLAST
    = inner cell mass ( forms embryo, you sac, amnion)
  • once the zone pellucida disappears the blastocyst implants in the uterus
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17
Q

implantation

A
  • blastocyst attaches to endometrial epithelium
  • trophoblast differentiates in to 2 layers
    + SYNCYTIOTROPHOBLAST
    + CYTOTROPHOBLAST
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18
Q

syncytiotrophoblast

A
  • PRODUCES HCG

- invasively erodes the endometrial stroma and blastocyst sinks into endometrium

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19
Q

lacunae

A
  • the spaces eroded in the endometrium by the syncytiotrophoblast
  • become intervillous spaces of the placenta
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20
Q

cytotrophoblast

A
  • produces finger like projections that extend into the forming lacunar network called PRIMARY CHORIONIC VILLI
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21
Q

primary chorionic villi

A
  • finger like projection of cytotrohphoblast
  • form
    + chorion frondosum
    = villi directly at implantation site
    = early placenta
    + smooth chorion or chorion laeve
    = all the remaining villi around gestational sac (become chorionic membrane)
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22
Q

decidua (endometrium) reaction in the uterus

A
  • decidua cells of the endometrium increase in size and content for implantation due to progesterone
  • the endometrium will undergo a decidua reaction with an ectopic pregnancy as well regulating in pseudo sac
  • if pregnancy occur in bicornuate uterus the decidua reaction will occur in the non pregnant horn making it look like twins
  • trophoblastic cells of embryo produce hCG regardless of location of implantation supporting the corpus luteum on ovary
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23
Q

decidua layers of uterus

A

BCP

  • decidua BASALIS
  • decidua CAPSULARIS
  • decidua PARIETALIS ( VERA)
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24
Q

decidua basalis

A
  • part of decidua underlying the conceptus

- eventually becoming the maternal side of the placenta

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25
Q

decidua capsularis

A
  • part that covers over the gestational sac
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26
Q

decidua parietalis ( vera)

A
  • all remaining decidua
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27
Q

double decidual sign

A
  • sonographic descriptor
  • opposed layers of decidua parietalis and capsularis can be identified on early ultrasound
  • should always try to identify this to rule out pseudo gestational sac before embryo can be seen
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28
Q

gift wrap

A
  • in real pregnancy with gestational sac the layers of decidua will be easily indented and uniform in concentric layers
  • in pseudo sac the layers are not uniform and har to see
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29
Q

fusion of decidua

A
  • the decidua vera and capsularis fuse

- prior to this fusion there is potential space between the 2 layers this might cause some light bleeding

30
Q

amniotic cavity

A
  • small spaces occur between the inner cell mass and the trophoblast
  • by day 9 from conception these form the amniotic cavity
  • THE BLASTOCYST CAVITY NOW CALLED THE PRIMITIVE YOLK SAC ( not seen on ultrasound)
31
Q

double bleb sign

A
  • 2 blebs represent the early amnion and the yolk sac

- only seven on EV at 5 1/2 weeks

32
Q

embryo divison

A
  • while implantation is occurring the inner cell mass also changing
  • inner cell mass becomes the BILAMINAR DISC (embryonic disc) at 4 weeks LMP
33
Q

bilaminar/embryonic disc

A

2 layers

  • epiblast
  • hypoblast
34
Q

epiblast

A
  • gives rise to nearly all the cells of the embryo

+ also forms amniotic membrane which houses the amniotic fluid

35
Q

hypoblast

A
  • contributes to the formation of primitive ectoderm
36
Q

trilaminar disc

A
  • at 5 weeks
  • gastrulation occurs = formation of three layers
    + endoderm
    + ectoderm
    + mesoderm
37
Q

endoderm

A
  • first layer to differentiate (inner)

- linings of the GI and respiratory tracts

38
Q

ectoderm

A
  • 2nd layer to differentiate (outer)
  • forms CNS
  • surface ectoderm such as hair, skin and teeth, nails
39
Q

mesoderm

A
  • 3rd layer to differentiate (middle)

- generally forms muscle and bone

40
Q

embryonic stages

A
  1. zygote = fertilized ovum
  2. morula = same size but cell splitting
  3. blastocyst = when fluid enters the zygote at morula stage
  4. embryo = inner cell mass differentiates
  5. fetus = after 10 weeks LMP when embryogenesis is complete
41
Q

neurulation

A
  • begins at 3 weeks conception or 5 weeks LMP
  • formation of neural plate, neural folds, and neural tubes
  • neural tube closes around day 40 LMP
    + starts to close in middle thats progresses to the caudal and cephalic ends
42
Q

neural tube abnormalities

A
  • if caudal end doesnt close = spina bifida

- if cephalic end doesnt close = acephaly

43
Q

visualizing embryo on ultrasound

A
  • the decidua basalis and chorion frondosum appear as thickened area along gestational sac
  • embryonic pole develops in close proximity to chorion frondosum
44
Q

yolk sac formation

A
  • head and tail of embryo fold in, incorporating part of the primitive yolk sac
  • the remaining yolk sac called SECONDARY YOLK SAC
    + seen on ultrasound from 5 to 10-12 weeks LMP
45
Q

yolk sac function

A
  • provides nutrients prior to circulation
  • hematopoiesis starts in yolk sac
  • forms vessels
  • formation of digestive tract
  • development of sex glands
46
Q

allantois

A
  • diverticulum ( pouch) of the yolk sac

- forms umbilical vessels and also involved in formation of the urinary bladder

47
Q

growth - gestational sac

A
  • grows 1.1mm/day
48
Q

growth - embryo

A

1-2mm/day up to 8 weeks

49
Q

growth - yolk sac

A
  • 6mm is upper limit of normal before 10 weeks
50
Q

measurements

A

TAKEN INNER TO INNER

51
Q

gestational sac sizes

A

Mean Gestational Age Mean Sac Diameter
6 weeks 0 days 1.5cm = L+W+H/3
7 weeks 0 days 2cm
8 weeks 0 days 3cm

52
Q

EV scan at 4 weeks

A

gest sac 2-3mm

53
Q

EV scan at 5 weeks

A

gest sac 5-6mm

yolk sac 2-3mm

54
Q

EV scan at 6 weeks

A

CRL = 3-4mm

FH seen

55
Q

EV scan at 7 weeks

A

CRL= 12-14mm

56
Q

pregnancy tests

A

2 types

  • qualitative
  • quantitative
57
Q

qualitative pregnancy test

A
  • by urine
  • takes short time
  • can detect at even earlier than 4 weeks LMP
  • must meet certain threshold to be positive
  • negative does not exclude pregnancy
  • not numbers
58
Q

quantitative pregnancy test

A
  • by blood
  • tests beta sub unit of human chorionic gonadotropin (b hCG)
  • takes 8 hours and very sensitive
  • having negative test by this method excludes pregnancy
  • will show positive 23 days from LMP
  • b hCG plateau at 8 weeks
59
Q

mean sad diameter in relation to beta hCG

A
  • 30mm MSD equal 8 weeks
60
Q

units for beta hCG

A
  • 1st international reference preparation (FIRP)
  • 2nd international standard (SIS) - values 1/2 of FIRP
    + OLDEST
  • 3rd international standard (TIS) - values same as FIRP
61
Q

discriminatory zone

A
  • with a beta hCG test of 1000mIU/ ml SIS, you should see small gestational sac = 4 weeks LMP by EV
  • 1800 mIU/ml = 5 mm sac = 5 weeks trans abdominal
62
Q

ectopic pregnancy

A
  • should be considered if no IUP is visualized when the hCG is at or greater than the discriminatory zone
    + 500-1000mIU/ ml (SIS) = endovaginally
    + 1000-2000mIU/ml (FIRP) = endovaginally
  • mIU = milli international units
63
Q

fetal heart motion

A
  • should be detected if CRL of embryo is 5mm or greater by EV
64
Q

levels of beta hCG

A
  • should double every two days in normal intrauterine pregnancy until 8 weeks gestation
65
Q

example - if patient hCG is 1000 mIU / ml on Monday what would it be on Wednesday?

A

1000 x 2 = 2000 mIU / ml

66
Q

ectopic pregnancy effect on hCG levels

A
  • because decidua not great access to maternal circulation so hCG may be less than doubling or the saw
67
Q

high. beta hCG

A
  • indicates
    + twins ( multiples)
    + hydatitiform moles (more genetic material)
    + choriocarcinoma
    + teratomas (overgrown ecto,endo,meso tumor)
    + gonadotropin producing tumor
68
Q

low beta hCG

A
  • indicates
    + ectopic
    + missed abortion (fetal demise)
    + inaccurate dates
69
Q

pseudocyesis

A
  • condition where a women feels pregnant
    + nausea, full feeling in pelvis, bloating
  • pregnancy test is negative and uterus will be normal non gravid
  • no IUP detected within endometrium
  • can psychologically create these symptoms
70
Q

early OB protocol

A
  • sag midline uterus
  • trans vag, cx, funds
  • MSD if no embryo identified
    + mean sac diameter = L + W + H / 3
  • if embryo seen measure CRL 3 times
    + to be accurate
    + may be magnified
  • document yolk sac if seen
    + measure
  • m-mode heart rate if motion seen
  • document maternal ovaries
  • document menatoma near gestational sac if identified
  • document free fluid if seen ( 2 planes)
  • if 12-14 weeks size do CRL and BPD
  • endovaginal always if under 7 weeks gestation
  • endovaginal when necessary
    + no embryo
    + no embryonic heart beat seen

Ob/Gyne (24 decks)

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