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OB/Gyn > The normal first trimester > Flashcards

The normal first trimester Flashcards

0
Q

what is gestational age?

A

used by clinicians and sonographers

aka menstrual age

1st day of pregnancy is 1st day of LMP

adds 2 weeks (14 days) to conceptual age

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1
Q

What is conceptional age?

A

used by embryologists

aka embryologic age

1st day of pregnancy is conception

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2
Q

what is the ovum?

A

egg released from ruptured graffian follicle

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3
Q

what is the zygote?

A

fertilized ovum

for 12 days after conception during implantation process

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4
Q

what is the morula?

A

16 stage cell and greater

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5
Q

what is a blastocyst?

A

enters uterus at day 4-5 after fertilization

implants into the endometrial lining lining begins 7-9 days after fertilization

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6
Q

What is the baby call the Embryo?

A

from implantation until end of 10th week

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7
Q

When is ovulation

A

day 14 of 28 day cycle

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8
Q

fertilization occurs when?

A

within 1-2 days after ovulation

in distal Fallopian tube

fertilized ovum becomes ZYGOTE - zona pellucida forms around zygote prevents sperm from penetrating

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9
Q

What happens when the ruptured graffian follicle becomes corpus luteum

A

secretes progesterone and estrogen

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10
Q

What is the job of the morula?

A

continues cellular proliferation

becomes blastocyst - fluid filled cavity

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11
Q

What does the blastocyst consist of?

A

blastocyst

trophoblast

inner cell mass

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12
Q

What happens during the blastocyst stage?

A

Contains trophoblastic cells (cells that make up the placenta)

secretes hCG (causes endometrium to convert to decidua)

form chorion and placenta

“inner cell mass” become future embryo, yolk sac and amnion

enters uterus 4-5 days after fertilization

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13
Q

When is implantation completed?

A

6-9 days post fertilization (super complete by day 12)

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14
Q

What do trophoblast produce?

A

enzymes

create lacunae (blood pools formed by eroded maternal capillaries)
which nourish trophoblastic cells
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15
Q

What happens during implantation?

A

Enzymes produced by trophoblast

blood exchange network formed between mother and blastocyst

mature into placental/maternal circulation

when complete zygote buried in one wall of uterus

may cause light vaginal bleeding (implantation bleeding)

When complete trophoblast forms primary villi which encircle early gestational sac

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16
Q

What produces the hCG?

A

trophoblastic cells

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17
Q

What is the outer membrane of the gestational sac?

A

chorion

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18
Q

what is chorion frondosum?

A

early chorionic villi

attaches to endo becomes fetal side of placenta

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19
Q

is the chorion laeve involved with implantation?

A

no

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20
Q

what creates the “double bubble?”

A

the decidua capsularis + decidua vera parietalis = decidua vera (double bubble)

the white reaction around the gestational sac

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21
Q

What does the deciduas basalis turn into?

A

the placenta

maternal component of placental attachment

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22
Q

Do we ever see the primary yolk sac?

A

no we only see the secondary

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23
Q

When does the secondary yolk sac form?

A

approx day 23 (9 days after fertilization) primary yolk sac is “pinched off”

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24
Q

What happens with the secondary yolk sac during early gestation development?

A

seen sonographically in first trimester

Function: transfer of nutrients, hematopoiesis (forming blood cells), angiogenesis ( forming of blood vessels), formation of digestive tract

amniotic and chorionic cavities develop at the same time period

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25
Q

What happens around 5 weeks?

A

gastrulation - creating 3 germ cell layers

cardiovascular formation begins - begins to form immediately after gastrulation is complete in 5-8 weeks
(normal FHR 120-160bpm)

neurulation - formation of neural tube - complete closure by 7 weeks

26
Q

When is the embryonic phase?

A

week 6-10

27
Q

What happens in the embryonic phase?

A

organogenesis - main feature

all major internal and external structures begin to develop

embryo changes from flat dislike appearance to C-shaped structure, then human like appearance

CRL rapid development - 35mm by 10th week

most susceptible to teratogens

nearly all congenital malformation originate before or during

limb buds form

brain growth

midgut herniation

28
Q

When is the embryo most susceptible to teratogens?

A

during the embryonic phase

radiation, drugs, viruses, poor nutrition, toxins, alcohol, smoking etc

29
Q

When is the beginning of the fetal period?

A

weeks 11 and 12

30
Q

What happens in the fetal period?

A

organ and structures continue to grow and develop

fetal head disproportionately large almost 50% of the baby

fetal anatomy fully developed in late 1st trimester

31
Q

in maternal biochemistry what kind of relationship is there between quantitative bHCG and sonographic findings?

A

Direct relationship

32
Q

What is PAPP-A?

A

a pregnancy marker

associated plasma protein - A

insulin like growth factor in pregnancy

associated with growth processes bone and tissue formation

decreased levels in early pregnancy - marker for trisomy 21

levels may be linked with preterm labor and preeclampsia

33
Q

What is the TA sonographic technique and evaluation?

A

overall view of pelvic sturctures/anatomic relationships/pelvic masses

34
Q

What is the sonographic technique for TV?

A

more detailed evaluation of pelvic anatomy/pathology

sagittal and coronal/semicoronal planes

more detailed evaluations of gest. sac and contents, fetus

35
Q

Why would you use the transperineal sonographic techinque?

A

visualize cervix - sometimes done in first trimester…usually done in second

can be done if patient refuses tv

36
Q

Why would you use 3D evaluation in first trimester?

A

clinical value not really established

37
Q

Pulsed doppler should be used in first trimester?

A

only if absolutely necessary….use M-Mode.

38
Q

Who sets the standards for OB sonography?

A

ACR

AIUM

ACOG

39
Q

What major components are scanned in the first trimester?

A

Uterus and adnexa - presence of gestational sac

sonographic measurements of embryo and or gestational sac

presence/absence of fetal cardiac activity

fetal number and chronicity of multiple gestations

uterus, adnexa, cul-de-sac, ovaries

40
Q

What are the normal sonographic features of the gestational sac?

A

round or oval

fundal position

eccentrically placed

smooth contours

decidual wall thickness > 3mm

41
Q

if there is implantation in the LUS what are the placenta issues?

A

placenta accreta

placenta previa

42
Q

What is MSD?

A

mean sac diameter

43
Q

What is the measurement of the yolk sac between 5 - 5 1/2 weeks gestation?

A

> 12 mm MSD

embryo - > 18mm MSD

Gest Sac grows 1mm/day in early pregnancy

44
Q

Where do you find the yolk sac?

A

within the chorionic sac

45
Q

what is the earliest intragestational sac that you can see?

A

yolk sac - normally seen from 5 weeks gestation

46
Q

how is the yolk sac initially attached to the embryo?

A

yolk stalk

47
Q

What is the typical size of the yolk sac?

A

2-6 mm

over 6mm = abnormal

48
Q

When is the baby called a fetus?

A

after the first 10-12 weeks

49
Q

What is the zygote or conceptus?

A

undergoes rapid cellular division

forms 16-18 cell morula

50
Q

What is Decidua?

A

glycogen rich mucosa - nourishes early pregnancy

51
Q

What is the decidua capsularis?

A

layer of endo that heals over the implanted gestational sac

52
Q

What is decidua vera parientalis?

A

endo not in direct contact with gestational sac

53
Q

What is the lab values when the gestational sac is visualized transvaginally?

A

500-1000 mIU/ml

54
Q

What is the lab value for visualization of the gestational sac transabdominally?

A

1800 mIU/ml

55
Q

What should happen to the hCG levels every 48 hours in the first 6 weeks?

A

it should double

hCG levels plateau and then decline at 9-10 weeks

56
Q

What is suspected when hCG levels do not increase normally?

A

pregnancy is abnormal

possible ectopic or trisomy 21

57
Q

What two values are used in combination in 1st trimester (9-11 weeks) as a marker for trisomy 21 (downs syndrome)

A

hCG level and PAPP-A

58
Q

when can the amniotic cavity and membrane, chorionic cavity, yolk sac and embryo be seen?

A

5.5 - 6 weeks

59
Q

What happens to the yolk sac at approximately 8 weeks gestation?

A

with amniotic cavity expansion, the yolk sac, which lies between amniotic and chorionic membranes detaches from the yolk stalk

60
Q

When is the yolk sac resorb and no longer seen?

A

Sonographically by 12 weeks

persistent yolk sac does occur

persistent yolk sac my be visualized at placental umbilical cord insertion where amniotic and chorionic membranes fused

61
Q

At the beginning of the 5th week bilaminar embryonic disk undergoes gastrulation and converts into what?

A

trilaminar (three germ layer) embryonic disk

62
Q

What does visualization of the yolk sac predict?

A

viable pregnancy in 90% of cases

63
Q

When the yolk sac typically no longer seen?

A

by 12 weeks

OB/Gyn (14 decks)

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