Chapter 49 Flashcards by Allie Mitchell

Gestational Age

Menstrual age
First day of last menstrual period
12 days more than conceptual age

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Conceptional Age

Date of conception
Embryological age
Zygote-12 days after conception

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Ovulation

14 days after LMP
Ovum swept into Fallopian tube
Follicle becomes corpus lute and release estrogen and progesterone

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Fertilization

1-2 days after ovum is released

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Morula

rapid division

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Blastocyst

4-5 days after fertilization within the uterus

Trophoblastic cells that release hCG

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Implantation

12 days after fertilization
Zygote buried itself into one side of the uterus
Can cause bleeding

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Trophoblastic cells

Produce hCG
Causes decidual reaction
Nourishes early pregnancy
Eat into the decidua to form lacunae, which promote reproduction of the trophoblastic cells and form a capillary network that will begin the transfusion of blood from mother to embryo

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Double decidual sac sign

Interface between decidua capsularis and decidua along the far side of the endometrium
Reliable sign of early intrauterine pregnancy

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What form around the gestational sac in early pregnancy

Villi

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Up to 10 weeks

embryo

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after 10 weeks

fetus

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week 11 and 12

being fetal period

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The primary yolk sac is pinched off by ____; ___and___ are then formed

embryonic coelm ; amniotic and chorionic sacs

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After the amniotic and chorionic sacs form what is formed

the secondary yolk sac; marker of early pregnancy

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What is the most accurate form of dating through 12 weeks

Crown rump length

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How early can the crown rump length be demonstrated

5.5 weeks with TV

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IUP visible when hCG level is greater than

3000mIU/ml

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hCG level plateaus at how many weeks

10 weeks and decreases

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hCG level doubles every how many days

every 3.5 days up to 7 weeks

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What can we tell from hCG?

Does it correlate with size of sac?
Is it increasing the way it should?
Ectopic often does not increase properly
Trisomy 21 often increases more than it should
Is it decreasing before or later than it should?
Demise will cause a sudden drop
Trisomy 21 decreases later than 10 weeks

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Goals for First Trimester Ultrasound

Uterus and adnexa to visualize gestational sac
Measure fetal pole / embryo/ and/or sac
Heart rate
Multiples and chorionicity
Uterus, adnexa and cul de sac
Nuchal translucency if indicated

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Gestasional sac grows how fast

1mm per day

10 weeks average 35-45mm MSD

Appropriate placement and shape for gestational sac

fundus of the uterus ; oval/round

Decidual wall thickness of gestational sac

3mm or more

Mean Sac Diameter

length + width + height /3

Decidua Basalis

on the myometrial side of decidual reaction

Decidua Capsularis

the villi covering the developing embryo

yolk sac is seen between weeks

5 - 5.5 weeks | GS MSD- 12mm/ and no greater than 20 mm

Yolk sac diameter up to

6mm

Embryo seen at GS MSD of

18mm

Function of the yolk sac

Nutrients to embryo Hematopoiesis Develops embryonic endoderm that forms the primitive gut At 8 weeks with expansion of amnion it disconnects from the stalk Usually not seen after 12 weeks

Heart motion

4 mm CRL 5- 5.5 weeks Adjacent to YS

At how many weeks can the amnion membrane be seen

5.5 weeks

The amnion membrane separates what

the amnion from the chorion

The amnion and chorion fuse at ____ weeks

14-15

T/F: In a normal pregnancy the chorion may have low level echoes

True (waste from early embryo)

What happens at 5 weeks?

bilaminar embryonic disk undergoes gastrulation and converts into trilaminar embryonic disk Oranogenesis begins

What happens at 6 weeks?

At 6 weeks the trilaminar embryonic disk begins to fold which creates a C shaped embryo

During embryonic folding, what develops?

dorsal aspect of yolk sac incorporated into embryo, developing foregut, midgut, hindgut, and forming entire gastrointestinal tract, liver, biliary tract, pancreas

While embryonic folding continues what forms?

embryonic head, caudal portions, and lateral folds form, resulting in constriction or narrowing between embryo and yolk sac, creating the yolk stalk.

What three structures create the umbilical cord?

1. Yolk stalk 2. Connecting stalk 3. Allantois

When does the spine start to develop?

week 6

when does the brain start to develop?

week 7

What three vesicles form at week 8?

Prosencephalon Mesencephalon Rhombencephalon

The Rhombencephalon divides further into what?

Metencephalon: Cephalic section Myelencephalon: Caudal section

The echogenic line seen in the crainium in 8.5-9 weeks is called what?

Midline falx

The lateral ventricles also seen at in week 8.5-9 is called what?

choroid plexus

The brain is almost complete at week ___

week 10

When do limb buds begin to develop?

week 6, seen on US week 7

Hands and feet are fully developed at week ___, along with calcification of bones

weel 10

First organ to be functional is the ___

heart

The heart is seen on ultrasound at week __

week 5 (CRL of 4mm)

The heart is in the adult structure in how many weeks?

8 weeks

Heart rate at 6 weeks: 9 week: Late first and second trimester:

90-115 bpm 140-160 bpm 140 bpm

Additional tests for chromosomal abnormalities

Amniocentesis: 16 weeks Chorionic Villus sampling: 11-14 weeks Fetal death rate; 1:300