Chapter 49 Flashcards
Gestational Age
Menstrual age
First day of last menstrual period
12 days more than conceptual age
Conceptional Age
Date of conception
Embryological age
Zygote-12 days after conception
Ovulation
14 days after LMP
Ovum swept into Fallopian tube
Follicle becomes corpus lute and release estrogen and progesterone
Fertilization
1-2 days after ovum is released
Morula
rapid division
Blastocyst
4-5 days after fertilization within the uterus
Trophoblastic cells that release hCG
Implantation
12 days after fertilization
Zygote buried itself into one side of the uterus
Can cause bleeding
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
Double decidual sac sign
Interface between decidua capsularis and decidua along the far side of the endometrium
Reliable sign of early intrauterine pregnancy
What form around the gestational sac in early pregnancy
Villi
Up to 10 weeks
embryo
after 10 weeks
fetus
week 11 and 12
being fetal period
The primary yolk sac is pinched off by ____; ___and___ are then formed
embryonic coelm ; amniotic and chorionic sacs
After the amniotic and chorionic sacs form what is formed
the secondary yolk sac; marker of early pregnancy
What is the most accurate form of dating through 12 weeks
Crown rump length
How early can the crown rump length be demonstrated
5.5 weeks with TV
IUP visible when hCG level is greater than
3000mIU/ml
hCG level plateaus at how many weeks
10 weeks and decreases
hCG level doubles every how many days
every 3.5 days up to 7 weeks
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
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
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?
- Yolk stalk
- Connecting stalk
- 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