Normal 1st Trimester Flashcards
What is gestational age?
Used by clinicians & sonographers
Also called MENSTRUAL age
1st day of pregnancy is 1st day of LMP
Adds 2 weeks (14 days) to conceptual age
What is conceptual age?
Used by embryologists
Also called EMBRYOLOGIC age
1st day of pregnancy is conception
What is ovum?
Egg released from ruptured Graffian follicle
What is zygote?
Fertilized ovum
For 12 days after conception during implantation process
What is morula?
16 stage cell and greater
What is blastocyt?
Enters uterus at day 4-5 after fertilization
Implants into the endometrial lining begins 7-9 days after fertilization
What is embryo?
From implantation until end of 10th week
What is fetus?
After first 10 weeks
What is ovulation?
Day 14 of 28 day cycle
When and where does fertilization occur?
Within 1-2 days after ovulation (12-24 hrs)
In distal fallopian tube (ampulla)
A fertilized ovum becomes a _________.
Zygote
What forms around the zygote to prevent sperm from penetrating?
Zona pellucida
A ruptured _________ becomes a corpus luteum. _________ & _________ is secreted.
Graffian follicle
Estrogen and progesterone
A zygote or conceptus undergoes _________ & forms 16-18 cell _________.
Rapid cellular division
Morula
As pregnancy progresses, the morula continues _________ and becomes a _________.
Cellular proliferation
Blastocyst
What is a blastocyst?
Fluid-filled cavity
What does a blastocyst consist of?
Blastocyst
Trophoblast
In cell mass
Trophoblastic cells make up the _________, secrete _________, and cause the endometrium to convert the a _________, which forms _________ and _________.
Placenta
HCG
Decidua
Chorion and placenta
What does an inner cell mass consist of?
Embryo
Yolk sac
Amnion
Implantation is completed within _________ days post fertilization.
6-9
An inner mass cell enters the uterus _________ days after fertilization.
4-5
Implantation is completed by day _________ posy fertilization.
12
Enzymes produced by _________ create lacunae.
Trophoblast
What is lacunae?
Blood pools formed by eroded maternal capillaries
Nourishes trophoblastic cells
When implantation occurs a _________ network is formed between the mother and blastocyst.
Blood exchange
The blood exchange network will mature into _________ circulation.
Placental/maternal
When circulation is complete, the zygote will…
Bury in one wall of the uterus - may cause light vaginal bleeding
When a complete trophoblast forms, _________ will encircle the early gestational sac.
Primary villi
Trophoblastic cells produce _________.
HCG
Chorion are _________ cells and are located in the _________ membrane of the gestational sac.
Trophoblastic
Outer
_________ Is early chorionic villi which attach to the _________ and becomes _________ of the placenta.
Chorion frondosum
Endometrium
Fetal side
_________ Is not involved with implantation.
Chorion laeve
_________ Is the maternal component of placental attachment - turns into placenta.
Decidua basalis
_________ Is the layer of endo that heals over the implanted GS.
Decidua capsularis
_________ Is when the endo is not in direct contact with the GS.
Decidua vera parietalis
_________ Is adjacent to decidua capsularis. Creates the “double bubble” sign.
Decidua vera
Inner cell mass develops into _________ and _________.
Embryonic disc
Primary yolk sac
Approx day _________, the primary yolk sac “pinches off” and forms _________.
23
Secondary yolk sac
When is the secondary yolk sac seen sonographically and what is its function?
1st trimester
Transfers nutrients, forms blood cells/vessels, formation of digestive tract
What 2 cavities develop at the same time?
Amniotic & chorionic
What is gastrulation?
Creating 3 germ cell layer of digestion tract
When does cardiovascular formation occur?
Begins immediately after gastrulation and is complete 5-8 weeks
When is a fetal HR initially seen and what is the BPM?
5 wks & alive
120-150
What is neurulation?
Formation of neural tube
Complete closure by week 7
What phase happens between weeks 6-10?
Embryonic phase
What happens during weeks 6-10?
Organogenesis - main features
All major internal & external structures begin to develop - malformations will be seen
Embryo changes from flat disc like appearance to c-shaped structure
Limb buds form, brain growth, midgut herniation
CRL rapid development - 35 mm by 10th week
During what weeks & phase are you most susceptible to teratogens?
Weeks 6-10
Embryonic phase
Weeks 11 & 12 are considered…
The end of the first trimester
What period begins during weeks 11 & 12?
Fetal period
What happens during weeks 11 & 12?
Organs and structures continue to grow
Fetal head is large
Fetal anatomy fully develops in late 1st trimester
Maternal biochemistry is a direct relationship between _________ and _________.
bHCG and sonographic findings
Gestational sac visualized through _________ at 500-1000 mUI/ml.
TV
Gestational sac visualized through _________ at 1800 mIU/ml.
TA
HCG levels should double every _________ hrs in the first _________ wks.
48
6
HCG levels plateau and then decline at _________ weeks.
9-10
_________ Levels in abnormal pregnancies usually do not increase normally. Give examples.
HCG
Ectopic, trisomy 21
What does PAPP-A stand for?
Pregnancy-associated plasma protein -A
What 2 levels are used in combination in 1st trimester as marker for trisomy 21 (Down’s Syndrome)?
HCG and PAPP-A
Why do TA’s during 1st trimester?
Overall view of pelvic structures/anatomic relationship/pelvic masses
Why do TV’s during the 1st trimester?
More detail of anatomy/pathology
More detail of GS, contents, fetus
Different planes
Why do transperineal during 1st trimester?
Visualize cervix
What 2 sonographic techniques can be used but aren’t all the time for 1st trimester scan?
3D and pulsed Doppler
1st trimester evaluation standards are outlined by?
ACR
AIUM
ACOG
Major components that should be seen when scanning a 1st trimester patient?
Uterus & adnexa - presence of GS
Measurements of embryo &/or GS
Fetal heart activity
Fetal #
Cul de sac & ovaries assessed
During the _________week of development a pregnancy can be identified.
5th
1-2 mm sac with echogenic ring - sonolucent center
Sonolucent center is in what cavity?
Chorionic
Describe the echogenic ring…
Trophoblastic tissue
Decidual reaction
What forms a double decidual sac sign?
Decidua capsularis and decidua parietalis
Describe the GS sonographically…
Round or oval
Fundal position
Eccentrically located
Smooth contours
Decidual wall thickness greater than 3 mm
What may be associated with the GS implanted in the LUS?
Placenta accreta or placenta previa
Yolk sac mean sac diameter is…
Greater than 12 mm at 5-5 1/2 weeks
Embryo mean sac diameter is…
Greater than 18 mm
GS grows _________ in early pregnancy.
1mm/day
What 4 structures are seen at weeks 5 1/2-6 wks?
Amniotic cavity & membrane
Chorionic cavity
Yolk sac
Embryo
When is a yolk sac usually seen?
From 5 weeks of gestation
Yolk sac is initially attached to embryo via _________.
Yolk stalk
When does amniotic expansion, the yolk sac, which lie between amniotic and chorionic membranes, detaches from yolk stalk?
Approx week 8
What is the size of the yolk sac?
2-6 mm
What does the yolk sac do and where is it located?
Nutrition to developing embryo
CHORIONIC CAVITY
Yolk sac predicts _________ 90% of the time.
Viability
Failure to see a _________, with minimum of 12 mm MSD, transvaginally is suspicious of abnormal pregnancy.
Yolk sac
Transabdominally, yolk sac should be seen with MSD of _________ but definitely seen at _________.
10-15 mm
20 mm
Yolk sac will reabsorb and disappear by week _________.
12
Why initially does there appear to be no space between the yolk sac and the embryo?
Amniotic cavity is small
_________ Cavity is initially the dumping ground for embryonic waste.
Chorionic
What takes over waste removal later in pregnancy and why?
Placenta
Amniotic cavity expands and chorionic cavity decreases
Fusion of membranes is called _________ and occurs at _________ weeks.
Chorioamniotic fusion
14-15
What 3 structures are brought together to form the umbilical cord?
Yolk stalk
Connecting stalk
Allantois
Spine forms at what week of gestation?
6th
Week 7 what structures are distinguishable?
Head and trunk
Spine
Limb buds
_________ Will appear as a cystic space in the POSTERIOR fetal brain during 8-11 weeks.
Rhombencephalon
Midgut herniation may be apparent and is normal till before _________ weeks.
12
What is apparent at week 9?
Limb movement
Midline flax, echogenic choroid plexus, lat vets
What is apparent during week 10?
Cerebellum, medulla, medulla oblongata in rhomboid fossa
Extremities and spine flex and extend
Palate fusion
Embryonic face with no detail - maxilla & mandible echogenic
Bowel, cecum, colon
After week 12, echogenic _________ is no longer visualized and echogenic _________ is seen within fetal ABD.
**DO NOT confuse with omphalcele or gastroschisis
Umbilical cord mass
Bowel
Week 11 is termed _________ period.
Fetal
What organ is the first to function?
The heart
When does the heart obtain its adult configuration?
End of 8th week of GS
CRL at 5 and alive should be _________ mm.
Greater than 4 mm
Rates of _________ BPM at 6 weeks increase to rates of _________ BPM at 9 weeks.
90-115
140-160
What approximate heart rate through remainder of late 1st and 2nd trimester?
140 BPM
How do you know the difference between a fetal heartbeat and the maternal heartbeat?
Fetal is over 100 BPM
What is the formula for MSD?
Length + width + height / 3
When is nuchal translucency preformed?
Weeks 11-14
What is the normal nuchal thickness?
Less than 3 mm
Twin gestations have _________ times greater mortality rate than singletons do.
7-10
Risk increases when twins are _________ and share _________ components.
Monozygotic
Membrane
Differences in nuchal translucency between normal twins may be an early sign of _________ syndrome.
Twin-to-twin transfusion
