ERU 23- The First Trimester Flashcards
Zygote > Morula > blastocyst
Blastocyst:
Outer trophoblastic cells (produce hcg) > placenta and chorion
Inner part > embryo, amnion, cord, yolk sacs
Chorionic sac/gestational sac: outer
Amniotic sac: inner membrane
Chorionic cavity/extraembryonic coelom: secondary yok sac between these membranes
At what hcg level should a gestational sac be visible on TVUS? (What is the discriminatory zone?)
1,000 - 2,000
During what week of pregnancy does the decidual reaction occur?
Weeks 3-4
At what gestational age does a gestational sac appear?
Weeks 4-5
chorionic cavity
The space between the gestational sac and the amniotic sac. The location of the secondary yolk sac
Chorion frondosum
The decidualized tissue at the implantationsite containing the chorionic villi. The fetal contribution to the placenta
Chorionic laeve
The portion of the chorion that does not contain chorionic villi
chorionic villi
Fingerlike extensionof the trophoblastic tissue that invades the decidualized endometrium
decidua vasalis
the endometrial tissue at the implantation site.
The maternal contrivution of the placenta
Decidua capsularis
The portion of the decidua opposite the uterine cavity, across from the decidua basalis
decidua parietalis (vera)
The decidualized tissue along the uterine cavity adjacent to the decidua basalis.
How is the mean sac diameter used to calculate early dating?
MSD + 30 + GA in days
At what gestational age does the yolk sac appear?
What does the yolk sac produce?
5.5 weeks
AFP: important for hematopoiesis
What connects the embryo to the yolk sac?
The vitelline duct, which contains one artery and one vein
What is contained in the chorionic cavity?
The amniotic cavity?
Yolk sac and fluid
Amniotic fluid and embryo
At what gestational age are limb buds seen?
7-8 weeks
What is the cystic structure that can be seen in the fetal head at 7-8 weeks?
Rhombencephalon/Hindbrain: eventual 4th ventricle
At what gestational age does physiologic bowel herniation occur?
8-12 weeks.
What maternal and fetal layers form the placenta?
Maternal decidua basalis and fetal chorion frondosum
When is Nuchal Translucency measured?
What is a normal result?
11 - 13+6 weeks (when CRL is 45-84mm)
3-3.5mm
What criteria would define nonviable pregnancy in the first trimester?
Intradecidual sign
The sonographic presence of a small gestational sac within the decidua at approximately 4 to 4 and 1/2 Weeks with a mean sac diameter of approximately 2.5 mm. The first sonographic sign of pregnancy.
Double bleb sign / double decidual sac sign
Early amniotic sac with yolk sac. Present by 5.5 to 6 weeks
A rare form of gestational trophoblastic disease in which molar tissue invades the myometrium or adjacent anatomic structures
Chorioadenoma destruens
What is the most common cause of a single umbilical artery?
Secondary atrophy of a previously normal vessel
How is gestational age calculated using crown rump length?
Crl (mm) + 42 = days gestation
4mm + 42 = 46 days
