OB test 2 ch. 47-51 Flashcards Preview

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Flashcards in OB test 2 ch. 47-51 Deck (74)
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cavity where the fetus exists

amniotic cavity



-secreted by trophoblastic cells

-indicates pregnancy

-FIRST TRIMESTER: hCG levels should double every few days (or every 48 hrs) then will likely decrease after the first trimester.

-blood hCG should be positive 7-10 days conception age


primary yolk sac vs secondary yolk sac

-at 23 days menstrual age, the primary yolk sac is pinched off, forming the secondary yolk sac.

-we only see the secondary yolk sac under ultrasound

-Secondary yolk sac contains the amniotic and chorionic cavities


how do we (sonographers) date a pregnancy? what method do we use?

-sonographers use gestational age (also known as menstrual age) to date pregnancy.

-the first day of the last menstrual period (LMP) as the beginning of the gestation.


how do embryologists date a pregnancy?

-embryologists use conceptual age (also known as embryologic age) with conception being the first day of pregnancy.


decidua basalis

-the portion on the myometrial side or burrowing side.

-the part of the decidua that unites with the chorion to form the placenta


decidua capsularis

-the villi covering the developing embryo.

-the part of the decidua that surrounds the chorionic sac


double decidual sac sign

-reliable sign of an early pregnancy

- its the interface between the decidua capsularis and the endometrial cavity.


when do hCG levels begin to plateau?

9-10 weeks


if hCG levels are super high, its an indication of...

molar pregnancy OR multiple pregnancies


if hCG levels don't double like they should (in the first trimester) its an indication of...

ectopic pregnancy


when does the amnion and chorion fuse together?

at the end of the third month of gestation.

-chorioamniotic fusion occurs at approx. 14 to 15 weeks (chp 47 p.p)


when does a fetus' heart begin to beat? when can we see this under ultrasound?

-the heart begins to beat at 36 days -we can see heart tones under ultrasound at 46 days


how to calculate mean sac diameter (MSD) ?

its the average sum of the length, width, and height of the gestational sac.

length (mm) + width (mm) + height (mm) /3 = MSD


When should we expect to see the yolk sac & Embryo?

4-5 weeks; Embryo seen at 4 weeks as echogenic curved structure adjacent to yolk sac (chp 45 p.p.)

Yolk sac should be seen when MSD >12 mm 

Embryo should be seen when MSD >18 mm

*These measurements vary depending on which source is used*


When does bowel begin to herniate back into the fetus?

11 weeks; Bowel herniates out at 8-11 weeks, then returns to abdominal cavity (chp 45 p.p.)


What measurement should the yolk sac not exceed?

>6mm (chp 47 p.p.)


Cystic area in the head that is a normal structure, but can be confused with pathology?

Rhombencephalon (chp 47 p.p.)


What hormones do the corpus luteum secrete?



Decidua Parietalis

The altered endometrium lining the main cavity of the pregnant uterus other than at the site of attachment of the chorionic sac


Fertilization occurs within this region 1 to 2 days after ovulation

-fertilization most often occurs in the Ampulla portion of the fallopian tube A mature ovum is released and enters the distal fallopian tube via the fimbriae


Stages of fertilization

Fertilization occurs at distal end of fallopian tube, days 1-2. Fertilized conceptus is now referred to as a zygote which undergoes rapid cellular division to form the 16-cell morula, days 3-4. Further cell proliferation bring the morula to the blastocyst stage, days 4-5. Implantation happens within 12 days post fertilization into the uterine decidua Figure 47-1 p.1065

-12 days after conception (during implantation) conceptus is called zygote

- from time of implantation until end of 10th week menstrual age, conceptus is called embryo

-after 10 weeks, now called fetus



How many weeks should we be able to evaluate cranial anatomy?

28 weeks



absence of brain and cranial vault, most common cerebral abnormality


Pelvic mass in 1st tri

Corpus luteum cyst most common ovarian mass seen in 1st tri  

Fibroids are also common and increase in size in 1st tri due to estrogen stimulation

(Chapter 48)



Sub chorionic hemorrhage

most common cause of bleeding in the first trimester

Hemorrhage occurs between myometrium and margins of gestational sac due to process of implantation of fertilized ovum into endometrial cavity & myometrial wall. 


what is the most common location for an ectopic pregnancy?

Fallopian tube


What is the most life threatening location for an ectopic pregnancy?

Interstitial portion


Which ectopic pregnancy location causes loss of uterus?



How much gestational sac grows?

1mm per day in early pregnancy. Chapter 47