ANSWERS GRADED A+ 2025/2026
What are some common causes of *damage to the chorionic vessels* which causes
leakage of blood into the intervillous space (fetal-maternal hemorrhage)? - Damaged
chorionic vessels:
*abdominal trauma*
*'spontaneous' placental abruption* (or secondary to cocaine, HTN disorders, etc)
*Invasive procedures* (amniocentesis, CVS)
*Ruptured vasa previa*
What are four main ways that the *size or functional area* of the *placenta* can be
compromised? - 1. *ABRUPTION*: decreases the functional AREA of placenta
(spontaneous, trauma, procedures)
2. *MATERNAL DISEASE* (HTN)
-disease processes can cause smaller placenta
-smaller placenta decreases gas exchange results in FGR, asphyxia & malnourishment.
3. *INFECTION*
4. *CONGENITAL DEFECTS*
What is the *placental reserve*? - *OXYGEN in the placenta DURING a
CONTRACTION* when there is *NO other blood flow entering the placenta*
This is the O2 reserve that continues oxygenating the fetus until the contraction ends!!!
----Anything that reduced the size of the placent or the functioning of the placenta
decreases the reserve available to the fetus.
What are common risk factors for decreased placental perfusion/function? - >>
*EXCESSIVE UTERINE ACTIVITY*:
*Tachysystole, hypertonus* or leading to Placental abruption.
>> ABRUPTION
>> *Maternal HYPOTENSION*; when supine or with epidural
>> *Maternal HYPERTENSION*
>> *Placental changes*
--decreased durface area (abruption)
--edema (erythroblastosis fetalis)
--degenerative changes (HTN, diabetes, post due, IUGR)
--Calcifications (smoking, tobacco use)
,--Infarcts (post due)
--Infection (Chorio)
>> *Vasocontriction*
exogenous mostly sympathomimetics (EXCEPT EPHEDRINE)
Why do we give *EPHEDRINE* to expectant mothers who experience *Hypotension*
after placement of *Epidural? - HYPOTENSION can lead to decreased placental
perfusion (fetal asphyxia/acidosis)
*Ephedrine* will cause vasoconstriction to increase blood pressure without further
compromise the placental perfusion.
erythroblastosis fetalis is what?
What can this do to the placenta? - hemolytic disease in the newborn (HDN) caused by
a blood group (Rh factor) incompatibility between the mother and the fetus
-remember this can cause *EDEMA in the placenta* (thereby compromising plcental
perfusion/function)
*post-due dates*: will cause what kinds of changes to the placenta? - 'DEGENERATIVE
Lesions'
> *Calcifications*
> *Infarcts*
Additionally post-dates is associated with:
*Decreased Amniotic fluid* (Oligohydramnios)
By what mechanism of transport do gases transfer in the placenta?
What else uses this mechanism? - *SIMPLE DIFFUSION*:
--transport achieved by movement of O2/CO2 from areas of *high concentration to
areas of low concentration*
*NARCOTICS* also use this mechanism of transport.
How are *NARCOTICS* transported across the placenta? - *SIMPLE DIFFUSION*:
--transport achieved by movement of from areas of *high concentration to areas of low
concentration*
Just like O2/CO2 across the placenta.
How is *glucose* (carbohydrates) transported across the placenta? - *FACILITATED
Diffusion*
What uses *facilitated diffusion* to cross the placenta? - *GLUCOSE*
, Describe *umbilical circulation* (umbilical cord). - 3 VESSELS:
*One VEIN*: carries *oxygenated blood*!!! to the fetus from placenta (mother)
*Two ARTERIES*: carry *DE-oxygenated blood* from the fetus back to the placenta
What are the ways by which the *umbilical circulation* through the umbilical cord can be
interrupted? - --*Mechanical interruption*: i.e. BABY lays on cord, obstructs or grasps
cord
--*Vasospasm*
--*thrombosis*
--*"True knot"* in cord
--*Hypertrophy*?
--Hemorrhage
--Inflammation
What are cotyledons? -
How many cotyledons or lobules are on the placenta surface? - *15-20*
--A Cotyledon is perfused with MATERNAL blood from the spiral arteries (which grow
from myometrium into endometrium).
Each cotyledon/lobule consists of? - Branches from a *SINGLE, large mainstem Villus*
*Amniotic fluid* levels affect . . . . . - *CORD FUNCTION*
Fluid acts as a cushion & protects the vessels in the umbilical cord to allow FREE
FLOW of blood.
What is *Amniotic fluid* composed of? - clear
water, proteins, carbs, lipids, electrolytes, fetal cells, lanugo, vernix caseosa
*FETAL URINE & lung secretions*
When there is DECREASED placental perfusion & increasing hypoxia within the fetus
there will be SHUNTING of the fetal blood away from the fetal extremities & non-vital
organs . . . . . . . perfusion of blood will be prioritized to what organs? - *BRAIN*
*HEART*
*ADRENALS*
If fetus is hypoxic and shunting blood to the brain, heart and adrenal -- there will be
what? - *DECREASED RENAL perfusion* which will cause:
---> decreased urine production
---> decreased output
---> *Decreased Amniotic Fluid*
(Amniotic fluid is an indirect indicator of placental perfusion)
*Oligohydramnios* can be an indicator of what? - ---> *FETAL HYPOXEMIA*