Placenta Flashcards
after implantation the trophoblast begins to differentiate into two cell layers:
the outer syncytiotrophoblast and the inner cytotrophoblast.
As the trophoblast invades the decidua, it breaks down decidual blood filled spaces known as
lacunae
network of lacunae evolves into
intervillous spaces of the placenta.
normal appearance of placenta (3)
Relatively homogeneous
Retroplacental clear space is hypoechoic
Venous laking
what are placental venous lakes
formation of hypoechoic cystic spaces centrally within the placenta
is there flow within the placental lakes
low-velocity intraplacental laminar flow
what are placental lakes associted with
increased placental thickness
placenta accreta spectrum and abnormal placental villous adherence
placental insufficiency, especially if seen early in pregnancy
normal placenta attaches to
the decidua basalis
In the 1st and 2nd trimester sonograms will show what placenta
a low lying placenta or placenta previa that will convert to a normal higher position when re-evaluated in the 3rd trimester
low lying placenta moving known as
“placental migration or retraction”
what is placenta migration due to
to differential growth rates between the uterus and placenta
< ______ cm abnormal at 20 weeks for placenta length
<14cm
< _______ cm abnormal at 23 weeks for placenta length
<15cm
> ______ cm abnormal at 20 weeks for placenta thickness
> 3 cm
> ______ cm abnormal at 23 weeks for placenta thickness
> 4cm
cord should be inserted where on the placenta
Middle
what are are succenturiate lobes
single or multiple lobes connected to the main body of placenta by velamentous connection of the umbilical vessel (vessels traversing the membrane).
what is the concern of not seeing the accessory lobe?
that the lobe may be retained after delivery
what is bilobed placenta
It is referred to two similarly sized placental lobes separated by intervening membrane. May still have vasculature across membrane
what is Velamentous cord insertion
abnormal condition during pregnancy
umbilical cord inserts into the fetal membranes (choriamniotic membranes), then travels within the membranes to the placenta (between the amnion and the chorion).
what is CIRCUMVALLATE PLACENTA
fetal membranes (chorion and amnion) "double back" on the fetal side around the edge of the placenta. chorionic plate is smaller then the basal plate (normal variant)
What is circumvallate placenta associated with
associated with increased chances of placental abruption and hemorrhage
usually no harm tho
free margin of the circumvallate placenta can mimic
a fetal membrane
Placenta membranacea aka
placenta diffusa
what is Placenta membranacea
all or most fetal membranes remain covered by chorionic villi, because the chorion has failed to differentiate into chorion leave and chorion frondosum.
sono appearance of Placenta membranacea
placenta that is covering most or the entire uterine wall
What is placenta previa
placenta that partially or completely covers the internal os.
marginal previa is
interal os is partially covered
low lying placenta is
placental the edge is within 2 cm but not covering any portion of the internal os
main risk factor of placenta previa
bleeding
when is placenta previa usually not asymptomatic
the time of labour and delivery
is it easier to see placenta previa/low lying placenta in 2nd/3rd trimester
no more difficult as time goes on, fetal parts get in the way of seeing it
Most significant factors contributing to the relatively high false positive diagnosis of Placenta Previa are (2)
Distortion of lower segment (by over distended bladder)
Focal myometrial contractions
first modality for imaging placenta previa
US
