placenta/umbilical cord Flashcards
A discoid, highly vacular organ which weighs about 600g at delivery and is usually 2-4 cm thick.
Placenta
The maternal surface is highly irregular and divided into what?
cotyledons
THe fetal surface of the placenta is very smooth and covered by what? (2)
chorionic and amnionic membranes
What is the most important function of the placenta?
exchange of oxygen, waste products, and nutrients between mom and fetus
What does the placenta convert fetal steroids to ?
estrogen
Why does the placenta secrete progesterone?
to keep the myometrium quiet (secretes HCG in first trimester)
What is formed by proliferation of chorionic villi or chorionic frondosom from trophoblastic tissue and the maternal decidua basalis?
Placenta
Each functional unit of the placenta is known as what?
cotyledon
How many cotyledons per placenta?
12-20
Do we do placental grading anymore?
NO, used in 80’s and 90’s in hopes to associate it with the fetal well being
What are extra chorial types?
Placentas in which the membranous chorion does not extend to the edge of the placenta.
What are the two types of extra chorial?
Circumvallate placenta and circummarginate placenta
What is a small central chorionic ring which is surounded by thickened amnion and chorion called? ( this could predispose early separation from the uterine wall, creating antepartum bleeding and threatenig abortion. )
Circumvallate placenta
What is a central attachment of the membranes without a central ring?
Circummarginate placenta
What are the accessory types of the placenta?
Succenturiate, bipartite, annular
An accessory cotyledon with vascular connections to the main placenta???
Succenturiate
Why is succenturiate type of placenta dangerous?
Dangerous at delivery because the vessels between can rip, causing massive bleeding. Also, if the vessels cross anterior to the internal os of the cervix, things can get dicey at delivery.
What is it called when the placenta is divided into two lobes but united by primary vessels and membranes?
Bipartite
What is a ring-shaped placenta, wrapping around the entire uterus or at least a large circumference of it?
Annular
What is the typical thickness of the placenta?
less than 5cm (AP)
What are some causes for placental thickness?
Gestational diabetes Rh isoimmunization Maternal infection Multiple gestation Chorioangioma Maternal anemia Hydrops fetalis Sacrococcygeal teratoma Partial Molar preg. Placental abruption chromosomal abnormalities
A retro placental hematoma, which causes the mother terrible pain? Has a masslike appearance.
Placental abruption
Do we measure placental thickness?
NO
What are some causes for decreased placental thickness? less than 1.5 cm
Maternal preeclampsia
IUGR
Maternal diabetes, not gestational
intrauterine infection
When placental tissue implants near or even on top of the internal os of the cervix
Placenta previa
What causes placenta previa?
abnormally low implantation of the blastocyst
Placenta previa is more common in what situations?
multiparous women and patients with prior C-section or uterine surgery, and in women with intrauterine scarring (D&C’s)
What are the classic symptoms of placenta previa?
PAINLESS vaginal bleeding during the 3rd trimester
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The best diagnosis of placenta previa is in the 3rd trimester. WHY?
1st and 2nd trimester may have previa but with uterine growth the placenta moves up also called placental migration
Which is more likely to move up (migrate) an anterior placenta or posterior placenta?
anterior (anterior wall can expand more)
What can lead to a false positive diagnosis of previa? PITFALL
over distended maternal bladder, or have a focal myometrial contraction in lower uterine segment
When the placenta completely covers the internal cerival os. (symmetric, assymetric)
complete previa/total previa
Placenta partially covers the internal cervical os
Partial previa
The placenta encroaches on the internal os but does not cross it
marginal previa
When the placenta is in the lower uterine segment within 2cm of the internal os. This measurement is important. ****
Low-lying placenta
Premature separation of all or part of a normally implanted placeta from the myometrium.
abruption
What are symptoms of placenta abruption?
SEVERE abdominal PAIN with or without vag bleeding
Predisposing conditions to placental abruption
maternal hypertension advanced maternal age multi parity maternal vascular disease smoking trauma cocaine use uterine fibroids
Two types of abruption?
concealed, external abruption
Abruption that occurs in 20% of cases and hemorrhage is confined to the uterine cavity. The detachment can be complete and the consequences are severe because so much blood is lost between the mother and the fetus and pocketed between the placenta and uterine wall, instead of going to the baby.
Concealed
Abruption that occurs when blood drains through the cervical os and the patient presents clinically wth painful vaginal bleeding. Detachment is usually not as severe as concealed.
External abruption
Abnormal attachment of the placenta to the uterine wall.
Placental invasion
What is the most strong predisposing fctor in placental invasion?
prior uterine surgery (c-section)
low lying placenta or placenta previa that is anterior, and history of prior c-section are likely (60%chance) to result in what
placental invasion highly likely
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3 types of placental invasion
placenta accreta
placenta increta
placenta percreta
Chorionic villi are in direct contact with myometrium but do not invad it
placenta accreta
Chorionic villi invade the myometrium
placenta increta
Chorionic villi go through the myometrium to the serosa or outer covering of the uterus and often g into the bladder
placenta percreta
Large pools of maternal venous blood within the placenta. they are of no consequence clinically and appear as anechoic or hypoechoic round areas within the placenta which may exhibit slow venous flow under real-time conservation.
placental lakes
the pooling of maternal blood in the subchorionic space (superficially). of not clinical significance
fiber and deposition
caused by fetal bleeding into the intervillous space. no association with Rh incmpatibility ***
Of no significance
intervillos thrombosis***********
ischemic necrosis of placental villi from interference with maternal blood flow to the intervillous space
placental infarction (seen with hypertensive patients) (intervillous thrombosis is common with this) (anechoic or hyporechoic areas seen in placenta on ultrasound but no flow)
An accumulation of blood beeneath the chorion. Common finding in the 1st trimester. Radiologist wont mention it.
subchorionic/sub membranous hematoma
what is the most positive predictive value in predicting a good outcome for the fetus?
fetal heart beat
Vascular tumor of the placental tissue which occurs in 1 in 5000 pregnancies
chorioangioma
What are complications with chorioangioma when the tumors are large? >5cm
Polyhydramnios and fetal hydrops
associated with increased maternal serum alpha-fetoprotein
On ultrasound a solid well circumscribed placental mass, possibly near the cord insertion site.
chorioangioma
What does the umbilical cord contain?
2 umbilical arteries (deoxygenated blood away from the fetus) 1 Umbilical vein (oxygenated blood from mom to fetus)
What gives the candy cane appearance?
Umbilical arteris are longer than the vein and are twisted around the vein
what is the cord surrounded by?
protective Wharton’s jelly
WHat is the function of the umbilical cord
to allow the exchange of oxygenated blood and wastes between the mother and the fetus
How long is the cord at term?
50-60cm
What is the most commonly encountered cord abnormality in 1% of all pregnancies
two vessel cord (only one ear of mickey mouse) use color around bladder and will see only one artery
Is a two vessel cord concerning?
the fetus is not at risk due to 2 vessel cord but it could be associated with fetal abnormalities
What abnormalities may be associated with two vessel cord?
unilateral renal agenesis or other genitourinary tract anomalies trisomy 13,18,21 cardiovascular anomalies omphalocele central nervous system anomalies
Wharton’s jelly accumulation can appear as what?
umbilcal cord cyst
Umbilical cord cysts
developmental and usually asymptomatic/ originate as remnants of the omphalomesenteric duct when they are close to the fetus/ originate from allantoic duct when small and located away from the fetus
How do you differentiate an umbilical cord cyst from a umbilical vein Varix?
Varix will have flow but no flow in a cyst
Are nuchal cords important to image?
No, they are inconsequential. Occur in 2nd and 3rd trimester and you never documet them. Dr will check for the cord around the neck before delivery.
When the cor protrudes through the cervix or next to a presenting part in an open cervix.
Umbilical cord prolapse
Is umbilical cord prolapse important?
Yes absolutely an emergency. THe baby can asphyxiate by cuttingoff his own blood supply
“vessesls first” When cord crosses the cervical os, passing between the cerivx an the presenting part when membranes are intact. associated with velamentous insertion of the cord
vasa previa
What can occur secondary to knotting or torsion of the cord but is not commoly associated with that?
Umbilical vein thrombosis ( most likely, it may occur after percutaneous umbilical cord blood sampling procedure or intrauterine transfusion )
When is umbilical vein thrombosis more frequently seen?
in infants of diabetic mothers and in fetuses with nonimmune hydrops (outcome is almost always fetal death )
What is rare an associated with monochorionic, monoamniotic twins?
umbilical knots
When attachment of the cord is to the membranes rather than to the placental mass itself?
velamentous insertion
The cord travels for some length under the membranes before it attaches to the edge of the placenta
velamentous insertion ( can be associated with IUGR, preterm birth, and congenital anomalies )
Another name for marginal insertion? *****
Battledore insertion (KNOW)
When the attachment of the cord is at the edge of the placenta instead of centrally?
Marginal insertion ( battledore insertion )
