Ch 6 Abnormal Placenta + Cord Flashcards
Normal placental thickness?
2-4 cm
Placenta size is expressed how?
In terms of thickness
What conditions is placental thinning seen with?
-Hypertension
-Preeclampsia
-Placental infarctions
-IUGR
Do thick placentas (placentaomegaly) over 4cm typically have a normal outcome?
Yes
Placental thickening is m/c stimulated by what?
Myometrial contractions
(others are fibroids, abruption, etc)
Can the placental have different shapes?
Yes, can be bilobed or have accessory lobes
The selective loss of parts of the placenta + growth of other parts is referred to as what?
Trophoblastic trophotropism
(helps explain placental conditions like velamentous insertion + placental migration)
Where does placenta grow + where would it atrophy?
Grows: where there is sufficient decidua + vascular supply
Atrophies: due to not enough vascularity
What is a succenturiate lobe?
1 or more small accessory lobes that develop in the membranes at a distance from the periphery of the main placenta
What are succenturiate accessory lobes associated with?
Postpartum hemorrhage + infection
What is an annular placenta?
-Ring shaped placenta
-Attaches circumferentially into myometrium
What is associated with an annular placenta?
Prenatal + postpartum hemorrhage, due to poor separation
What is a circummarginate placenta?
When fetal membrane insertion is flat, is m/c
(20% of placentas)
What is a circumvallate placenta?
Thick, rolled chorioamniotic membranes peripherally
(1-7%)
Do circummarginate + partial circumvallate placentas have clinical significance?
No
What are complete circumvallate placentas associated with?
-Bleeding
-Abruption
-Preterm labor
-IUGR
-Perinatal death
-Fetal anomalies
Difference b/w circummarginate + circumvallate?
Marginate: smooth transition from membrane to villous chorion but there is increased distance from placental edge
Vallate: is similar, but there is a thick rolled edge at the transition
Classic SF of circumvallate placentas?
-Rolled up placental edge
-Can look like uterine synechiae b/c some views it appears as a linear structure protruding into fluid filled amniotic cavity
Can we see the “placental shelf” in circumvallate placentas?
Only early on in 2nd trimester, rarely seen by late 2nd trimester
(it is a transient + benign finding)
How common is placenta previa?
1 in 200 births
What is placenta previa?
When placenta implants in lower part of uterus + covers internal cervical os
Difference b/w placenta previa + low lying placenta?
Previa: inferior margin covers internal os
Low lying: inferior margin is within 2 cm of internal os
Should we do an EV if we see previa or low lying placenta?
Yes!
What other imaging modality can be used to evaluate placental invasion?
MRI
Risk factors for placenta previa?
-Advanced maternal age
-Previous C section/uterine scar
-Multiple gestations
-Previous elective abortions
-Smoking
-Cocaine
-Multiparity
How should we assess for placenta previa?
-Use CD over internal cervical os to look for vessels
-Measure from inferior tip placenta to internal os
-Ensure bladder isn’t too full
-Use EV or translabial to assess internal os
If a placenta is close to internal os in 1st trimester, will it ever move?
May migrate away from cx as pregnancy progresses
What does a morbidly adherent placenta mean?
-Abnormal implantation of placenta into uterine wall, describes accreta, increta + percreta
-Defect in decidua basalis which allows chorionic villi to invade into myometrium (sometimes extends into tissues as well)
What is placenta accreta?
When chorionic villi are abnormally adherent to uterine myometrium, instead of decidua
(m/c - 75%)
What is placenta increta?
When the villi infiltrate into the myometrial surface
(18%)
What is placenta percreta?
When the villi invade through myometrium into other maternal structures
(l/c - 7%)
Why has placenta accreta risen 10x in the US over the last 50 years?
Due to increased + repeat C sections
What is the m/c reason for an emergency postpartum hysterectomy?
A morbidly adherent placenta
Delivery is planned during what week range when a women has a morbidly adherent placenta?
Week 34-35
What are the 2 most important known RFs for placenta accreta?
-Placenta previa
-Previous C section
What is associated with placenta accreta?
So much
1st trimester SF suspicious for placenta accreta?
-Implantation of gest sac in lower uterus
-Multiple irregular vascular spaces in placental bed
-C section scar implantation
What is lacunae?
Small cavity/depression
In 2nd trimester, multiple vascular lacunae within placenta has a high or low chance for placenta accreta?
High sensitivity, low false-positive rate
(increased chance for placenta previa as well)
There is a loss of the normal hypoechoic retroplacental zone (clear space b/w placenta + uterus) with what condition?
Placenta accreta b/c placenta is growing into the uterine wall + removing that space
What is the most important SFs associated with placenta accreta in 3rd trimester?
Multiple vascular lacunae being present
Do placental venous lakes have an adverse pregnancy outcome?
No
What are placental venous lakes?
Irregular anechoic structures within placental tissue found under chorionic plate
Do venous lakes occur as gestational age increases or decreases?
Increases
Why does placental infarction occur with venous lakes?
Due to obstruction of spiral arteries found at periphery of placenta
What are placental infarctions associated with?
Retroplacental hemorrhage in up to 25% of term placentas
Why do subamniotic cysts occur?
From rupture of chorionic (fetal) vessels close to umbilical cord insertion into placenta
(associated with IUGR in 10% cases)
SF of subamniotic cysts?
-Multiple
-Protruding into amniotic cavity
-Anechoic
List the 2 primary nontrophoblastic tumors of the placenta?
-Chorioangiomas
-Teratomas
What is a chorioangioma?
-Benign vascular malformation of placenta
-Arises from primitive chorionic mesenchyme
Are chorioangiomas symptomatic?
-Small solitary ones are asymptomatic + little significance
-Multiple large ones (over 5cm) are symptomatic + associated with maternal/fetal complications in 30-50% of cases
What do chorioangiomas contain that can lead to severe fetal complications?
Arteriovenous shunts
What is placental abruption?
Premature separation of all/part of placenta from myometrium
(1% of pregnancies have this)
Placental abruption is classified according to the location of what?
Separation
(marginal, partial or complete)
How may the pt present with placental abruption?
-Acute abdominal + pelvic pain
-Vaginal bleeding
-Uterine tenderness
-Fetal distress
The resulting hemorrhage with placental abruption may occur as what types of blood clots?
-Retroplacental
-Intraplacental
-Marginal
-Subchorionic
(clots form to stop bleeding)
RFs of placental abruption?
-Hypertension
-Cocaine
-Smoking
-Trauma
-Uterine anomalies
-PROM
What is the amniotic band syndrome?
Sporadic condition due to rupture of amnion (w/o rupture of chorion), leading to oligohydramnios + passage of fetus from amniotic to chorionic cavity
(appears as echogenic lines/circle/band)
Early rupture of the amniotic cavity can lead to what?
Severe malformations of cranium, CNS, face + viscera
If amniotic bands tear, what can this lead to?
-Congenital amputations (ex toe comes off)
-Constriction rings
-Bizarre nonanatomic facial clefts
What is PMD?
Placental mesenchymal dysplasia - it is a newly recognized, rare placental vascular anomaly characterized by mesenchymal stem villous hyperplasia
What can PMD be mistaken for?
Molar pregnancy b/c of “grapelike vesicles”
What is a SUA?
-Single umbilical artery
-One of the m/c congenital anomalies
Is left or right umbilical artery m/c absent with SUA?
Left
If a fetus has SUA, what else should we be looking for?
High rate for other anomalies
Which 2 chromosomal abnormalities have been reported with SUA?
Trisomy 13 + 18
What is PRUV?
-Persistent right umbilical vein
-Common vascular variant where right umbilical/portal vein remains open (rather than the left one)
Is it hard to diagnose PRUV?
No, is often overlooked though
SF of PRUV?
Umbilical vein curves toward the left-side of stomach rather than toward the liver
Where is the GB located in regards to the PV with PRUV?
Is medial to vein (rather than normal lateral position)
Is PRUV normally an isolated finding?
Yes tho can have an increased risk of other anomalies like cardiac malformations
What is body stalk anomaly?
Complete absence of umbilical cord
(fatal condition linked to cocaine abuse)
What is limb body wall complex?
Very short umbilical cord
Length of a short cord?
Less than 35cm (associated with anomalies + is lethal/deathly)
The length of cord is an index of fetal what?
Activity - depends on tension created by fetus in 1st/2nd trimester
Difference of vasa + placenta previa?
Placenta: covers cervix
Vasa: blood vessels from cord cover cervix
What is suggested for moms to do for a good outcome if they have vasa previa, as it gets closer to end of pregnancy?
To do close follow up with possible hospitalization from 32 weeks onward
Best way to screen for vasa previa?
EV in late 1st or early 2nd trimester
Is the morbidity + mortality rate high with vasa previa?
Yes! 50-60% in intact membranes, 70-100% with ruptured membranes
The presence of umbilical cord cysts seen b/w 7-13 weeks have been reported at 3%, 20% of cases are associated with what?
Chromosomal/structural defects
The fetus is more likely to be abnormal if a umbilical cord cyst is located where?
-Near placental/fetal extremity of cord
-Or if cyst persists beyond 12 weeks gest
What are true umbilical cord cysts derived from?
-Embryonic remnants of allantosis + omphalomesenteric duct
-Located near cord insertion into fetal abdomen
(no risk of chromosomal anomalies)
What is edematous whartons jelly?
Complex umbilical cord mass containing cystic + solid components + internal calcifications
(suggestive of teratoma)
Is distinction b/w a hemangioma with degeneration of Wharton jelly + a teratoma hard to tell apart?
Yes
Normally, the herniation of midgut resolves by what week?
Week 14 - though it can persist into 2nd trimester + is consistent with an umbilical hernia
What is an umbilical hernia associated with?
Chromosome abnormalities
Difference in umbilical hernia, gastroschisis + omphalocele?
Hernia: completely covered by skin
Gastroschisis: no skin/membrane
Omphalocele: thin translucent membrane
2 m/c reasons why cord hematomas form?
Due to amniocentesis or cordocentesis
Hematomas of umbilical cord are rare, do they have high mortality rate?
Yes!
How to differentiate b/w cord hematoma from solid vascular lesions like teratomas + hemangiomas?
CD
Is umbilical cord artery /vein thrombosis with occlusion rare + associate with high perinatal mortality?
Yes
Thrombosis can form secondary to cord impairments like?
-Torsion
-Knotting
-Compression
-Hypercoiling
-Hematoma
Mechanical cord compression/accident can be caused by what?
-Nuchal/body cords
-Cord prolapse
-Cord entanglements
Abnormal cord position can occur from what?
-True knots
-Hypercoiling/twisting
-Long cords
-Abnormal insertions
-Strictures
What is a nuchal cord?
When the umbilical cord loops around the fetuses neck once or more times
(present in 24% of deliveries)
Is nuchal cord very serious?
Not if cord is only wrapped around once, if 3-4 times than yes but it is often resolved as the baby moves around
(is rarely associated with complications)
What is cord prolapse?
When cord slips down through cervix in front of baby at time of labor + delivery
How can we assess for cord prolapse?
CD - see flow of cord within the dilated endocervical canal + vagina
(very important we detect this)
Do true or false knots have significance?
True
What is a true knot?
When fetus actually passes through a loop or loops of cord
(fetuses 4x at risk for stillbirth)
What is the risk of a true knot?
Risk of tightening during labor
What is the purpose of cord coiling?
Makes cord flexible + strong, provides resistance to external forces that could compromise blood flow
(5% of fetuses have absence of coiling)
What are hypercoiled + hypocoiled cords associated with?
Hyper: aneuploidy, demise, etc
Hypo: vascular thrombosis of chorionic plate, etc
Entanglement of cords is risk in what type of twins?
MA twins (70%)
What is cord stricture?
Localized narrowing of cord with disappearance of Wharton jelly
What type of cord would experience cord stricture?
Long, hypercoiled cords + highly active fetuses
When do we use CD on umbilical artery?
ONLY when clinically indicated, do not do it always as it is not required in the protocol
Should we use CD on the umbilical artery with low risk pregnancies?
No, not of any value to this group of women. Only do it when mom has certain risk factors present.
Do we want high or low flow in diastole with cord doppler?
High
(with MCA doppler we want low diastole flow)
