Reproductive: Placenta and Cord Flashcards
When does the placenta first start being visible on ultrasound?
Gestational week 8 (as a focal thickening along the periphery of the gestational sac)
Note: It becomes disc-like around week 12.
What imaging features are common in normal placental aging?
- Hypoechoic areas
- Septations
- Randomly distributed calcifications
Ultrasound of placenta
Venous lakes (AKA placental lakes)
Note: These are a normal finding and they may or may not demonstrate flow on color Doppler.
What are the most common types of abnormal placenta morphology?
- Bilobed placenta
- Succenturiate lobe
- Circumvallate placenta
What is this placenta morphology?
Bilobed placenta (two relatively equal sized lobes connected by a thin strip)
What is this placenta morphology?
Placenta with a succenturiate lobe (one or more small accessory lobes)
What is this placenta morphology?
Circumvallate placenta (rolled placental edges with a smaller chorionic plate)
A bilobed placenta is associated with an increased risk of…
- Type 2 vasa previa
- Post partum hemorrhage
- Velamentous insertion of the cord
A succenturiate lobe is associated with an increased risk of…
- Type 2 vasa previa
- Post partum hemorrhage
A circumvallate placenta is associated with an increased risk for…
- Placental abruption
- Intrauterine growth restriction
What is the placenta morphology?
Bilobed placenta
What is the placenta morphology?
Main placenta (*) with a succenturiate lobe (**)
What is the placenta morphology?
Circumvallate placenta (rolled up edges)
What is the normal thickness of the placenta?
1-4 cm
Differential for a thin placenta (< 1 cm)
- Placental insufficiency
- Maternal hypertension
- Maternal diabetes
- Trisomy 13
- Trisomy 18
- Toxemia of pregnancy
Differential for thick placenta (> 4 cm)
- Fetal hydrops
- Maternal diabetes
- Severe maternal anemia
- Congenital fetal cancer
- Congenital infection
- Placental abruption
Placental abruption
Premature separation of the placenta from the myometrium
Note: This is painful. Technically a subchorionic hemorrhage is a marginal abruption.
Risk factors for placental abruption
- Cocaine use
- Hypertension
Which type of placental abruption has the worst prognosis?
Retroplacental abruption
Placental abruption
Note: Anechoic/mixed echogenicity collection beneath the placenta causing disruption of the retroplacental complex.
How can you differentiate a placental abruption from a myometrial contraction or fibroid?
A placental abruption will disrupt the retroplacental complex of blood vessels
Myometrial contractions/fibroids will displace the retroplacental complex (but not disrupt it)
Placenta previa
A low implantation of the placenta that covers part or all of the internal cervical os
Note: Classically associated with painless 3rd trimester bleeding.
What are the types of placenta previa?
At what point is a placenta considered “low-lying”?
When a placental margin is within 2 cm of the internal cervical os
How full should the bladder be when evaluating for placenta previa?
Empty (a full bladder can create a false positive appearance of placenta previa when there is none)
Painless vaginal bleeding in the 3rd trimester…
Think placenta previa
Disruption of the retroplacental complex vessels…
Think placental abruption
Placenta creta
Abnormal insertion of the placenta into the myometrium
What are the types of placenta creta?
- Accreta (mild)
- Increta
- Percreta (very bad)
Risk factors for placenta creta
- Prior c section
- Placenta previa
- Advanced maternal age
Fetal ultrasound
Placenta creta spectrum disease
Note: Placenta is nearly subjacent to the urinary bladder with thinning of the myometrium.
Placenta percreta
The most severe form of placenta creta where the placental villi penetrate through the myometrium (and can actually penetrate past the serosa and invade the bladder or bowel)
What is the most common benign tumor of the placenta?
Placenta chorioangioma (basically a hamartoma of the placenta)
Placenta chorioangioma
Note: Well-circumscribed hypoechoic mass in the placenta.
Diagnostic finding of placenta chorioangioma
Flow within the placental mass that pulsates at the fetal heart rate
Note: These are basically hamartomas that are perfused by fetal circulation.
Complications of placenta chorioangioma
If large enough (> 4 cm), they can sequester platelets and cause high output heart failure (fetal hydrops)
How can you differentiate a placental chorioangioma from a placental hematoma?
Chorioangioma will have pulsating Doppler flow (hematomas will not)
Which vessel is most often missing in a 2-vessel cord?
The left umbilical artery
Velamentous cord insertion
When the umbilical cord inserts into the fetal membranes >2 cm outside the placental margin (and then has to travel back through the membranes between the amnion and chorion to get to the placenta)
Velamentous cord insertion is associated with…
- Intrauterine growth restriction
- Growth discordance between twins
Velamentous cord insertion (cord inserts into the fetal membranes outside the placental margin)
Marginal cord insertion
When the umbilical cord inserts within 2 cm of the placental margin
Vasa previa
When the umbilical cord vessels cross (or almost cross) the internal cervical os
What are the types of vasa previa
Type 1: Fetal vessels connect to a velamentous cord insertion within the main placental body
Type 2: Fetal vessels connect to a bilobed placenta or succenturiate lobe
Nuchal cord
When the umbilical cord is wrapped around the fetal neck
Think omphalomesenteric duct umbilical cyst
Note: Cyst in the periphery of the umbilical cord.
What are the two major types of umbilical cord cyst?
- False cysts (more common)
- True cysts
What are the most common true umbilical cysts?
- Omphalomesenteric duct cyst (more peripheral)
- Allantoic cyst (more central)
Think allantoic umbilical cord cyst
Note: Cyst located centrally within the umbilical cord.
Umbilical cord cysts are associated with…
These are common (3%) and usually mean nothing, but if they persist into the 2nd/3rd trimester may be associated with trisomy 13 and trisomy 18 (look closely for other abnormalities)
