Reproductive: Placenta and Cord Flashcards by John Mahon

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.

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What imaging features are common in normal placental aging?

Hypoechoic areas
Septations
Randomly distributed calcifications

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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.

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What are the most common types of abnormal placenta morphology?

Bilobed placenta
Succenturiate lobe
Circumvallate placenta

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What is this placenta morphology?

Bilobed placenta (two relatively equal sized lobes connected by a thin strip)

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What is this placenta morphology?

Placenta with a succenturiate lobe (one or more small accessory lobes)

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What is this placenta morphology?

Circumvallate placenta (rolled placental edges with a smaller chorionic plate)

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A bilobed placenta is associated with an increased risk of…

Type 2 vasa previa
Post partum hemorrhage
Velamentous insertion of the cord

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A succenturiate lobe is associated with an increased risk of…

Type 2 vasa previa
Post partum hemorrhage

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A circumvallate placenta is associated with an increased risk for…

Placental abruption
Intrauterine growth restriction

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What is the placenta morphology?

Bilobed placenta

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What is the placenta morphology?

Main placenta (*) with a succenturiate lobe (**)

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What is the placenta morphology?

Circumvallate placenta (rolled up edges)

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What is the normal thickness of the placenta?

1-4 cm

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Differential for a thin placenta (< 1 cm)

Placental insufficiency
Maternal hypertension
Maternal diabetes
Trisomy 13
Trisomy 18
Toxemia of pregnancy

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Differential for thick placenta (> 4 cm)

Fetal hydrops
Maternal diabetes
Severe maternal anemia
Congenital fetal cancer
Congenital infection
Placental abruption

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Placental abruption

Premature separation of the placenta from the myometrium

Note: This is painful. Technically a subchorionic hemorrhage is a marginal abruption.

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Risk factors for placental abruption

Cocaine use
Hypertension

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Which type of placental abruption has the worst prognosis?

Retroplacental abruption

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Placental abruption

Note: Anechoic/mixed echogenicity collection beneath the placenta causing disruption of the retroplacental complex.

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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)