Reproductive: Placenta and Cord

Question 1

When does the placenta first start being visible on ultrasound?

Answer 1

Gestational week 8 (as a focal thickening along the periphery of the gestational sac)

Note: It becomes disc-like around week 12.

Question 2

What imaging features are common in normal placental aging?

Answer 2

• Hypoechoic areas
• Septations
• Randomly distributed calcifications

Question 3

Ultrasound of placenta

Answer 3

Venous lakes (AKA placental lakes)

Note: These are a normal finding and they may or may not demonstrate flow on color Doppler.

Question 4

What are the most common types of abnormal placenta morphology?

Answer 4

• Bilobed placenta
• Succenturiate lobe
• Circumvallate placenta

Question 5

What is this placenta morphology?

Answer 5

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

Question 6

What is this placenta morphology?

Answer 6

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

Question 7

What is this placenta morphology?

Answer 7

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

Question 8

A bilobed placenta is associated with an increased risk of…

Answer 8

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

Question 9

A succenturiate lobe is associated with an increased risk of…

Answer 9

• Type 2 vasa previa
• Post partum hemorrhage

Question 10

A circumvallate placenta is associated with an increased risk for…

Answer 10

• Placental abruption
• Intrauterine growth restriction

Question 11

What is the placenta morphology?

Answer 11

Bilobed placenta

Question 12

What is the placenta morphology?

Answer 12

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

Question 13

What is the placenta morphology?

Answer 13

Circumvallate placenta (rolled up edges)

Question 14

What is the normal thickness of the placenta?

Answer 14

1-4 cm

Question 15

Differential for a thin placenta (< 1 cm)

Answer 15

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

Question 16

Differential for thick placenta (> 4 cm)

Answer 16

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

Question 17

Placental abruption

Answer 17

Premature separation of the placenta from the myometrium

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

Question 18

Risk factors for placental abruption

Answer 18

• Cocaine use
• Hypertension

Question 19

Which type of placental abruption has the worst prognosis?

Answer 19

Retroplacental abruption

Question 20

Answer 20

Placental abruption

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

Question 21

How can you differentiate a placental abruption from a myometrial contraction or fibroid?

Answer 21

A placental abruption will disrupt the retroplacental complex of blood vessels

Myometrial contractions/fibroids will displace the retroplacental complex (but not disrupt it)

Question 22

Placenta previa

Answer 22

A low implantation of the placenta that covers part or all of the internal cervical os

Note: Classically associated with painless 3rd trimester bleeding.

Question 23

What are the types of placenta previa?

Answer 23

Question 24

At what point is a placenta considered “low-lying”?

Answer 24

When a placental margin is within 2 cm of the internal cervical os

Question 25

How full should the bladder be when evaluating for placenta previa?

Answer 25

Empty (a full bladder can create a false positive appearance of placenta previa when there is none)

Question 26

Painless vaginal bleeding in the 3rd trimester…

Answer 26

Think placenta previa

Question 27

Disruption of the retroplacental complex vessels…

Answer 27

Think placental abruption

Question 28

Placenta creta

Answer 28

Abnormal insertion of the placenta into the myometrium

Question 29

What are the types of placenta creta?

Answer 29

• Accreta (mild)
• Increta
• Percreta (very bad)

Question 30

Risk factors for placenta creta

Answer 30

• Prior c section
• Placenta previa
• Advanced maternal age

Question 31

Fetal ultrasound

Answer 31

Placenta creta spectrum disease

Note: Placenta is nearly subjacent to the urinary bladder with thinning of the myometrium.

Question 32

Placenta percreta

Answer 32

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)

Question 33

What is the most common benign tumor of the placenta?

Answer 33

Placenta chorioangioma (basically a hamartoma of the placenta)

Question 34

Answer 34

Placenta chorioangioma

Note: Well-circumscribed hypoechoic mass in the placenta.

Question 35

Diagnostic finding of placenta chorioangioma

Answer 35

Flow within the placental mass that pulsates at the fetal heart rate

Note: These are basically hamartomas that are perfused by fetal circulation.

Question 36

Complications of placenta chorioangioma

Answer 36

If large enough (> 4 cm), they can sequester platelets and cause high output heart failure (fetal hydrops)

Question 37

How can you differentiate a placental chorioangioma from a placental hematoma?

Answer 37

Chorioangioma will have pulsating Doppler flow (hematomas will not)

Question 38

Which vessel is most often missing in a 2-vessel cord?

Answer 38

The left umbilical artery

Question 39

Velamentous cord insertion

Answer 39

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)

Question 40

Velamentous cord insertion is associated with…

Answer 40

• Intrauterine growth restriction
• Growth discordance between twins

Question 41

Answer 41

Velamentous cord insertion (cord inserts into the fetal membranes outside the placental margin)

Question 42

Marginal cord insertion

Answer 42

When the umbilical cord inserts within 2 cm of the placental margin

Question 43

Vasa previa

Answer 43

When the umbilical cord vessels cross (or almost cross) the internal cervical os

Question 44

What are the types of vasa previa

Answer 44

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

Question 45

Nuchal cord

Answer 45

When the umbilical cord is wrapped around the fetal neck

Question 46

Answer 46

Think omphalomesenteric duct umbilical cyst

Note: Cyst in the periphery of the umbilical cord.

Question 47

What are the two major types of umbilical cord cyst?

Answer 47

• False cysts (more common)
• True cysts

Question 48

What are the most common true umbilical cysts?

Answer 48

• Omphalomesenteric duct cyst (more peripheral)
• Allantoic cyst (more central)

Question 49

Answer 49

Think allantoic umbilical cord cyst

Note: Cyst located centrally within the umbilical cord.

Question 50

Umbilical cord cysts are associated with…

Answer 50

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)