Abnormalities Of Placentation

Question 1

Occurs when the membranes double back over the edge of the placenta, forming a dense ring around the periphery of the placenta.

Answer 1

Circumvallate placenta

Question 2

Occurs when the placenta develops over the internal cervical os

Answer 2

Placenta previa

Question 3

Abnormal adherence of part of all of the placenta to the uterine wall

Answer 3

Placenta accreta

Question 4

Abnormal placentation in which the placenta invades the myometrium

Answer 4

Placenta increta

Question 5

Abnormal placentation in which the placenta invades through the myometrium to the uterine serosa

Answer 5

Placenta percreta

Question 6

Occurs when a velamentous cord insertion causes the fetal vessels to pass over the internal cervical os

Answer 6

Vasa previa

Question 7

Occurs when blood vessels insert between the amnion and the chorion, away from the margin of the placenta, leaving the vessels
largely unprotected and vulnerable to compression or injury

Answer 7

Velamentous placenta

Question 8

An extra lobe of the placenta that is implanted at some distance away from the rest of the placenta

Answer 8

Succenturiate placenta

Question 9

Often considered a variant of placental abruption, it is a major cause of second-trimester hemorrhage

Answer 9

Circumvallate placenta

Question 10

May be associated with a placenta in normal locations, but incidence increases in placenta previa

Answer 10

Placenta accreta

Question 11

Occasionally, placentas may invade into adjacent organs such as the bladder or rectum

Answer 11

Placenta percreta

Question 12

Occasionally, placentas may invade into adjacent organs such as the bladder or rectum

Answer 12

Placenta percreta

Question 13

Also seen with velamentous and succenturiate placentas

Answer 13

Vasa previa

Question 14

Fetal vessels may course between the two lobes, possibly over the cervix, leaving these blood vessels unprotected and at risk for rupture

Answer 14

Succenturiate placenta

Question 15

Of note, because many patients receive a routine obstetric ultrasound, marginal previa or low-lying placenta is commonly diagnosed in the _____________. This is diagnosed when the placental edge is ______ from, but not covering, the internal os.

Answer 15

second trimester; <2 cm

Question 16

Patients with placenta previa classically present with _________________.

Answer 16

sudden and profuse painless vaginal bleeding

Question 17

The first episode of bleeding in placenta previa—the “sentinel” bleed—usually occurs after __________ of gestation.

Answer 17

28 weeks

Question 18

_____________ is the premature separation of the normally implanted placenta from the uterine wall, resulting in hemorrhage between the uterine wall and the placenta.

Answer 18

Placental abruption (abruptio placentae)

Question 19

In 20% of placental separations, bleeding is confined within the uterine cavity and is referred to as a ________________.

Answer 19

concealed hemorrhage