30. Placenta previa. Other placental abnormalities

Question 1

what is placenta previa?

Answer 1

Abnormal implantation of the placenta over the internal cervical os.
The most common type of abnormal placentation
20% of cases of antepartum hemorrhage

Question 2

classification of placenta previa

Answer 2

1. complete
2. partial
3. marginal
4. low-lying placenta

Question 3

low-lying placenta

Answer 3

placenta is implanted in the lower uterine segment in close proximity (< 2 cm) to the internal os, but not extending

Question 4

complete previa

Answer 4

placenta completely covers the internal os.

Question 5

partial previa

Answer 5

placenta covers a portion of the internal os

Question 6

marginal previa

Answer 6

the edge of the placenta reaches the margin of the os

Question 7

risk factors of placenta previa

Answer 7

Multiparity
Increased maternal age
Prior placental disorders
Multiple gestation
Previous cesarean delivery
Previous D&C

Question 8

presentation of placenta previa

Answer 8

Painless 3rd trimester vaginal bleeding in a previously normal pregnancy

Question 9

diagnosis of placenta previa

Answer 9

Abdominal or transvaginal US.

Question 10

potential consequences of placenta previa

Answer 10

malpresentation, IUGR (placental insufficiency), vasa previa, PPROM

Question 11

treatment for asymptomatic previa

Answer 11

expectant management, measures to reduce the risk of bleeding, schedule cesarean delivery for 36-37 weeks gestation, consider antenatal corticosteroids (patients between 23-34 weeks)

Question 12

when do we do emergency cesarean delivery with placenta previa?

Answer 12

active labor, refractory life-threatening maternal bleeding, category III FHR tracing, and significant vaginal bleeding after 34 weeks gestation.

Question 13

what is done in case of low-lying placenta?

Answer 13

if distance from os < 10 mm schedule cesarean delivery
if distance from os 11-20 mm may perform vaginal delivery.

Question 14

speculum exam should be performed only after..

Answer 14

placenta previa is ruled out by abdominal US

Question 15

what is the definition of placenta accreta spectrum?

Answer 15

Abnormal attachment of the placenta (trophoblasts) through the uterine myometrium as a result of defective decidual formation.
sometimes the diagnosis is not made until delivery of the placenta.

Question 16

classification of placental accreta spectrum

Answer 16

• Placenta accreta (75%): anchoring villi attach to the myometrium (rather than decidua).
• Placenta increta (20%): anchoring placental villi penetrate into the myometrium.
• Placenta percreta (< 5%): anchoring placental villi penetrate through the myometrium to the uterine serosa or adjacent organs.

“Accreta Attaches,
Increta Invades,
Percreta Penetrates”.

Question 17

risk factors of placenta accreta

Answer 17

History of cesarean deliveries
History of uterine surgeries
Maternal age > 35 y’
Multiparity
History of pelvic radiation
History of endometritis

Question 18

how does placenta accreta present?

Answer 18

Profuse, life-threatening postpartum hemorrhage that occurs at the time of attempted manual placental separation.
May also present as antenatal bleeding in the setting of placenta previa.

Question 19

how is placenta accreta seen on US

Answer 19

multiple placental lacunae, loss of bladder line, loss of clear space, myometrial thinning, Doppler evaluation (abnormal vascularity, turbulent blood flow)

Question 20

when do we use MRI in placenta accreta?

Answer 20

evaluate for posterior placenta accreta, asses the degree of myometrial and parametrial involvement.

Question 20

when do we use MRI in placenta accreta?

Answer 20

evaluate for posterior placenta accreta, asses the degree of myometrial and parametrial involvement.

Question 21

what is the average blood loss at delivery in women with placenta accreta?

Answer 21

3-5 liters.

Question 22

what is done in case of placenta accreta?

Answer 22

1.- Scheduled cesarean hysterectomy- s considered the most reasonable and safest approach to management.
In a stable patient, plan the delivery for 34-36 weeks gestation.
2. Antenatal corticosteroids
3. Prevention of preterm delivery: pelvic rest, avoid pelvic exams, avoid sexual intercourse.
4. Management of PPH (in cases where placenta accreta wasn’t diagnosed before delivery).

Question 23

type 1 vasa previa

Answer 23

membranous vessels associated with a velamentous umbilical cord.

Question 24

type 2 vasa previa

Answer 24

membranous vessels connect the lobes of a bilobed placenta or the placenta and a succenturiate lobe (smaller accessory placental lobe that is separate from the main disc).

Question 25

what is the difference between the fetal blood vessles in vasa previa 1 and 2

Answer 25

in 1 they are surrounded only by fetal membranes, in the absence of protective wharton jelly
in 2 they are only supported by the chorioamniotic membranes

Question 26

presentation of vasa previa

Answer 26

Painless 3rd trimester vaginal bleeding that occurs after ROM.
Fetal distress (bradycardia and deceleration on tracing).

Question 27

how do we diagnose vasa previa?

Answer 27

1. Transabdominal or transvaginal US with doppler → fetal vessels overlying the internal os and decreased blood flow within fetal vessels.
2. Differentiate fetal vs maternal blood with the Apt test (alkaline denaturation test)

Question 28

what is a an Apt test?

Answer 28

blood sample from the vagina is mixed with distilled water to lyse RBC’s. Adding KOH results in yellowish-brown discoloration when the Hgb is maternal (denatured adult Hgb); fetal Hgb cannot be denatured by the KOH and the fluid remains red.

Question 29

when de we do an emergency cesaren delivery in vasa previa?

Answer 29

labor, PROM, non-reassuring fetal heart rate tracing

Question 30

antepartum management in vasa previa

Answer 30

corticosteroids at 28-32 weeks gestation
close fetal surveillance 30-34 weeks
scheduled cesarean delivery at 34-35 weeks gestation.