Exxcellence pearls: placenta accreta

Question 0

Define placenta accreta, increta, and percreta.

Answer 0

Abnormal attachment to the myometrium with adherence to the myometrium, invasion of the myometrium, or perforating through the myometrium.

Question 1

What is the cause of placenta accreta?

What is the incidence of placenta accreta?

Answer 1

Abnormal or absent decidual formation at placental implantation. Specifically imperfect development of the fibrinoid or Nitabuch’s layer.

1/500-2500.

Question 3

What are risk factors for abnormal placentation?

Answer 3

Placenta previa, previous cesarean delivery, multigravity, older pregnant women, previous curettage, previous uterine sepsis or manual placenta extraction, leiomyomata, uterine perforation, prior abortion, and endometrial ablation.

Question 4

How is placenta accreta diagnosed histologically?

Answer 4

Absence of the decidua basalis which is replaced by this connective tissue.

Question 4

What percentage of low-lying placentas will migrate away from the cervix by term?

Answer 4

90%

Question 5

What ultrasound findings are suspicious for placenta accreta?

Answer 5

Blurring of the normal placenta-uterine wall boundary, absence of subplacental hypoechoic zone, presence of lacunar bloodflow patterns or “moth-eaten” appearance.

Question 6

When should delivery be performed?

Describe delivery management for expected placenta accreta.

Answer 6

At least 34 weeks after antenatal steroids but timing should be individualized.

Preparations should be made for hysterectomy, including anesthesia, instruments, and adequate blood. Coagulopathy secondary to blood loss and replacement is common. If myometrial invasion is minimal and the bladder is spared, conservative management with uterine packing maybe possible.

Question 7

What are the major risks of excessive cord traction in the setting of placenta accreta?

Answer 7

Uterine rupture or inversion.

Question 8

What is the rate of maternal mortality with peripartum hysterectomy for placenta accreta?

And with conservative management?

Answer 8

2-6%

Up to 30%

Question 9

What is the risk of placenta accreta in the setting of placenta previa with one prior cesarean section?
Two prior?
Three prior?
Four prior?

What is the risk of placenta accreta with placenta previa and no prior cesarean section?

Answer 9

3%
11%
40%
61%

1-5%

Question 10

What is the average estimated blood loss for placenta accreta?

What is the average amount of transfused units of RBCs?

Answer 10

2500-5000 ml

5-10 units

Question 11

What additional steps should be considered for the management of placenta accreta in a patient who refuses blood transfusion?

Answer 11

Transfer to maternal fetal medicine
Consider IV iron or darbepoetin (synthetic EPO)
Arterial and central venous lines
Iliac balloons
Cell saver
Gyn onc assistance