Placenta Previa

Question 1

Definition of placenta previa

Answer 1

abnormal implantation of placenta over the internal cervical os

Question 2

Complete previa

Answer 2

placenta completely covers internal cervical os

Question 3

Partial previa

Answer 3

placenta covers portion of internal cervical os

Question 4

Marginal previa

Answer 4

edge of placenta reaches margin of the internal cervical os

Question 5

Low-lying placenta

Answer 5

placenta that is implanted in the lower uterine segment close proximity but not reaching margin of the os

Question 6

Vasa previa

Answer 6

fetal vessel covering cervix d/t atrophy of a placental segment overlying the less well vascularized cervix when a velamentous cord insertion passes over cervical os

Question 7

What is the probable reason that 90% of low-lying placentas appear to move away from the cervix and out of the lower uterine segment?

Answer 7

d/t development of lower uterine segment and trophotropism (growth preferentially toward a better vascularized fundus)

Question 8

Succenturiate lobe

Answer 8

an incomplete atrophy of a segment of the placenta that leaves a placental lobe discrete from the rest of the placenta

Question 9

What is the estimate of maternal mortality in cases of placenta previa?

What is the cause (and %) of most perinatal deaths in this situation?

Answer 9

0.03%

Premature delivery is responsible for 60% of perinatal deaths

Question 10

What are fetal complications associated with placenta previa?

Answer 10

preterm delivery (and its complications)
PPROM (and its complications)
IUGR
Malpresentation
Vasa previa
Congenital abnormalities

Question 11

Placenta acreta

Average blood loss?

Sequelae?

Answer 11

superficial attachment of the placenta to uterine myometrium (increased incidence in placenta previa)

3-5 L average blood loss

hemorrhage and shock –> hysterectomy, surgical injury to ureters/bladder/viscera, ARDS, renal failure, coagulopathy, death, spontaneous uterine rupture (2T, 3T) –> intraperitoneal hemorrhage

Question 12

Placenta increta

Answer 12

placental invasion of the myometrium (but not through)

Question 13

Placenta percreta

Answer 13

placenta invasion through myometrium into the uterine serosa

Question 14

What is historically the most frequent indication for peripartum hysterectomy?

What about now?

Answer 14

Historically, Uterine atony

Now, abnormal placentation/placenta accreta

Question 15

Velamentous placenta

Answer 15

occurs when blood vessels insert between amnion and chorion away from margin of placenta, leaving vessels vulnerable to compression/injury

Question 16

How often does placenta previa occur?

Answer 16

1:200 births

Question 17

In what % of women does placenta previa occur in women with prior C-sections?

Answer 17

1-4% of women with prior C-sections

Question 18

How often does placenta accreta complicate placenta previa?

Answer 18

5% of cases

Question 19

Placenta increases by ___ % in the setting of:

1 prior C-section
2 prior C-sections
3+ prior C-sections

Answer 19

1) 15-30%
2) 25-50%

3+) 29-67%

Question 20

Predisposing factors for placenta previa

Answer 20

Prior C-section/Uterine surgery/Prior uterine scars
Multiparity
Multiple gestation
Erythroblastosis
Smoking
Hx placenta previa
Increased maternal age

Question 21

Classical S&S

Answer 21

sudden, profuse PAINLESS vaginal bleeding

Question 22

Sentinel bleed

What is it?
When does it occur?

Answer 22

first episode of bleeding

generally after 28 wks GA

Question 23

On physical exam, is vaginal examination warranted?

Answer 23

No. Vaginal exam is contraindicated in previa because digital examination can cause further separation and trigger hemorrhage.

Question 24

What is the sensitivity of US for diagnosis of placenta previa?

What method is preferred?

Answer 24

95%

transvaginal US

Question 25

Why should a bladder be empty before doing a transabdominal US to check for placenta previa?

Answer 25

Bladder can compress lower uterine segment –> “longer” cervix, normal placenta can look like previa

Question 26

What is the general treatment for stable asymptomatic pts?

Answer 26

Bed rest and no intercourse

Question 27

What are indications for immediate C-section in the setting of placenta previa?

Answer 27

Unstoppable labor
Fetal distress
Life-threatening Hemorrhage
Placental edge

Question 28

For patients with placenta previa who make it to 36 weeks, what does typical management involve?

Answer 28

Amniocentesis (to determine fetal lung maturity). If no lung maturity, elective C-section at 38 wks without repeating amniocentesis
C-section between 36-37 wks (after confirmed fetal lung maturity)

Question 29

What is the course of action in the case of vaginal bleeding and suspected placenta previa?

What if suspected accreta/increta/percreta?

Answer 29

1. Stabilize pt. (Hospitalize, continuous fetal monitoring, IV access, Hct, Type and Cross, PT/PTT/D-dimer/Fibrin Split Products, Fibrinogen, Kleihaur-Betke for RhNeg)
2. Prepare for catastrophic hemorrhage (Hospitalization, Bed rest, Hct monitoring, 2+ U of blood should be Type&Cross, Cross-matched and available –> Transfusions are given to maintain Hct of 25 or greater)
3. Prepare for Preterm delivery (Give Steroids to women between 24-34 wks to promote fetal lung maturity. Neonatal consultation. US to r/o accreta. Before 32 wks, mod bleeding w/o fetal compromise –> blood transfusion management. Cautious Tocolytics to try to prolong up to 34 wks)

1. Plan for TAH at the time of C-section (Leave placenta in place.
2. Schedule delivery at 34-37 wks (Elective hysterectomy decreases risk of intraoperative blood loss compared to emergency hysterectomy)
3. Plan ahead and have backup available (Counsel pt. regarding hysterectomy and blood transfusion. T&C blood.)