Placenta Previa 2013

7/30/2019 Placenta Previa 2013

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Placenta previa (PP)

I. Placenta previa (PP) is defined as

the presence of placental tissue over ornear the internal cervical os.

PP can be classified into

four types based on the location of the placenta relative to

the cervical os:

to the internal os.


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complete or total previa,

the placenta covers the entire

cervical os; partial previa,

the margin of the placenta coverspart but not all of the internal os;

marginal previa,

the edge of the placenta liesadjacent to the internal os;

low-lying placenta, placenta is located near (2 to 3 cm)

but not directly adjacent


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A. Epidemiology

1. the incidence of PP is 1 in 200 to 1 in 390

pregnancies over 20 weeks' gestational age).varies with parity,

For nulliparous, the incidence is 0.2%,

in grand multiparous, it may be as high as 5%2. The most important risk factor for PP is aprevious cesarean section.

PP occurs in 1% of pregnancies after a

cesarean section.The incidence after four or more cs increasesto 10%


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3. Other risk factors

increasing maternal age after age 40),

multiple gestation, and previousuterine curettage

4. the placenta covers the cervical os

in 5% of pregnancies when examinedat midpregnancy.

The majority resolve as the uterusgrows with gestational age.

The upper third of the cervix developsinto the lower uterine segment, and

the placenta "migrates" away from theinternal os.


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B. Etiology. unknown.

a. Endometrial scarring.

b. A reduction inuteroplacental oxygenpromotes need for an increasein the placental surface areathat favors previa places.


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2. Bleeding occur in association with

the development of the lower uterine

segment in the third trimester.

Placental attachment is disrupted

because this area gradually thins in

preparation for labor.


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the thinned lower uterine segment is

unable to contract adequately to

prevent blood flow from the openvessels.shearing action

3. Vaginal examination or

intercourse may also cause separationof the placenta from the uterine wall.


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C. Clinical Manifestations

1. 80% of affected patients presentwith painless vaginal bleeding

Most commonly,

the first episode is around 34 weeks ofgestation;

one-third of patients develop bleedingbefore 30 weeks


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2. 30% patients develop bleedingafter 36 weeks,

10% go to term without any bleeding

The fluid is usually bright red,

and the bleeding is acute in onset.

3. The number of bleeding episodes is

unrelated to the degree of placentaprevia or

the prognosis for fetal survival.


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4. pp is associated with a doubling ofthe rate of congenital malformations.

a. CNS, GI tract, cardiovascularsystem, and respiratory system

b. Pp is also associated with

fetal malpresentation, preterm premature rupture of

membranes, and

intrauterine growth restriction.


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c. Abnormal growth of the placentainto the uterus can result in one of thefollowing 3 complications:

i. Placenta Previa Accreta.

The placenta adheres to the uterinewall without the usual interveningdecidua basalis.

The incidence in patients with previawho have not had previous uterine

surgery is 4%. The risk is increased 25%

in patients who have had a previous

cs or uterine surgery


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ii. Placenta Previa Increta.

placenta invades myometrium.

iii. Placenta Previa Percreta.

The placenta penetrates the

entire uterine wallgrowing into bladder or bowel.


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D. Diagnosis

1. History.

PP presents with acute onset ofpainless vaginal bleeding.

A thorough history should be obtained

from the patient, including obstetricand surgical history as well asdocumentation of previous ultrasoundexaminations.

Other causes of vaginal bleeding mustalso be ruled out, such as placentalabruption.


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2. Vaginal sonography is the goldstandard for diagnosis of previa

Placental tissue has to be overlying orwithin 2 cm of the internal cervical os tomake the diagnosis.

The diagnosis may be missed bytransabdominal scan,

if the placenta lies in the posteriorportion

empty bladder may help in identifyinganterior previas, and

Trendelenburg positioning may be

useful in diagnosing posterior previas.


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3. Examination. IfPP is present, digitalexamination is contraindicated.

a. A speculum examination can beused to evaluate the

b. Maternal vital signs,

abdominal exam, uterine tone, and

fetal heart rate monitoring should beevaluated.


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E. Management

1. Standard Management

a. In the third trimester in a patient whois not bleeding,

recommendations include

ultrasound confirmation

pelvic rest (nothing in the vagina,including intercourse or pelvic exams),

explanation of warning signs and when toseek immediate medical attention,

avoidance of exercise and strenuousactivity,

and fetal growth ultrasounds every 3 to 4weeks.

Fetal testing semiweekly

b S d d f


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b. Standard management ofsymptomatic patients with PP

hos-pitalization with hemodynamic

stabilization and

continuous maternal and fetalmonitoring.

Laboratory studies should be ordered Steroids should be given to promote

lung maturity for gestations between

24 and 34 weeks. Rho(D) immunoglobulin should be

administered to Rh-neg-ativemothers.


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2. Term Gestation, Maternal andFetal Hemodynamic Stability.

At this point, management dependson placental location.

a. Complete Previa.

Patients with complete previa atterm require cesarean section.


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3. Term Gestation,

Maternal and Fetal

Hemodynamic Instability. The first priority is to stabilizethe mother with

fluid resuscitation and administration of bloodproducts, if necessary.

Placenta Previa 2013

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