PLACENTA PREVIA
Definition:
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Placenta previa: Abnormal location of the placenta over ,or in close proximity to the
internal os.
Incidence:
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Approximately 1/250 pregnancy.
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Nulliparas: 1/1000~1/1500 pregnancy.
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Grandmultiparas: 1/20.
Classification:
1. Complete (total) placenta previa: Entire cervical os is covered.
2. Partial placenta previa: The margin of the placenta extends across but not all of
the internal os.
3. Marginal: Edge of the placenta lies adjacent to the internal os.
4. Low lying placenta: Placenta is located near but not directly adjacent to the
internal os.
Etiology:
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Mechanism: abnormal vascularization.
Predisposing factors:
• Twin pregnancy.
• Increasing maternal age.
• Increasing parity.
• Previous cesarean section.
Diagnosis:
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Painless vaginal bleed: first bleeding episode is 29~30 weeks
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Ultrasonography: benefit in localizing the placenta and diagnosis placenta previa
Caution:
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Double setup vaginal examination.
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No digital vaginal or rectal examination is preformed in case of placenta previa.
Only as a final and definitive event and only under conditions of double set up.
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This procedure involves careful evaluation of the cervix in the operation room
with full preparations for rapid cesarean section.
Management:
Basic management:
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Initial hospitalization with hemodynamic stabilization
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Enforced bed rest
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Restrictions of activity
Expectant management: (allow for further fetal growth and maturation):
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Blood transfusion is given as necessary.
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Amniocentesis for fetal lung maturity testing.
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Cesarean birth if fetus is thought to be mature.
Indication of vaginal delivery:
1. Delivery can be accomplished with minimal blood loss
2. Fetus is dead
3. Major fetal malformation
Complications:
1. Placenta previa accreta
2. Postpartum hemopphage
3. Increasing maternal mortality and perinatal mortality
VASA PREVIA:
Definition:
•
Vasa previa refers to fetal vessels running through the membranes over the cervix
and under the fetal presenting part, unprotected by placenta or umbilical cord.
•
The condition usually results either from a velamentous insertion of the cord into
the membranes rather than the placenta or from vessels running between lobes of
a placenta with one or more accessory lobes.
Clinical Importance:
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Vasa previa is a condition which, undiagnosed, is associated with a perinatal
mortality of approximately 60%.76 The condition is important because, when the
membranes rupture, spontaneously or artificially, the fetal vessels running through
the membranes have a high risk of concomitant rupture, frequently resulting in fetal
exsanguinations and death.
•
Because the fetal blood volume is only about 80–100 mL/kg, loss of even small
amounts of blood could prove disastrous to the fetus. Pressure on the unprotected
vessels by the presenting part could lead to fetal asphyxia and death.