•The Latin word previa means going
before, and in this sense, the placenta goes
•before the fetus into the birth canal.
•Definition- When the placenta is
implanted partially or completely over the
lower uterine segment (over and adjacent
to the internal cervical os) it is called
•There are multiple types
• Dropping down theory - The
fertilized ovum drops down and is
implanted in the lower segment. Poor
decidual reaction in the upper uterine
segment may be the cause
• Persistence of chorionic activity
• Defective decidua- results in spreading
of the chorionic villi over a wide area
in the uterine wall to get nourishment.
• Big surface area of the placenta- in
twins may encroach onto the lower
•There are four types of placenta
praevia depending upon the degree
of extension of placenta to the
• Type 1 (Low lying)
• Type 2 (Marginal)
• Type 3 ( Incomplete or partial
• Type 4 ( Central or total)
Low lying Placenta Previa
The placenta implants in the lower uterine segment but does not reach
the cervical os; often this type of placenta previa moves upward as the
pregnancy progresses, eliminating bleeding complications later
Marginal Placenta Previa
The edge of the placenta is at the edge of the internal os; the mother
may be able to deliver vaginally.
Partial or Incomplete Placenta Previa
The placenta partially covers the cervical os;as the pregnancy
progresses, the cervix begins to efface and dilate, then bleeding occurs
Central or Total
The placenta covers the entire cervical os; usually requires an
emergency cesarean section.
•For clinical purpose, the types are graded into
• mild degree (Type-I and II anterior) and
• major degree (Type-II posterior, III and IV).
•Dangerous placenta previa
•is the type- II posterior placenta previa because
• Placenta is more likely to be compressed, if
vaginal delivery is allowed
• More chance of cord compression or cord
• Increased maternal age (> 35
• History of previous cesarean
section or any other scar in the
• Placental size and abnormality
• The only symptom of placenta previa
is vaginal bleeding which is sudden
onset, painless, bright red apparently
causeless and recurrent
• The bleeding is unassociated with pain
unless labor starts simultaneously.
• In placenta previa, the blood is
bright red as the bleeding occurs
from the separated uteroplacental
sinuses close to the cervical opening
and escapes out immediately
• Placenta—The placenta may be large
and thin. There is often a tongue-
shaped extension from the main
• Umbilical cord—The cord may be
attached to the margin (battledore) or
into the membranes (velamentous).
• Lower uterine segment—Due to
increased vascularity, the lower uterine
segment and the cervix becomes soft
and more friable
• The size of the uterus proportionate
to the period of gestation
• The uterus feels relaxed, soft and
elastic without any localised area of
• Persistence of malpresentation
• Head is floating in contrast to the
period of gestation.
• Fetal heart sound
• Stallworthy’s sign
•MATERNAL: During pregnancy
• Antepartum hemorrhage with varying
degrees of shock is an inevitable
• Malpresentation: increased incidence
of breech presentation and transverse
lie. The lie often becomes unstable.
• Premature labor either spontaneous or
induced is common
• Death due to massive hemorrhage
• Adequate antenatal care
• Antenatal diagnosis
• Warning haemorrhage should not be ignored
•The aim is to continue pregnancy for fetal maturity without
hurting mothers health
• Availability of blood for transfusion whenever required
• Bed rest
• Bleeding occurs at or after 37 weeks of
• Patient is in labour
• Patient is exsanguinated state on
• Bleeding is continuing and of moderate
• Baby is dead or known to be
•Cesarean delivery is done for all
women with sonographic evidence of
placenta previa where placental edge is
within 2 cm from the internal os. It is
especially indicated if it is posterior or
•Vaginal delivery may be considered
where placenta edge is clearly 2–3 cm
away from the internal cervical os
in the decidua capsularis and its subsequent development into capsular placenta which comes in contact with decidua vera of the lower segment can explain the formation of lesser degrees of placenta previa.
(1) Because of the curved birth canal major thickness of the placenta (about 2.5 cm) overlies the sacral promontory, thereby diminishing the anteroposterior diameter of the inlet and prevents engagement of the presenting part. This hinders effective compression of the separated placenta to stop bleeding.
3-(myomectomy or hysterecotomy)
5-Smoking — causes placental hypertrophy to compensate carbon monoxide induced hypoxemia
As the placental growth slows down in later months and the lower segment progressively dilates, the inelastic placenta is sheared off the wall of the lower segment.
This leads to opening up of uteroplacental vessels and leads to an episode of bleeding.
As it is a physiological phenomenon which leads to the separation of the placenta, the bleeding is said to be inevitable.
However, the separation of the placenta may be provoked by trauma including vaginal examination, coital act, external version or during high rupture of the membranes.
The blood is almost always maternal, although fetal blood may escape from the torn villi especially when the placenta is separated during trauma.
Placenta—The placenta may be large and thin.
Slowing of the fetal heart rate on pressing the head down into the pelvis which soon recovers promptly as the pressure is released is suggestive of the presence of low lying placenta especially of posterior type (Stallworthy’s sign).
Vulval inspection: Only inspection is to be done to note whether the bleeding is still occurring
Vaginal examination must not be done outside the operation theater in the hospital, as it can provoke further separation of placenta with torrential hemorrhage and may be fatal.
Malpresentation: The lie often becomes unstable.
Death due to massive hemorrhage during the antepartum, intrapartum or postpartum period
Cord prolapse due to abnormal attachment of the cord
Slow dilatation of the cervix due to the attachment of placenta on the lower segment.
Intrapartum hemorrhage due to further separation of placenta with dilatation of the cervix.
Low birth weight babies are quite common which may be the effect of preterm labor either spontaneous or induced.
Asphyxia is common and it may be the e#ect of — (a) early separation of placenta (b) compression of the placenta or (c) compression of the cord
Intrauterine death is more related to severe degree of separation of placenta, with maternal hypovolemia and shock. Deaths are also due to cord accidents
Birth injuries are more common due to increased operative interference.
Congenital malformation is three times more common in placenta previa.
Maternal and fetal morbidity and mortality from placenta previa are significantly high.
A gentle speculum examination after bleeding
Use of tocolysis if contractions
The expectant treatment is carried up to 37 weeks of pregnancy. By this time, the baby becomes sufficiently mature
However, preterm delivery may have to be done in conditions, such as:
(1) Recurrence of brisk hemorrhage and which is continuing.
(2) The fetus is dead.
(3) The fetus is found congenitally malformed on investigation.