Placenta previa

1. WHAT IS PLACENTA PREVIA?

It is a condition in pregnancy where the placenta is abnormally located (located over or very near the internal os)

2. WHAT ARE THE TYPES OF PREVIA?

Four Types or Degrees

totalis – internal cervical os is totally covered

partialis – internal os is partially covered

marginalis – edge of placenta is at the margin of the internal os

low-lying placenta – placenta is implanted in the lower uterine segment such that the placental edge actually does not reach the internal os

3. WHAT IS VASA PREVIA?

Is a condition where there is abnormal insertion of umbilical cord

velamentous insertion when some of the fetal vessels in the membranes cross the region of the cervical os below the presenting fetal part

membrane rupture accompanied by tearing of fetal vessel causes the bleeding

4. WHAT CAUSES PLACENTA PREVIA

advancing maternal age

multiparity

multiple gestation (40%)

prior caesarean delivery (risk inc. progressively as parity and number of prior CS deliveries inc. (8 fold with parity > 4 and >4 prior CS)

smoking: CO hypoxemia/placental hypertrophy

5. WHAT ARE COMPLICATIONS ARISING FROM THE CONDITION?

preterm delivery is a major cause of perinatal death

fetal growth restriction even with term infants (decidualization of lower segment not as good as upper segment)

fetal anomalies

6.WHAT ARE THE THE SIGNS AND SYMPTOMS?

painless bleeding without warning near the end of the 2nd trimester or after

initial bleeding rarely profuse and ceases spontaneously only to recur (good prognosis, you can opt not to deliver right away)

causes of hemorrhage:

formation of the lower uterine segment and dilatation of the internal os resulting in tearing of the placental attachments

bleeding may be augmented by the inherent ability of the myometrial fibers of the lower uterine segment to contract and constrict the torn vessels so it may continue even after delivery of the placenta

associated with placenta accreta, increta, or percreta because of the poorly developed decidua in the lower uterine segment

coagulopathy is rare even with extensive separation from the implantation site – thromboplastin escapes thru the cervical canal rather than beng forced into maternal circulation

7. HOW DO WE DIAGNOSE?

AVOID INTERNAL EXAM

simplest, most precise and safest method is transabdomninal ultrasound

improved diagnostic accuracy with transvaginal ultrasound (visualization of the internal os)

the concept of placental migration:

movement? No, never had actual circumferential villus invasion that reached the internal cervical os

placenta that lie close to the internal os, but not over it, during the 2nd trimester or early 3rd trim are unlikely to present as previas by term

likelihood that placenta previa persists after ultrasound diagnosis before 28 wks is greater in woman who had a prior CS delivery

8. HOW IS PLACENTA PREVIA MANAGED?

Delivery is done via caesarean section – transverse vs vertical is dependent on whether the lower segment is well formed, location of the placenta anteriorly or posteriorly and whether the baby is in transverse position or not

preterm fetus with no active bleeding = expectant management (hospital vs home), bedrest, give steroids for lung maturity of baby, try to bring as close to term as possibe

profuse bleeding, term = delivery

bleeding over implantation site on delivery = oversewing, packing, bilateral uterine or internal iliac ligation, hysterectomy if conservative management not possible

placenta previa implanted anteriorly over a previous scar with inc. likelihood of accreta = hysterectomy