Placenta Praevia / Accreta and Vasa Praevia Flashcards Preview

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Flashcards in Placenta Praevia / Accreta and Vasa Praevia Deck (57)
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What is the incidence of placenta praevia?

1:200 (RCOG GTG)


What % of women with placenta praevia will have an APH during the course of their pregnancy?



What is the % risk of recurrence of placenta praevia?



What % of placenta praevias will resolve before delivery?



What are the risk factors for placenta praevia?

Obstetric risk factors:

  • Caesarean section (risk rises with number of prior CS)
  • Short interpregnancy interval (< 1 year) following CS
  • Elective/prelabour CS
  • Grand multiparity

Maternal factors:

  • Previous placenta praevia
  • Smoking
  • AMA
  • ART
  • Cocaine use
  • Previous uterine surgery
  • Ethnicity: Asian highest risk
  • Living at high altitudes

Fetal factors:

  • Male fetus
  • Multiple pregnancy



What is the definition of a placenta praevia?

Placenta lies directly over the internal os


What is the definition of a low-lying placenta?

Placental edge less than 20mm from the internal os on trans abdominal or transvaginal scanning (if > 16 weeks)


If a placenta praevia is present at 32/40, what % will resolve before term?



Describe the natural history of placental migration.

Natural history of placental migration:

  • Lower segment is 0.5 cm in size at 20 weeks and increases to >5 cm by term, causing migration of the stationary lower placental edge away from the cervical os.
  • Placenta-free uterine wall grows at a faster rate than uterine wall covered by placenta.
  • Trophotropism: growth of trophoblastic tissue away from cervical os towards fundus.



What factors are predictive of the presence of placenta praevia at delivery?

  • Lack of resolution of praevia by 32-35 weeks.
  • Placenta covering os by >25 mm
  • Posterior placenta
  • Previous CS


With placenta praevia, a short cervical length on TVS before 34/40 increases the risk of...

Preterm emergency delivery Antepartum haemorrhage Massive haemorrhage at CS


Regarding placenta praevia, list the effects on maternal and fetal morbidity and mortality:

Maternal effects:

  • APH
  • PPH
  • Postpartum hysterectomy
  • Blood transfusion
  • Maternal death
  • Amniotic fluid embolism

Fetal effects:

  • IUGR
  • Congenital anomalies
  • Preterm delivery
  • Perinatal death
  • NICU admission
  • Neonatal death
  • Malpresentation
  • Vasa praevia and velamentous cord insertion


Regarding low lying placenta:

What factors are considered when counselling about mode of delivery?

What factors will increase the risk of needing an emergency CS?

Factors to consider when deciding mode of delivery:

  • Clinical background
  • Maternal preference
  • Distance of placental edge from os.
  • Fetal head position relative to placental edge

Factors that increase the risk of emergency CS:

  • Placental edge <20 mm from os.
  • Placental edge thickness >10 mm
  • Presence of marginal sinus


When are steroids recommended in the context of placenta praevia?

Routinely (RCOG) Between 34+0 and 35+6/40


Is there any evidence for using cervical cerclage in the context of placenta praevia?



At what gestation should delivery be planned, for an uncomplicated placenta praevia?

What is the justification for this timing?

Between 36+0 and 37+0.

Risk of bleeding, labour or labour leading to emergency CS increases with advancing gestation:

  • Risk at 36 weeks 15%
  • Risk at 37 weeks 30%
  • Risk at 38 weeks 59%


At what gestation should delivery be planned, for a placenta praevia with a history of vaginal bleeding or other risk factors for preterm delivery?

Between 34+0 to 36+6/40


You are performing a Caesarean section for placenta praevia. After delivery of the placenta there is excessive bleeding and you are constantly needing to use the suction in order to see what you are doing.

What adjuncts could you use or perform in this scenario to help settle bleeding?

  • Oxytocics.
  • Placenta bed sutures using 2/0 vicryl:
    • Check what is behind the uterus to avoid injury to bowel, bladder etc.
    • A Deaver retractor in the uterine cavity is helpful to identify bleeding points.
  • Bakri ballon:
    • Most easily inserted from below.
    • Inflate and pull down; if this controls bleeding, deflate it and proceed to close the uterus and reinflate once uterus closed.
  • B-Lynch suture using 1 monocryl
  • Uterine artery ascending branch ligation:
    • Lies on broad ligament; find it by identifying round ligament first.



What is the incidence of placenta accreta spectrum?



What are the risk factors for placenta accreta spectrum?

  • Previous placenta accreta
  • Previous CS delivery (increasing risk with number of CS)
  • Previous uterine surgery including myomectomy, D&C, MROP
  • Placenta praevia
  • AMA
  • ART
  • Uterine pathology: bicornuate uterus, adenomyosis, submucous fibroids


What are the maternal complications associated with placenta accreta spectrum?

What are the fetal complications associated with placenta accreta spectrum?

  • Maternal complications:
    • Massive haemorrhage, multi-organ failure, maternal death.
    • Uterine rupture
    • Bladder injury: cystotomy, ureteric injury
  • Fetal complications:
    • Preterm birth


What can a CS scar ectopic evolve into?

Abnormally adherent or invasive placenta


Describe the pathogenesis of placenta accreta:

  • Nitabuch layer: a fibrinous layer at the junction between the decidua and cytotrophoblast.
    • Prevents excessive penetration of decidua by the trophoblast.
    • Is the layer at which separation of the placenta occurs.
  • Nitabuch layer is absent in placenta accreta.
    • Absence allows invasion and abnormal development of spiral arteries and intervillous spaces in the overlying placenta. 


What is the definition of placenta accreta?

Villi adheres superficially to the myometrium without interposing decidua


What is the definition of placenta increta?

Villi penetrate deeply into the uterine myometrium down to the serosa?


What is the definition of placenta percreta?

Villous tissue perforated through the entire uterine wall and may invade the surrounding pelvic organs, such as the bladder


What are the USS findings suggestive of placenta accreta? What is the sensitivity and specificity of diagnosisng accreta with ultrasound?

USS findings: -

  • Abnormality of the uterus-bladder interface (most specific sign 99.7%)
  • Placental lacunae
  • Increased vascularity of the placental bed with large feeder vessels entering the lacunae.
  • Loss of 'clear zone' / myometrium underneath placental bed.
  • Myometrial thinning overlying placenta <1 mm or undetectable.
  • Placental bulge: serosa appears intact but outline is distorted.
  • Focal exophytic mass: placental tissue breaking through uterine serosa and extending beyond it, often into bladder.


  • Sensitivity 90%
  • Specificity 96%


What are the MRI findings associated with placenta accreta?

  • Abnormal uterine bulging
  • Dark intraplacental bands on T2 weighted imaging
  • Heterogeneous signal intensity within the placenta
  • Disorganised vasculature of the placenta
  • Disruption of the uteroplacental zone


What are the six elements of care in the bundle recommended by RCOG / RCM for Placenta accreta spectrum?

1. Consultant obstetrician 2. Consultant anaesthetist 3. Blood and blood products available 4. MDT involvement in preoperative planning 5. Discussion and consent including possible interventions 6. ICU bed available


What are the surgical management options for placenta acreta and percreta?

  1. Delivery of baby and attempted delivery of placenta
  2. Delivery of baby via uterine incision distant from placenta, quick repair of uterus and en block hysterectomy.
  3. Delivery of the baby via uterine incision distant from the placenta, trimming of cord close to insertion site, full repair of uterus and conservative management.
  4. Delivery of baby without disturbing placenta, followed by partial excision of uterine wall (containing placental implantation site) and repair of uterus)
  5. Delivery of baby without disturbing the placenta, leaving placenta in situ, followed by elective secondary hysterectomy 3-7 days later.