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Abnormal placentation > Placenta Praevia / Accreta and Vasa Praevia > Flashcards

Placenta Praevia / Accreta and Vasa Praevia Flashcards

1
Q

What is the incidence of placenta praevia?

A

1:200 (RCOG GTG)

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2
Q

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

A

70-80%

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3
Q

What is the % risk of recurrence of placenta praevia?

A

4-8%

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4
Q

What % of placenta praevias will resolve before delivery?

A

90%

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5
Q

What are the risk factors for placenta praevia?

A

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
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6
Q

What is the definition of a placenta praevia?

A

Placenta lies directly over the internal os

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7
Q

What is the definition of a low-lying placenta?

A

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

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8
Q

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

A

50%

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9
Q

Describe the natural history of placental migration.

A

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.
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10
Q

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

A
  • Lack of resolution of praevia by 32-35 weeks.
  • Placenta covering os by >25 mm
  • Posterior placenta
  • Previous CS
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11
Q

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

A

Preterm emergency delivery Antepartum haemorrhage Massive haemorrhage at CS

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12
Q

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

A

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
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13
Q

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?

A

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
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14
Q

When are steroids recommended in the context of placenta praevia?

A

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

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15
Q

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

A

No

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16
Q

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

What is the justification for this timing?

A

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%
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17
Q

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

A

Between 34+0 to 36+6/40

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18
Q

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?

A
  • 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.
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19
Q

What is the incidence of placenta accreta spectrum?

A

1:300-2000

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20
Q

What are the risk factors for placenta accreta spectrum?

A
  • 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
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21
Q

What are the maternal complications associated with placenta accreta spectrum?

What are the fetal complications associated with placenta accreta spectrum?

A
  • Maternal complications:
    • Massive haemorrhage, multi-organ failure, maternal death.
    • Uterine rupture
    • Bladder injury: cystotomy, ureteric injury
  • Fetal complications:
    • Preterm birth
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22
Q

What can a CS scar ectopic evolve into?

A

Abnormally adherent or invasive placenta

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23
Q

Describe the pathogenesis of placenta accreta:

A
  • 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.
24
Q

What is the definition of placenta accreta?

A

Villi adheres superficially to the myometrium without interposing decidua

25
Q

What is the definition of placenta increta?

A

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

26
Q

What is the definition of placenta percreta?

A

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

27
Q

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

A

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%
28
Q

What are the MRI findings associated with placenta accreta?

A
  • 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
29
Q

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

A
  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
30
Q

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

A
  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.
31
Q

Should Methotrexate be used for placenta accreta which is managed expectantly?

A

No Unproven benefit Significant adverse effects

32
Q

At what gestation should delivery be planned for placenta accreta spectrum?

A

35+0 to 36+0 In the absence of risk factors for preterm delivery

33
Q

Regarding placenta accreta:

Describe your antenatal, intrapartum and postnatal management to reduce the risk of massive blood loss:

A
  • Antenatal:
    • Optimise Hb and iron stores antenatally.
    • Safe disposition: close to hospital of planned confinement for 3rd trimester.
    • ?Radiological balloon catheters prior to delivery.
  • Intrapartum:
    • Planned elective Caesarean section-hysterectomy at earlier gestation.
    • Consent for massive blood transfusion
    • Consent for hysterectomy
    • Blood group and cross match.
    • Delivery at a centre with:
      • Blood bank able to perform massive transfusion protocol.
      • Haematology service.
      • Vascular surgery service
      • Interventional radiology service.
    • Use cell-saver.
  • Postnatal:
    • Admission to ICU/HU.
    • Interventional radiology input.
    • Debriefing: what happened, whyt it happened, implications for future pregnancy and fertility, risk of recurrence if conservative management successful.
34
Q

Regarding placenta accreta spectrum:

Outline your antenatal and intrapartum management to address the issue of placental invasion of surrounding structures (percreta):

A
  • Antenatal:
    • Diagnostic imaging with appropriate expertise in diagnosising percreta.
  • Intrapartum:
    • Delivery at a centre with:
      • Urology service
      • General surgery service.
    • Pre-op cystoscopy and insertion of ureteric stents especially if bladder involvement.
    • Planned cystotomy: can prevent extensive damage and bleeding from attempts at dissection.
35
Q

Regarding placenta accreta spectrum:

Outline your antenatal and intrapartum management for anaesthesia:

A
  • Antenatal:
    • Antenatal discussion with anaesthetist.
    • Involvement of senior anaesthetist in planning.
  • Intrapartum:
    • Regional anaesthesia safe but may need to convert to GA.
36
Q

Regarding placenta accreta spectrum:

If conservative management is successful, what is the prognosis for:

  • Fertility rates
  • Recurrence of placenta accreta
A
  • Fertility rates and pregnancy outcomes: good.
  • Recurrence rate of placenta accreta increased: 17-29%
37
Q

What is the incidence of vasa praevia?

A

1:2500 (RANZCOG)

38
Q

What is the definition of vasa praevia?

A

Exposed fetal vessels which run through the free placental membranes, and they cover or are in close proximity to the internal cervical os

39
Q

Why are fetal vessels at risk of rupture in vasa praevia?

A

Fetal vessels are unprotected by placental tissue or Wharton’s jelly of the umbilical cord.

Can rupture in active labour or when rupture of membranes occurs.

Total fetal blood volume only 80-100 mL/kg so fetus can rapidly exsanguinate.

40
Q

What is a Type I Vasa praevia?

A

Velamentous insertion of the umbilical cord into the placenta

41
Q

What is a Type II Vasa Praevia?

A

Membranous fetal vessels connecting the lobes of a bilobed placenta or placenta and a succenturiate lobe

42
Q

What are the risk factors for vasa praevia?

A
  • Velamentous cord insertion
  • Succenturiate lobe / bi-lobed placenta
  • Placenta praevia
  • History of low-lying placenta in second trimester
  • IVF pregnancy
  • Multiple pregnancy
43
Q

What is the fetal blood volume at term?

A

80-100mL / kg (RANZCOG Vasa Praevia guideline)

44
Q

What is the recommendations for screening in the context of Vasa Praevia?

A

Insufficient evidence for universal TVUSS screening as:

  • No robust evidence it is accurate, practical or improves perinatal oiutcomes.
  • TVUSS is acceptable to some patients.
  • Not cost effective.

Universal screening of lower placental edge and cord insertion with TAUSS is recommended:

  • No further action if edge >2 cm from os.
  • Attempt TA colour doppler of cervix if risk factors for vasa praevia.
  • Proceed to targeted TVUSS is suspicious findings or poor visuslisation.
45
Q

What is the incidence of velamentous placental cord insertion in singleton pregnancies?

A

1%

46
Q

What proportion of velamentous placental cord insertions are complicated by vasa praevia?

A

2%

47
Q

Approximately how many of the cases of vasa praevia occur in the setting of a velamentous cord insertion?

A

50%

48
Q

What is the survival rate if vasa praevia is diagnosed antenatally, vs intrapartum?

What is the rate if infant blood transfusion if vasa praevia is diagnosed antenatally?

A

Survival rate if vasa praevia diagnosed antenatally = 97% vs intrapartum = 44%

Rate of infant blood transfusion 3.4% (diagnosed antenatally) vs 58%

RANZCOG

49
Q

How can vasa praevia present Intrapartum?

A

Painless dark red vaginal bleeding (Benckiser’s haemorrhage) and Acute fetal compromise (tachycardia, bradycardia, sinusoidal) Particularly after SROM / ARM

50
Q

At what gestation should delivery of women with vasa praevia be considered?

A

34-36/40

51
Q

At what gestation should women with vasa praevia be admitted to hospital?

A

30/40 (RANZCOG) Weak evidence, poor quality RCOG qualifies this by saying other factors should be taken into account - multiple pregnancy, antenatal bleeding, TPTL

52
Q

When should corticosteroids be given in the context of vasa praevia?

A

32/40 (RANZCOG and RCOG)

53
Q

What are the maternal and fetal effects of vasa praevia?

A

Maternal effects:

  • Maternal anxiety

Fetal effects:

  • Perinatal mortality
  • IUGR
  • Preterm birth
  • Neonatal blood transfusion
  • MC twins with type I vasa praevia: discordant growth, IUGR and TTTS
54
Q

What are the ultrasound findings diagnostic of vasa praevia?

What is the sensitivity and specificity of TVUSS in the diagnosis of vasa praevia?

A
  • Aberrant linear or tubular echolucent structures with 2D imaging.
  • Demonstrating blood flow in these structures using colour or power doppler.
  • Demosntrating umbilical arterial/venous doppler waveforms using pulse wave doppler.
  • Aberrant vessels located over or within 2 cm of internal os attached to inner perimeter of the fetal membranes

Sensitivity: 100%

Specificity 99%

55
Q

What issues may there be in diagnosing vasa praevia with TVUSS?

What are the differential diagnoses for blood vessels seen near the cervix and how can they be differentiated from vasa praevia?

A

Issues with diagnosising vasa praevia on TVUSS:

  • Direction of fetal vessels may inhibit diagnosis.
  • False positives may occur due to:
    • Motion artefact
    • Umbilical cord presentation
    • Marginal placental sinus

Differential diagnoses:

  • Funic (cord) presentation: vessels are surrounded by Wharton’s jelly and can float away from the cervical os.
  • Cervico-uterine vessels: pulsed doppler will demonstrate fetal heart rate different from that in vessels.
  • Amniotic band or chorioamniotic separation: colour doppler will not demonstrate blood flow.
  • Cervical varicosity (rare): vessels do not pass across the os, are tortuous and may be part of a venous plexus.
56
Q

Outline your management of an asymptomatic woman with vasa praevia diagnosed antenatally:

A
  • General advice: avoid sexual intercouse, strenuous activity/exercise, digital vaginal exams.
  • Admit from 30 weeks until delivery.
    • Outpatient management may be consiered in some women if long closed cervix on serial TVUSS and negative fFN.
  • Corticosteroids from 32 weeks.
  • Delivery by elective CS between 34-36 weeks.
    • Consider TVUSS with colour doppler to map fetal vessels pre-op.
57
Q

Outline your management of a symptomatic woman with previous undiagnosed vasa praevia:

A
  • Suspect undiagnosed vasa praevia if:
    • Fresh vaginal bleeding +/- membrane rupture AND
    • Acute fetal compromise: progressive tachycardia, prolonged bradycardia, sinusoidal pattern OR
    • Fetal death
  • Delivery by urgent emergency CS: do not delay delivery to confirm diagnosis.
  • Inform paediatrician of suspicion and need to bring O Rh negative blood for transfusion.
  • Placental pathological examination to confirm diagnosis of vasa praevia especially if stillbirth or acute fetal compromise.

Abnormal placentation (6 decks)

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