Max Brinsmead MB BS PhDMay 2015

RCOG Green-top Guideline number 27 January 2011

“Placenta praevia, placenta praevia accreta and vasa praevia: diagnosis and management”

Plus a few personal observations

In the 21st century placenta previa is best defined as an ultrasound observation of the placenta in the lower segment of the uterus Major = the placenta covers the internal os Minor (or Partial) = all the others

Problems: The lower segment does not develop until the

last trimester of pregnancy There is no agreed definition of where the

lower segment begins ultrasonically But the internal os is a fixed point that can be

identified with ultrasound So all minor degrees of previa should be

defined in relation to this

Placenta accreta occurs when the placental trophoblast has penetrated the decidua basalis▪ This is the plane of normal separation in the

3rd stage of labour▪ This definition incorporates p. increta and p.

percreta

Vasa previa exist when fetal blood vessels within membranes run across the cervical os and below the presenting part

Placenta previa 1:200 pregnancies

Placenta previa accreta No previous CS 3% One previous CS 11% Two previous CS 40% ≥3 previous CS >60%

Vasa previa 1:2000 – 1:6000 When fetal bleeding occurs then the

perinatal mortality is >60%

Clinical suspicion for all women with APH after 20w gestation especially with…

Painless bleeding A high presenting part Irrespective of previous US imaging

Screening for placenta previa occurs with the 18-22w morphology scan When a diagnosis of “low-lying placenta”

may be as high as 1:10

What should be done when the placenta is said to be “low lying” at the screening scan at 18 -20w?

First perform vaginal scan and…▪ 26-60% of LLP will be reclassified

Placental migration will occur in ≈90% LLP

But is less likely when…

▪ The placenta is posterior▪ Placenta is anterior and there has been a

previous CS▪ There is a major degree of previa

(>25 mm over the internal os)

Repeat the scan if there is a clinical need▪ Usually APH

Repeat the scan at 32w when…

▪ The placenta is anterior & there has been a previous CS

▪ Look for evidence of accreta▪ There is a major degree of previa (over the

internal os)

For women with minor PP and no symptoms it is best to defer the scan until 36w

Greyscale ultrasound has 95% sensitivity and 82% positive predictive value.

Look for… Loss of the retroplacental echolucent zone An irregular “ “

" Thinning or disruption of the hyperechoic

serosa/bladder zone Exophytic masses invading bladder Abnormal placental lacunae

Diagnosis can be enhanced using Colour Doppler 3-D Doppler MRI

Prevent and treat anaemia Individualize management when there

is APH or major PP. Home care is possible when…

Immediate transfer to hospital is possible An adult is with the woman at all times Informed and understanding patient Admission occurs if there is any bleeding,

pain or contractions

Tocolysis okay in the absence of severe APH

Group & Save according to local protocols

Beware of thromboembolism with prolonged immobilisation

This decision should be based on clinical judgement supplemented by ultrasound findings

If the placenta is >2 cm from the internal os (and not thick or posterior) then the vaginal delivery rate is >70% If the placenta is <2 cm from the internal os

then the vaginal delivery rate is 12.5%

There is still a role for EUA or amniotomy in theatre at 38+w for minor placenta previa The aim is to bring the head into the lower

segment and rupture the membranes

Patient Information Depends on the clinical scenario For major placenta previa…▪ Risk of major haemorrhage 1:5▪ Risk of hysterectomy 1:10▪ Return to theatre rate 75:1000▪ Bladder injury 23:1000

For previa and previous CS…▪ Risk of hysterectomy is 1:3

For placenta previa accreta…▪ Hysterectomy “very likely”

Consider Place of Delivery▪ ICU and facilities for management massive

haemorrhage Assemble and brief a multidisciplinary team

▪ Anaesthetist, Vascular surgeon, Interventional radiologist etc

▪ Role of prophylactic arterial catheter balloon uncertain

Aim for 38+ weeks for asymptomatic patients and those with minor previa

Use corticosteroids for lung maturation for deliveries that are mandated <38w

Aim for 36 – 37w for those with suspected placenta previa accreta

Consultant obstetrician & anaesthetist available for all Depends on the clinical scenario

Regional block anaesthesia not excluded Consider facilities for cell salvage and

transfusion▪ Especially when a mother refuses transfusion

Surgical tips▪ Use all available techniques for continuing

bleeding after removal of a placenta previa e.g. Oxytocics, direct suture, B-Lynch suture, ut. artery embolisation hysterectomy etc.

▪ Try to avoid section through a placenta accreta

▪ Do not attempt to remove a morbidly adherent placenta▪ Hysterectomy with placenta intact or ▪ Leave the placenta behind when uterine

conservation desired

Provide broad spectrum antibiotics

Methotrexate and or prophylactic arterial embolisation not recommended

Follow with ultrasound and beta-HCG

Risk of haemorrhage is 35%

Risk of infection is 18%

Risk of DIC is 7%

Bi-Lobed or Succinturiate placenta

Low lying placenta in the second trimester

Multiple pregnancy

IVF where the incidence may be as high as

1:300

Always consider this when a (dark) APH occurs Especially if it occurs at the time of spontaneous

or artificial rupture of membranes Rapid test for fetal HB desirable

▪ The best uses 0.14M NaOH▪ But do not delay IMMEDIATE delivery if there is

a strong clinical suspicion or a deteriorating CTG

Diagnosis can sometimes be made by palpation and or amnioscopy

Screening for vasa previa is not recommended because it does not fulfil screening criteria▪ But it can be detected with ≈90% specificity

using colour Doppler ▪ Sensitivity uncertain

Please leave a note on the Welcome Page to this website