Max Brinsmead MB BS PhD May 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 21 st 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 3 rd 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 w 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 w?  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

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