Placenta Praevia, Placenta Praevia Accreta and Vasa Praevia: Diagnosis and Management

Question 1

Can we diagnose placenta praevia clinically?

Answer 1

• Clinical suspicion should be raised in all women with vaginal bleeding after 20 weeks of gestation.
• A high presenting part, an abnormal lie and painless or provoked bleeding, irrespective of previous imaging results, are more suggestive of a low-lying placenta but may not be present, & definitive diagnosis usually relies on ultrasound imaging.

Question 2

Should we screen for placental localisation?

Answer 2

Routine ultrasound scanning at 20 weeks of gestation should include placental localisation.

Question 3

How should we image for placental localisation?

Answer 3

Transvaginal scans improve accuracy of placental localisation & safe, so suspected diagnosis of placenta praevia at 20 weeks of gestation by abdominal scan should be confirmed by transvaginal scan.

Question 4

Which women need further imaging if the placenta is low at 20 weeks of gestation?

Answer 4

• All women require follow-up imaging if placenta covers or overlaps cervical os at 20 wks gestation.
• Women with a previous CS require higher index of suspicion as two problems
  1- to exclude: placenta praevia and placenta accreta.
  2- If placenta lies anteriorly and reaches cervical os at 20 weeks, follow-up scan can help identify if it is implanted into CS scar.

Question 5

When should further imaging occur?

Answer 5

• Women who bleed should be managed individually according to their needs.
• asymptomatic women with suspected minor praevia, follow-up imaging can be left until 36 wks gestation.
• asymptomatic suspected major p. praevia or question of p.. accrete, imaging should be performed at around 32 weeks of gestation to clarify diagnosis and allow
  planning for third-trimester management, further imaging and delivery.

Question 6

How can a morbidly adherent placenta be diagnosed?

Answer 6

• previous CS who also have either p. praevia or an anterior placenta underlying old CS scar at 32 weeks of gestation are at increased risk of placenta accreta and should be managed as if they have placenta accreta, with appropriate preparations for surgery made.
• Antenatal sonographic imaging can be complemented by MRI in equivocal cases to distinguish those women at special risk of placenta accreta.

Question 7

Antenatal management of placenta previa

Answer 7

Prevention and treatment of anaemia during antenatal

Question 8

Where should placenta praevia be cared for in late third trimester?

Answer 8

Counselled risks of care tailored to individual needs.
1 - preterm delivery and
2 - obstetric haemorrhage,

Any home-based care:
1 - close proximity to hospital,
2- constant presence of a companion and
3 - full informed consent

Question 9

Where possible, home-based care should be conducted within a research context.

Answer 9

• ensure safety precautions in place, ( having someone available to help and, particularly, having ready access to hospital)
• attend immediately ifs any bleeding, contractions or pain (including vague suprapubic period-like aches).
• Decisions regarding blood availability during inpatient based on clinical factors relating to individual cases as well as on local blood bank services.
• atypical antibodies (high-risk group) discussions involve local haematologist and blood bank.

Question 10

Is there a place for cervical cerclage in these women?

Answer 10

Not sufficient evidence only clinical trial for following
1 - to reduce bleeding and
2- prolong pregnancy

Question 11

Is there a place for tocolytics in women who bleed?

Answer 11

For treatment of bleeding due to placenta praevia
in selected cases.
- beta-mimetics used in studies to date and, significant
adverse effects, agent and optimum regime are still to be determined: further research

Question 12

Is there a place for the use of prophylactic tocolytics in women to prevent bleeding?

Answer 12

Prophylactic terbutaline to prevent bleeding has not been found to benefit women with placenta praevia.

Question 13

What precautions should be taken against venous thromboembolism for inpatients?

Answer 13

• Prolonged inpatient care: increased risk of thromboembolism; mobility + TED thromboembolic deterrent stockings and adequate hydration.
• Prophylactic anticoagulation at high risk of bleeding can be hazardous and the decision to use on individual basis considering risk factors for thromboembolism.
• Limiting anticoagulant thromboprophylaxis to high risk of thromboembolism seems reasonable.

Question 14

Preparations for delivery

Answer 14

• Prior to delivery, all women with p. praevia and their partners should have discussion regarding delivery, indications for blood transfusion and hysterectomy should be reviewed, and any concerns, queries or refusals of treatment should be dealt with effectively and documented clearly.

Question 15

In what situations can vaginal delivery be contemplated for women with a low-lying placenta?

Answer 15

• mode of delivery should be based on clinical judgement supplemented by sonographic information.
• placental edge < 2 cm from internal os in 3rd trimtester is likely to need delivery by CS, especially if placenta is thick, but evidenc poor and further research needed.
• As lower uterine segment continues to develop beyond 36 weeks of gestation, place for TVS if fetal head is engaged prior to an otherwise planned CS.

Question 16

At what gestation should elective delivery occur?

Answer 16

Elective CS in asymptomatic women not recommended < 38 wks of gestation for p. praevia, or < 36–37 wks of gestation for suspected placenta accreta.

Question 17

What preparations should be made before surgery?

Answer 17

• Placenta praevia without previous CS carries risk of massive obstetric haemorrhage and hysterectomy and should be carried out in a unit with a blood bank and facilities for high dependency care.
• care bundle for suspected placenta accreta should be applied in all cases where there is a p. praevia and previous CS or anterior placenta underlying old CS scar.

Question 18

What blood products are needed?

Placenta praevia

Answer 18

• Blood should be readily available for peripartum period; whether ready cross-matched blood is required and in what amount will depend on the clinical features of each individual case and the local blood bank services available.
• When women have atypical antibodies, direct communication with local blood bank should enable specific plans to be made to match individual circumstance.

Question 19

Placenta praevia: autologous blood transfusion & Cell salvage

Answer 19

• no evidence to support use of autologous blood transfusion for placenta praevia.
• Cell salvage may be considered in women at high risk of massive haemorrhage and especially in women who would refuse donor blood.

Question 20

Suspected placenta accreta

Answer 20

Cross-matched blood and blood products should be readily available in anticipation of massive haemorrhage. Where available, cell salvage should be considered and if the woman refuses donor blood it is recommended that she be transferred to a unit with a cell saver.

Question 21

When is interventional radiology indicated?

Answer 21

• Interventional radiology can be life saving for treatment of massive PPH, & this facility available locally desirable.
• If woman is suspected of having p. accreta & she refuses donor blood, recommended to transferred to unit with interventional radiology service.
• place of prophylactic catheter placement for balloon occlusion or in readiness for embolisation if bleeding ensues requires further evaluation.

Question 22

What anaesthetic is most appropriate for delivery of the baby?

Answer 22

The choice of anaesthetic technique for caesarean sections for placenta praevia and suspected placenta
accreta must be made by the anaesthetist conducting the procedure. There is insufficient evidence to
support one technique over another.

Question 23

What should be included in the consent form for caesarean section?

Answer 23

Risks with CS in general and specific risks of placenta praevia in terms of massive obstetric haemorrhage, need for blood transfusion and chance of hysterectomy

Suspected praevia accreta by consultant in antenatal. risks and treatment options discussed and plan agreed, reflected clearly in consent form.
1- anticipated skin and
2-uterine incisions and
3- conservative MX or straight to hysterectomy where accreta is confirmed at surgery.
4- Additional possible interventions in case of massive haemorrhage (cell salvage & interventional radiology when available.)

Question 24

What grade of obstetrician should attend?

Answer 24

• junior doctor not unsupervised
• senior experienced obstetrician scrubbed in theatre.
• As minimum requirement during planned procedure for p. praevia, consultant obstetrician & anaesthetist should be present within delivery suite. When emergency arises, consultant staff alerted & attend ASAP.

suspected placenta praevia accreta

• going to theatre electively: attended by consultant obstetrician and anaesthetist.
• If delivery unexpected, out-of-hours consultant staff alerted & attend ASAP.

Question 25

What surgical approach should be used for suspected placenta praevia accreta?

Answer 25

• consider opening uterus at a site distant from placenta, and delivering baby without disturbing placenta, in order to enable conservative MX of placenta or elective hysterectomy to be performed if accreta is confirmed.
• Going straight through the placenta to achieve
  delivery is associated with more bleeding and a high chance of hysterectomy and should be avoided.
• Conservative management of placenta accreta when woman is already bleeding is unlikely to be successful and risks wasting valuable time.

Question 26

What should be done if the placenta does not separate after delivery of the baby?

Answer 26

If the placenta fails to separate with usual measures, leaving it in place and closing, or leaving it in place, closing the uterus and proceeding to a hysterectomy are both associated with less blood loss than trying to separate it.

Question 27

What happens if the placenta separates, or partially separates?

Answer 27

If the placenta separates, it needs to be delivered and any haemorrhage that occurs needs to be dealt
with in normal way.

If the placenta partially separates, separated portion(s) need to be delivered & any haemorrhage needs to be dealt normal way. Adherent portions can be left in place, but blood loss in such circumstances can be large and massive haemorrhage management needs to follow in timely fashion.

Question 28

How is massive haemorrhage best managed?

Answer 28

• surgical manoeuvres required in face of massive haemorrhage associated with placenta praevia CS should be performed by appropriately experienced surgeons.
• Calling for extra help early should be encouraged and not seen as ‘losing face’.

Question 29

How should the woman be managed after placental retention?

Answer 29

• warn: risks of bleeding and infection postoperatively and prophylactic antibiotics may be helpful in immediate postpartum period to reduce this risk.
• Neither methotrexate nor arterial embolisation reduces these risks and neither is recommended routinely.
• Follow-up of woman using ultrasound should supplement serum bHCG measurements.

Question 30

What chance of success can be quoted for a future pregnancy?

Answer 30

• insufficient data at present to make any firm prognosis about future pregnancy.

Question 31

Can we diagnose vasa praevia clinically?

Answer 31

• antenatally, in absence of vaginal bleeding, no method to diagnose vasa praevia clinically.
• In intrapartum period, in absence of vaginal bleeding, vasa praevia can occasionally be diagnosed clinically by palpation of fetal vessels in membranes at the time of vaginal examination.
• This can be confirmed by direct visualisation using an amnioscope.
• In presence of vaginal bleeding, especially associated with membrane rupture and fetal compromise, delivery should not be delayed to try & diagnose vasa praevia.

Question 32

Can we differentiate between fetal and maternal bleeding?

Answer 32

Various tests exist that can differentiate between fetal & maternal blood, but they often not applicable in clinical situation.

Question 33

Can vasa praevia be diagnosed using ultrasound?

Answer 33

Vasa praevia can be accurately diagnosed with colour Doppler ultrasound, often utilising the transvaginal
route.

Question 34

Should we screen for vasa praevia?

Answer 34

At present, vasa praevia should not be screened for routinely at the time of mid-trimester anomaly scan, as it does not fulfil criteria for screening programme.

Question 35

How should vasa praevia be managed?

Answer 35

• bleeding vasa praevia, delivery should be achieved by category 1 em CS.
• suspected vasa praevia, transvaginal colour Doppler ultrasonography to confirm the diagnosis.
• confirmed cases of vasa praevia at term, delivery by elective CS in timely manner.
• vasa p. identified in 2nd trimester, imaging repeated in 3rd trimester to confirm persistence.
• confirmed vasa praevia in third trimester, antenatal admission from 28 to 32 weeks, to unit with appropriate neonatal facilities will facilitate quicker intervention in the event of bleeding or labour.
• risk of preterm delivery, consider corticosteroids..
• confirmed vasa p., elective CS prior to labour onset.
• Laser ablation in utero may have a role in the treatment of vasa praevia.

Question 36

The six

elements considered to be reflective of good care were:

Answer 36

● consultant obstetrician planned and directly supervising delivery
● consultant anaesthetist planned and directly supervising anaesthetic at delivery
● blood and blood products available
● multidisciplinary involvement in pre-op planning
● discussion & consent includes possible interventions (such as hysterectomy, leaving the placenta in place,
cell salvage and intervention radiology)
● local availability of a level 2 critical care bed.

Question 37

The main MRI features of placenta accreta include:74

Answer 37

● uterine bulging
● heterogeneous signal intensity within the placenta
● dark intraplacental bands on T2-weighted imaging.

Question 38

Ultrasound criteria for diagnosis were as follows:

Greyscale:

Answer 38

● loss of the retroplacental sonolucent zone
● irregular retroplacental sonolucent zone
● thinning or disruption of the hyperechoic serosa–bladder interface
● presence of focal exophytic masses invading the urinary bladder
● abnormal placental lacunae.

Question 39

Ultrasound criteria for diagnosis were as follows:

Colour Doppler:

Answer 39

● diffuse or focal lacunar flow
● vascular lakes with turbulent flow (peak systolic velocity over 15 cm/s)
● hypervascularity of serosa–bladder interface
● markedly dilated vessels over peripheral subplacental zone.

Question 40

Ultrasound criteria for diagnosis were as follows:

Three-dimensional power Doppler:

Answer 40

● numerous coherent vessels involving whole uterine serosa–bladder junction (basal view)
● hypervascularity (lateral view)
● inseparable cotyledonal and intervillous circulations, chaotic branching, detour vessels (lateral view).