Placenta Praevia and Placenta Accreta

Placenta praevia is defined as placenta lies directly over the internal os
Low lying placenta: placental edge less than 20 mm from internal os on transabdominal or transvaginal scan after 16 weeks

Risk Factors

Caesarean delivery
Maternal smoking
Assisted reproductive technology
Rising maternal age
Short interpregnancy interval after caesarean section
Prelabour caesarean section

Antenatal screening

Mid-pregnancy routine fetal anomaly scan 18+6 -21+6 weeks gestation
Placental localization during anomaly scanning
Identify women at risk of persisting placenta praevia or low-lying placenta
Organise follow up scan at 32 weeks for women with either low lying placenta/Placenta praevia
Transvaginal scan is safe and superior to transabdominal scan
Asymptomatic women with persistent placenta praevia or low-lying placenta should have a follow up scan at 36 weeks
Short Cervical length at gestational age below 34 weeks increases risk of preterm emergency delivery and massive haemorrhage at caesarean section
The use of cervical cerclage to reduce bleeding and prolong pregnancy is not supported by sufficient evidence
Prevent and treat anaemia in all pregnant women

Management of Women with recurrent bleeding

Tailor hospitalization with individual needs and social circumstances e.g. Distance of home to hospital, Transportation, Previous bleeding episodes
Check haematology laboratory results
Discuss acceptance of donor blood or blood products
Do Risk assessment for VTE and balance against risk of bleeding

Women managed at home should attend hospital immediately;

If bleeding or Spotting
Contractions
Vague suprapubic pain

Antenatal steroids

Administer single course of steroids at 34-35+6 weeks
Before 34 weeks; if high risk for preterm delivery
Tocolysis may be considered for 48 hours to administer steroids
If delivery is indicated e.g. active bleeding, fetal or maternal compromise, tocolysis should not be used

Planned Delivery

Uncomplicated placenta praevia: delivery 36-37 weeks
Vaginal bleeding and risk for preterm delivery: 34-36+6 weeks

Is Vaginal delivery appropriate for women with a low-lying placenta?

When placenta edge is between 10-20mm from the internal os success rates of vaginal delivery varies widely from 56%-93% (From small retrospective and observational studies)

In women with a third trimester asymptomatic low- lying placenta the mode of delivery should be based on

Maternal preference
Thickness of placental edge
Position of head in relation to lower edge of placenta

Optimising delivery

Discussion about blood transfusion and hysterectomy
Placenta praevia and anterior low-lying placenta carry high risk of Massive Obstetric Haemorrhage therefore delivery should be in a maternity with on-site blood transfusion services, Access to critical care
Women with atypical antibodies: discuss with blood bank and haematologist

Delivery

Should be performed by appropriately experienced operator
Senior Obstetrician (Usually Consultant) and senior anaesthetist usually consultant must be present in theatre suite
Consultants obstetrician and anaesthetist should be Alerted immediately and attend urgently when an emergency arises
Regional anaesthesia is appropriate and safe
Consent patient for conversion to GA if required

Blood products

Close liaison with the hospital transfusion laboratory
Cell salvage
Rapid infusion and fluid warming devices should be immediately available

Surgical approach in managing Placenta praevia

Vertical incision: transverse lie and less than 28 weeks
Ultrasound to determine optimal place for uterine incision
If placenta transected, immediately clamp umbilical cord to minimize blood loss
Pharmacological measures-syntocinon, syntometrine, carbaprost, misoprostol
intrauterine tamponade e.g. Bakri Balloon
Surgical haemostatic techniques e.g. B-Lynch brace sutures, uterine artery ligation, internal iliac ligation
Early recourse to hysterectomy

Placenta Accreta spectrum

Risk factors for Placenta Accreta

History of accreta in previous pregnancy
History of caesarean delivery
No. of previous caesareans
History of prelabour caesarean section: 3 times more likely (Kamara et al 2013)
Other uterine surgery
Repeated uterine curettage
Previous caesarean and anterior low lying or placenta praevia
Risk rises as the number of prior caesarean sections increases

Antenatal Diagnosis of placenta accrete spectrum

Ultrasound is highly accurate when performed by a skilled operator-Uterus bladder interface, abnormal vasculature, placental lacunae, moth eaten appearance and increased vascularity of placental bed
MRI scan (also used to compliment ultrasound) shows the depth of invasion and lateral extension of myometrial invasion Abnormal uterine bulge, dark intraplacental bands on T2-weighted imaging, heterogeneous signal intensity within the placenta, disorganised vasculature of placenta and disruption of the uteroplacental zone

Complications

Hamorrhage and hysterectomy
Placenta percreta: uterine rupture and bladder involvement

Delivery of placenta accrete

If there is no risk factors for preterm delivery deliver between 35-36+6 weeks
Make contingency plan with woman
Discuss Institutional protocol for massive haemorrhage with woman
Take Consent and discuss massive obstetric haemorrhage, increased risk of lower urinary tract damage, the need for blood transfusion and the risk of hysterectomy.
Discuss Cell salvage and Interventional radiology where available
Regional anaesthesia may require conversion to general anaesthesia
Caesarean hysterectomy is preferable when compared to attempt to separate placenta
Consider Uterus preserving surgery: partial myometrial resection if extent is limited
Placenta percreta hysterectomy
Placenta left in situ: bleeding and infection
Methotrexate not recommended
Ureteric stents if bladder involved

Care bundle

Consultant obstetrician planning and directly supervising delivery.
Consultant anaesthetist planning and directly supervising anaesthesia at delivery.
Blood and blood products availability.
Multidisciplinary involvement in preoperative planning.
Discussion and consent, including possible interventions (such as hysterectomy, leaving the placenta in salvage and interventional radiology).
Local availability of a level 2 critical care bed.

Surgical approach in placenta accreta

Primary hysterectomy without attempting placental separation
Delivery of the fetus avoiding the placenta, with repair of the incision leaving placenta in situ
Delivery of the fetus without disturbing the placenta, followed by partial excision of the uterine wall (placental implantation site) and repair of the uterus.
Delivery of the fetus without disturbing the placenta, and leaving it in situ, followed by elective secondary hysterectomy 3–7 days following the primary procedure.

Undiagnosed placenta accreta

Undiagnosed placenta percreta-Delay delivery if possible until resources available
You may need to close abdomen and transfer to specialist unit
Where appropriate leave placenta in situ after delivery
Emergency hysterectomy

Risk Management

Debriefing
Training
Incident reporting

Reference

Placenta Praevia and Placenta Accreta: Diagnosis and management-Green-top Guideline No. 27a September 2018