Placenta Accreta Spectrum (PAS): Diagnosis and Management

Recommendation

Strength

What are the risk factors for women with placenta accreta spectrum?

The major risk factors for placenta accreta spectrum are history of accreta in a previous pregnancy, previous caesarean delivery and other uterine surgery, including repeated endometrial curettage. This risk rises as the number of prior caesarean sections increases.

Strong Recommendation

Women requesting elective caesarean delivery for non-medical indications should be informed of the risk of placenta accreta spectrum and its consequences for subsequent pregnancies.

GPS

How can placenta accreta spectrum be suspected and diagnosed antenatally?

Antenatal diagnosis of placenta accreta spectrum is crucial in planning its management and has been shown to reduce maternal morbidity and mortality.

Strong Recommendation

Ultrasound assessment of placental location should be part of routine obstetric care, particularly in women undergoing cesarean section delivery.

GPS

Previous caesarean delivery and the presence of an anterior low-lying placenta or placenta praevia should alert the antenatal care team of the higher risk of placenta accreta spectrum.

Strong Recommendation

Ultrasound screening and diagnosis of placenta accreta spectrum

Ultrasound imaging is highly accurate when performed by a skilled operator with experience in diagnosing placenta accreta spectrum.

Strong Recommendation

Refer women with any ultrasound features suggestive of placenta accreta spectrum to a specialist unit with imaging expertise.

Strong Recommendation

Standardised definitions should be used in reporting and consideration given to using a template.

GPS

Women with a history of previous caesarean section seen to have an anterior low-lying placenta or placenta praevia at the routine fetal anomaly scan should be specifically screened for placenta accreta spectrum.

Strong Recommendation

Patients with previous one or more CS and diagnosed as CS scar pregnancy at 5-6 weeks of gestation are at high risk of developing placenta accreta. They should be counseled and referred to a tertiary hospital for termination of pregnancy.

Strong Recommendation

Is there a role for magnetic resonance imaging (MRI) in the diagnosis of placenta accreta spectrum?

Clinicians should be aware that the diagnostic value of MRI and ultrasound imaging in detecting placenta accreta spectrum is similar when performed by experts. 

Strong Recommendation

MRI may be used to complement ultrasound imaging to assess the depth of invasion and lateral extension of myometrial invasion, especially with posterior placentation and/or in women with ultrasound signs suggesting parametrial invasion.

GPS

Women with a history of previous cesarean delivery or uterine surgery who are found to have an anterior low-lying placenta or placenta previa should be considered at increased risk for placenta accreta spectrum, even if imaging does not confirm the diagnosis.

GPS

Where should women with placenta accreta spectrum be cared for?

Women diagnosed with placenta accreta spectrum should be cared for by a multidisciplinary team in a specialist centre with expertise in diagnosing and managing invasive placentation.

GPS

Prevention and treatment of anemia during the antenatal period is recommended for women with placenta praevia, a low-lying placenta or accreta as for any pregnant woman.

GPS

Delivery for women diagnosed with placenta accreta spectrum should take place in a specialist centre with logistic support for immediate access to blood products, adult intensive care unit and neonatal intensive care unit by a multidisciplinary team with expertise in complex pelvic surgery.

Strong Recommendation

When should delivery be planned for women with placenta accreta spectrum?

In the absence of risk factors for preterm delivery in women with placenta accreta spectrum, planned delivery at 35⁺⁰ to 36⁺⁶ weeks of gestation provides the best balance between fetal maturity and the risk of unscheduled delivery.

GPS

Planning delivery of women with suspected placenta accreta spectrum

Once the diagnosis of placenta accreta spectrum is made, a contingency plan for emergency delivery should be developed in partnership with the woman, including the use of an institutional protocol for the management of maternal hemorrhage.                        

GPS

What should be included in the consent form for caesarean section in women with suspected placenta accreta spectrum?

Any woman giving consent for caesarean section should understand the risks associated with caesarean section in general, and the specific risks of placenta accreta spectrum in terms of massive obstetric hemorrhage, increased risk of lower urinary tract damage, the need for blood transfusion and the risk of hysterectomy.

Strong recommendation

Additional possible interventions in the case of massive hemorrhage should also be discussed, including cell salvage and interventional radiology where available.

Conditional recommendation

What healthcare professionals should be involved?

The elective delivery of women with placenta accreta spectrum should be managed by a multidisciplinary team, which should include senior anesthetists, obstetricians and gynecologists with appropriate experience in managing the condition and other surgical specialties if indicated. In an emergency, the most senior clinicians available should be involved.

Strong Recommendation

What anesthetic is most appropriate for delivery?

The choice of anesthetic technique for caesarean section for women with placenta accreta spectrum should be made by the anesthetist conducting the procedure in consultation with the woman prior to surgery.

GPS

The woman should be informed that the surgical procedure can be performed safely with regional anesthesia but should be advised that it may be necessary to convert to general anesthesia if required and asked to consent to this.

GPS

What surgical approach should be used for women with placenta accreta spectrum?

Intravenous tranexamic acid should be administered at the commencement of surgery because it reduces intraoperative blood loss.

Strong recommendation

Caesarean section hysterectomy with the placenta left in situ is preferable to attempting to separate it from the uterine wall.

Strong recommendation

When the extent of the placenta accreta is limited in depth and surface area, and the entire placental implantation area is accessible and visualised (i.e., completely anterior, fundal or posterior without deep pelvic invasion), uterus preserving surgery may be appropriate, including partial myometrial resection.

Conditional recommendation

Uterus preserving surgical techniques should only be attempted by surgeons working in teams with appropriate expertise to manage such cases and after appropriate counselling regarding risks and with informed consent.

Conditional recommendation

There are currently insufficient data to recommend the routine use of ureteric stents in placenta accreta spectrum. The use of stents may have a role when the urinary bladder is invaded by placental tissue.

GPS

What surgical approach should be used for women with placenta percreta?

There is limited evidence to support uterus preserving surgery in placenta percreta and women should be informed of the high risk of peripartum and secondary complications, including the need for secondary hysterectomy.

GPS

When is interventional radiology indicated?

Larger studies are necessary to determine the safety and efficacy of interventional radiology before this technique can be advised in the routine management of placenta accreta spectrum. 

Strong recommendation

How are women with undiagnosed or unsuspected placenta accreta spectrum best managed at delivery?

If at the time of an elective repeat caesarean section, where both mother and baby are stable, it is immediately apparent that placenta percreta is present on opening the abdomen, the caesarean section should be delayed until the appropriate staff and resources have been assembled and adequate blood products are available. This may involve closure of the maternal abdomen and urgent transfer to a specialist unit for delivery. 

GPS

In case of unsuspected placenta accreta spectrum diagnosed after the birth of the baby, the placenta should be left in situ and an emergency hysterectomy performed. 

GPS