Placenta Praevia and Placenta Accreta: Diagnosis and Management (Green-top Guideline No. 27a)

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Post category

Corresponding Author

the Royal College of Obstetricians, Gynaecologists

Publish date

09/27/2018
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Comment count

Executive summary

Antenatal diagnosis and care of women with placenta praevia or a low-lying placenta

What are the risk factors for women with placenta praevia or a low-lying placenta?

Caesarean delivery is associated with an increased risk of placenta praevia in subsequent pregnancies. This risk rises as the number of prior caesarean sections increases. [ New 2018 ]

Grade of recommendation: B

Assisted reproductive technology and maternal smoking increase the risk of placenta praevia. [ New 2018 ]

Grade of recommendation: B

Should we screen women for placenta praevia or a low-lying placenta, if so, at what gestation and with what follow-up?

The midpregnancy routine fetal anomaly scan should include placental localisation thereby identifying women at risk of persisting placenta praevia or a low-lying placenta. [ New 2018 ]

Grade of recommendation: ✓

The term placenta praevia should be used when the placenta lies directly over the internal os. For pregnancies at more than 16 weeks of gestation the term low-lying placenta should be used when the placental edge is less than 20 mm from the internal os on transabdominal or transvaginal scanning (TVS). [ New 2018 ]

Grade of recommendation: D

If the placenta is thought to be low lying (less than 20 mm from the internal os) or praevia (covering the os) at the routine fetal anomaly scan, a follow-up ultrasound examination including a TVS is recommended at 32 weeks of gestation to diagnose persistent low-lying placenta and/or placenta praevia.

Grade of recommendation: D

What is the role and what are the risks of TVS?

Clinicians should be aware that TVS for the diagnosis of placenta praevia or a low-lying placenta is superior to transabdominal and transperineal approaches, and is safe. [ New 2018 ]

Grade of recommendation: ✓

In women with a persistent low-lying placenta or placenta praevia at 32 weeks of gestation who remain asymptomatic, an additional TVS is recommended at around 36 weeks of gestation to inform discussion about mode of delivery. [ New 2018 ]

Grade of recommendation: D

Cervical length measurement may help facilitate management decisions in asymptomatic women with placenta praevia. A short cervical length on TVS before 34 weeks of gestation increases the risk of preterm emergency delivery and massive haemorrhage at caesarean section. [ New 2018 ]

Grade of recommendation: D

Where should women with a low-lying placenta or placenta praevia be cared for in the third trimester?

Women with recurrent bleeding (low-lying placenta or placenta praevia)

Tailor antenatal care, including hospitalisation, to individual woman’s needs and social circumstances, e.g. distance between home and hospital and availability of transportation, previous bleeding episodes, haematology laboratory results, and acceptance of receiving donor blood or blood products. [ New 2018 ]

Grade of recommendation: ✓

Where hospital admission has been decided, an assessment of risk factors for venous thromboembolism in pregnancy should be performed as outlined in the Royal College of Obstetricians and Gynaecologists Green-top Guideline No. 37a. This will need to balance the risk of developing a venous thromboembolism against the risk of bleeding from a placenta praevia or low lying placenta.

Grade of recommendation: D

It should be made clear to any woman being treated at home in the third trimester that she should attend the hospital immediately if she experiences any bleeding, including spotting, contractions or pain (including vague suprapubic period-like aches).

Grade of recommendation: ✓

Asymptomatic women (low-lying placenta or placenta praevia)

Women with asymptomatic placenta praevia or a low-lying placenta in the third trimester should be counselled about the risks of preterm delivery and obstetric haemorrhage, and their care should be tailored to their individual needs.

Grade of recommendation: ✓

Women with asymptomatic placenta praevia confirmed at the 32-week follow-up scan and managed at home should be encouraged to ensure they have safety precautions in place, including having someone available to help them as necessary and ready access to the hospital.

Grade of recommendation: ✓

Is there a place for cervical cerclage in women with placenta praevia or a low-lying placenta?

The use of cervical cerclage to reduce bleeding and prolong pregnancy is not supported by sufficient evidence to recommend its use outside of a clinical trial.

Grade of recommendation: ✓

In what circumstances, and at what gestation, should women be offered antenatal corticosteroids?

A single course of antenatal corticosteroid therapy is recommended between 34+0 and 35+6 weeks of gestation for pregnant women with a low-lying placenta or placenta praevia and is appropriate prior to 34+0 weeks of gestation in women at higher risk of preterm birth. [New 2018]

Grade of recommendation: ✓

Is there a place for the use of tocolytics in women presenting with symptomatic low-lying placenta or placenta praevia, who are in suspected preterm labour?

Tocolysis for women presenting with symptomatic placenta praevia or a low-lying placenta may be considered for 48 hours to facilitate administration of antenatal corticosteroids. [ New 2018 ]

Grade of recommendation: C

If delivery is indicated based on maternal or fetal concerns, tocolysis should not be used in an attempt to prolong gestation. [ New 2018 ]

Grade of recommendation: C

At what gestation should planned delivery occur?

Late preterm (34+0 to 36+6 weeks of gestation) delivery should be considered for women presenting with placenta praevia or a low-lying placenta and a history of vaginal bleeding or other associated risk factors for preterm delivery. [New 2018]

Grade of recommendation: C

Delivery timing should be tailored according to antenatal symptoms and, for women presenting with uncomplicated placenta praevia, delivery should be considered between 36+0 and 37+0 weeks of gestation. [New 2018]

Grade of recommendation: C

In what situations is vaginal delivery appropriate for women with a low-lying placenta?

In women with a third trimester asymptomatic low-lying placenta the mode of delivery should be based on the clinical background, the woman’s preferences, and supplemented by ultrasound findings, including the distance between the placental edge and the fetal head position relative to the leading edge of the placenta on TVS. [New 2018]

Grade of recommendation: D

Optimising the delivery of women with placenta praevia

Prior to delivery, all women with placenta praevia and their partners should have a discussion regarding delivery. Indications for blood transfusion and hysterectomy should be reviewed and any plans to decline blood or blood products should be discussed openly and documented.

Grade of recommendation: ✓

Placenta praevia and anterior low-lying placenta carry a higher risk of massive obstetric haemorrhage and hysterectomy. Delivery should be arranged in a maternity unit with on-site blood transfusion services and access to critical care.

Grade of recommendation: D

Women with atypical antibodies form a particularly high-risk group and the care of these women should involve discussions with the local haematologist and blood bank.

Grade of recommendation: D

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

Grade of recommendation: D

Delivery for women with placenta praevia or a low-lying placenta

What grade of obstetrician and anaesthetist should attend the caesarean delivery of a woman with placenta praevia?

As a minimum requirement for a planned caesarean section for a woman with placenta praevia, the surgical procedure should be carried out by an appropriately experienced operator. [ New 2018 ]

Grade of recommendation: ✓

In cases of planned caesarean section for placenta praevia or a low-lying placenta, a senior obstetrician (usually a consultant) and senior anaesthetist (usually a consultant) should be present within the delivery or theatre suite where the surgery is occurring.

Grade of recommendation: ✓

When an emergency arises, the senior obstetrician and senior anaesthetist should be alerted immediately and attend urgently.

Grade of recommendation: ✓

What anaesthetic procedure is most appropriate for women having a caesarean section for placenta praevia?

Regional anaesthesia is considered safe and is associated with lower risks of haemorrhage than general anaesthesia for caesarean delivery in women with placenta praevia or a low-lying placenta. Women with anterior placenta praevia or a low-lying placenta should be advised that it may be necessary to convert to general anaesthesia if required and asked to consent. [ New 2018 ]

Grade of recommendation: D

What blood products should be available?

Close liaison with the hospital transfusion laboratory is essential for women presenting with placenta praevia or a low-lying placenta. [ New 2018 ]

Grade of recommendation: ✓

Rapid infusion and fluid warming devices should be immediately available. [ New 2018 ]

Grade of recommendation: ✓

Cell salvage is recommended for women where the anticipated blood loss is great enough to induce anaemia, in particular, in women who would decline blood products.

Grade of recommendation: D

What surgical approach should be used for women with placenta praevia or a low-lying placenta?

Consider vertical skin and/or uterine incisions when the fetus is in a transverse lie to avoid the placenta, particularly below 28 weeks of gestation. [ New 2018 ]

Grade of recommendation: ✓

Consider using preoperative and/or intraoperative ultrasonography to precisely determine placental location and the optimal place for uterine incision. [ New 2018 ]

Grade of recommendation: D

If the placenta is transected during the uterine incision, immediately clamp the umbilical cord after fetal delivery to avoid excessive fetal blood loss. [ New 2018 ]

Grade of recommendation: D

If pharmacological measures fail to control haemorrhage, initiate intrauterine tamponade and/or surgical haemostatic techniques sooner rather than later. Interventional radiological techniques should also be urgently employed where possible. [ New 2018 ]

Grade of recommendation: C

Early recourse to hysterectomy is recommended if conservative medical and surgical interventions prove ineffective. [ New 2018 ]

Grade of recommendation: D

Antenatal diagnosis and outcome of women with placenta accreta spectrum

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. [ New 2018 ]

Grade of recommendation: B

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. [ New 2018 ]

Grade of recommendation: ✓

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. [ New 2018 ]

Grade of recommendation: D

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.

Grade of recommendation: D

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. [ New 2018 ]

Grade of recommendation: C

Refer women with any ultrasound features suggestive of placenta accreta spectrum to a specialist unit with imaging expertise. [ New 2018 ]

Grade of recommendation: B

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. [ New 2018 ]

Grade of recommendation: D

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. [ New 2018 ]

Grade of recommendation: C

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.

Grade of recommendation: ✓

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. [ New 2018 ]

Grade of recommendation: ✓

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. [ New 2018 ]

Grade of recommendation: D

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. [New 2018]

Grade of recommendation: ✓

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 haemorrhage. [ New 2018 ]

Grade of recommendation: ✓

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 haemorrhage, increased risk of lower urinary tract damage, the need for blood transfusion and the risk of hysterectomy.

Grade of recommendation: ✓

Additional possible interventions in the case of massive haemorrhage should also be discussed, including cell salvage and interventional radiology where available. [ New 2018 ]

Grade of recommendation: D

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 anaesthetists, obstetricians and gynaecologists with appropriate experience in managing the condition and other surgical specialties if indicated. In an emergency, the most senior clinicians available should be involved.

Grade of recommendation: ✓

What anaesthetic is most appropriate for delivery?

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

Grade of recommendation: ✓

The woman should be informed that the surgical procedure can be performed safely with regional anaesthesia but should be advised that it may be necessary to convert to general anaesthesia if required and asked to consent to this. [ New 2018 ]

Grade of recommendation: D

Optimising the delivery of women with placenta accreta spectrum

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

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

Grade of recommendation: C

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. [ New 2018 ]

Grade of 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. [ New 2018 ]

Grade of recommendation: D

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 (see section 8.4.2). [ New 2018 ]

Grade of recommendation: C

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. [ New 2018 ]

Grade of recommendation: D

Expectant management (leaving the placenta in situ)

Elective peripartum hysterectomy may be unacceptable to women desiring uterine preservation or considered inappropriate by the surgical team. In such cases, leaving the placenta in situ should be considered. [ New 2018 ]

Grade of recommendation: D

When the placenta is left in situ, local arrangements need to be made to ensure regular review, ultrasound examination and access to emergency care should the woman experience complications, such as bleeding or infection. [ New 2018 ]

Grade of recommendation: D

Methotrexate adjuvant therapy should not be used for expectant management as it is of unproven benefit and has significant adverse effects. [ New 2018 ]

Grade of recommendation: C

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. [ New 2018 ]

Grade of recommendation: D

Women diagnosed with placenta accreta spectrum who decline donor blood transfusion should be cared for in a unit with an interventional radiology service.

Grade of recommendation: D

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. [ New 2018 ]

Grade of recommendation: ✓

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. [ New 2018 ]

Grade of recommendation: D

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