The role of interventional radiology in managing placenta accreta spectrum

Learning objectives.

By reading this article you should be able to:

• •Describe the vascular supply to the uterus.
• •Explain the pathophysiology of placenta accreta spectrum (PAS) and why the incidence will increase.
• •Outline the various interventional radiology (IR) techniques used in managing major haemorrhage associated with PAS.
• •Detail the challenges of caring for patients with PAS in IR or hybrid theatres.

Key points.

• •PAS is characterised by abnormal placentation.
• •The uterine blood supply in PAS may involve formation of extensive collateral vessels.
• •PAS can result in life-threatening haemorrhage and infertility.
• •Emerging strategies to manage PAS-associated haemorrhage include IR techniques (endovascular balloon placement and artery embolisation), and surgical ligation of arteries.
• •Evidence and experience of managing PAS should be shared within specialist PAS networks.

Placenta accreta spectrum (PAS) is a disease of abnormal placentation associated with life-threatening haemorrhage and unique anaesthetic and surgical challenges. Placenta accreta spectrum disorders have evolved into one of the major iatrogenic public health challenges of the 21st century. As the incidence of PAS increases, so does the desire to find new ways to manage its consequences, to preserve life and fertility. In this review we describe the use of interventional radiology (IR) in managing the haemorrhage associated with PAS, including different IR techniques and their evidence base.

Vascular supply of the uterus

The uterus is situated in the pelvis, lying between the bladder and rectum. In its non-gravid state, the uterus measures around 7.5 × 5.0 × 2.5 cm and requires a blood flow of 50–100 ml min⁻¹. During pregnancy the uterus undergoes vast structural and cellular changes to accommodate the developing fetus requiring up to 700 ml min⁻¹ or 10% of total cardiac output.^1,2

At term, about 80% of uterine blood flow perfuses the intervillous spaces within the placenta, while the other 20% supports the myometrium. Autoregulation of uterine blood flow is minimal, as the uterine vessels are fully dilated throughout pregnancy. Therefore, maternal cardiac output, uterine vascular resistance and uterine perfusion pressure dictate uterine and placental blood flow.

Normal vascular supply to the uterus is from three main arteries:

• (i)the uterine arteries from the anterior division of the internal iliac arteries;
• (ii)the vaginal arteries, also from the anterior division of the internal iliac artery;
• (iii)the ovarian arteries, which are direct branches of the aorta.

• The ovarian artery contributes to around 35% of the uterine blood flow and is therefore important to block when IR is chosen to arrest haemorrhage. Nearly 12% of haemorrhage events in PAS originate from the ovarian artery.³

Further collateral blood supply can arise from the lumbar, median sacral, inferior mesenteric, iliolumbar arteries and external iliac artery anastamoses.^4,5

The presence of extensive collateral arterial supply to the uterus in patients with PAS may explain why there have been reports of limited success with some of the devascularisation techniques.⁶

Pathophysiology

In pregnancy, placental villi normally invade into the decidual layer of the uterus enabling uncomplicated separation of the placenta from the uterus at birth. In PAS these villi can penetrate through the myometrium and uterine serosa to invade local structures including the bladder and pelvis. In these cases, placental separation is incredibly challenging and can result in major haemorrhage with PAS as the leading cause of peripartum hysterectomy worldwide.⁷

Management strategies for PAS remain diverse, and literature interpretation is complicated by a range of terminology. The International Federation for Gynaecology and Obstetrics (FIGO) published guidance in 2018 to improve PAS diagnosis and management by standardising definitions (Box 1).

Box 1. FIGO (International Federation for Gynaecology and Obstetrics) classification for placenta accreta spectrum.8.

Grade 1—Abnormally adherent placenta (placenta accreta) when the villi adhere directly to the myometrium without a decidual interface.

Grade 2—Abnormally invasive placentation (placenta increta) when the villi invade into the myometrium.

Grade 3—Abnormally invasive placentation (placenta percreta) when the villi invade the full thickness of the uterine wall either to the serosa or beyond. They are subdivided into: Grade 3a, limited to and including the uterine serosa; Grade 3b, when there is urinary bladder invasion; Grade 3c, when there is invasion of other pelvic tissue/organs.

Alt-text: Box 1

The greater the severity of PAS the higher the maternal morbidity associated with it and the greater risk of haemorrhage-related mortality.⁹ Risk factors for PAS include surgery involving the endometrium (e.g. Caesarean section [CS]) and repeated endometrial curettage, current placenta praevia with history of CS, in vitro fertilisation, parity ≥2 and maternal age of ≥35 yrs.^10,11 A previous history of uterine artery embolisation is also a risk factor for PAS.¹²

The incidence of PAS in the UK is low estimated at 1.7 per 10,000 maternities.¹⁰ However, this is set to increase because of the increase in CS rates worldwide. The current global CS rate is 21% and is projected to increase to 30% (38 million) by the year 2030.¹³ Caesarean section is thought to increase the risk of PAS when abnormal decidualisation over the area of scarred tissue from the previous uterine incision occurs. This can result in abnormally deep invasion of the placental villi¹⁴ (Table 1).

Table 1.

Comparison of the percentage risk of placenta accreta spectrum with number of previous Caesarean deliveries without and with placenta praevia.¹⁵

Number of previous Caesarean deliveries	0	1	2	3	4	≥5
Percentage risk of PAS (no praevia)	0.03	0.2	0.1	0.8	0.8	4.7
Percentage risk of PAS with praevia	3	11	40	61	67	67

Early identification is essential to achieve the best outcomes. Antenatal diagnosis is confirmed by ultrasound and sometimes MRI. The patients should then be referred to specialist centres who have a complete PAS multidisciplinary team (MDT).¹⁶

Delivery usually occurs between 34 and 36 weeks of gestation, depending on the severity of the condition. At least 1 week before delivery, each case will be discussed during a planning meeting with the full PAS MDT. During this meeting the grade of PAS will be confirmed and risk of major haemorrhage stratified. The mode of delivery and therefore anaesthesia will be determined and the location of the delivery and the need for specialist interventions such as urology, radiology and haematology. The patients are then seen in clinic in advance of surgery and the care plan discussed with them in full.

There are many ways in which obstetric blood loss can be mitigated during Caesarean delivery including vessel clamping, ligation, embolisation and balloon occlusion.⁶

Options to decrease surgical blood loss during Caesarean hysterectomy include multivessel surgical ligation; temporary aortic clamping; multivessel embolisation; and balloon occlusion of the aorta or iliac arteries.³

Role of interventional radiology techniques

As the incidence of PAS increases, so too have the therapeutic options to manage associated major haemorrhage. Since the emergence in 1979 of endovascular balloon occlusion in managing haemorrhage, IR techniques continue to play an increasingly important role in the management of patients with PAS.^17,18

Interventional radiology techniques can reduce blood loss by acting as adjuncts to surgery, providing a clear surgical field that enables the surgeon to decide how best to achieve ultimate haemostasis. Interventional radiology techniques are also used as a strategy in their own right where balloon occlusion and artery embolisation are used to arrest major haemorrhage often in emergency settings, for example post-surgical rebleeding. Balloon-based IR techniques include prophylactic balloon occlusion of internal iliac arteries (PBOIIA) and prophylactic balloon occlusion of the abdominal aorta (PBOAA). Embolisation-based IR strategies include multivessel pelvic arterial embolisation. These are detailed below (Box 2).

Box 2. The ideal interventional radiology technique.

-Sustained cessation of uterine blood flow to enable a clear surgical field.

-Captures collateral vessels supplying the uterus.

-Preserves blood flow to vital organs (e.g. kidneys).

-Technically easy and quick to perform.

-Minimal radiation.

-Minimal adverse effects, and any should be reversible or of low severity.

-Preserves ovarian function.

Alt-text: Box 2

Evidence

Most of the literature for IR techniques in managing PAS originates from small, retrospective, single-centre studies. In addition, these studies are almost all non-randomised with a high potential for bias, and therefore it is very difficult to draw clear conclusions or recommendations for best practice. There is significant heterogeneity in endovascular techniques (grossly categorised into balloon occlusion or arterial embolisation), approaches to placental management, study methods and outcome measures and inclusion criteria spanning a wide range of PAS severity.

Prospective data are beginning to emerge for balloon occlusion techniques but there are minimal comparative data between targeted levels of the vascular system. Embolisation approaches have evolved in the past decade, thus the best quality data are retrospective, before and after protocol development.6, 19 Nevertheless, recent meta-analyses of both balloon occlusion and multivessel embolisation techniques show they can reduce haemorrhage and associated morbidity in appropriately selected cases of PAS.20, 21

A systematic review of 69 studies included 1811 patients, 77% of whom underwent endovascular procedures to control haemorrhage.⁶ This study also conducted a meta-analysis on the subset of included studies that addressed PBOAA (four studies, 441 patients) and prophylactic balloon occlusion of the internal iliac arteries (PBOIIA; seven studies, 360 patients). The review concluded that endovascular intervention reduced blood loss in PAS, and the meta-analysis results supported the conclusion that PBOAA was associated with the lowest blood loss, the lowest rate of maternal and fetal complications and the lowest doses of maternal and fetal radiation.⁶

While many previous studies reported weak results from uterine artery embolisation, the technique was generally used in its early years, as an adjunct to manage ongoing bleeding with arterial balloons already in use. Furthermore, early attempts at embolisation in the PAS focused on the uterine arteries alone, which is clearly insufficient to overcome the significant collateral neovascularisation from other large branches of the pelvic arteries. Several centres have since optimised targeted multivessel embolisation, which has the potential to overcome the dilemma of collateral circulation to clear the operative field.⁶,¹⁹,²²

Meta-analysis of embolisation data in PAS (16 studies, 805 patients) has demonstrated that arterial embolisation in PAS reduces intraoperative blood loss and need for hysterectomy.²¹

Prophylactic balloon occlusion of internal iliac arteries

Bilateral balloon occlusion of the internal iliac arteries minimises pelvic blood flow. In non-accreta cases, up to 90% of uterine blood flow comes from the anterior branch of the internal iliac artery.²³ This distribution may be different in patients with PAS who can develop extensive collateral blood supply which may limit the haemostatic effect of internal iliac balloon occlusion and is a management challenge in even the most experienced surgical hands (Table 2).

Table 2.

Evidence for prophylactic balloon occlusion of the internal iliac arteries (PBOIIA).

Advantages	Disadvantages	Evidence
•Reversible •Simple and fast to perform •May reduce overall blood loss and transfusion requirements •May reduce need for hysterectomy •Allows for sustained and intermittent occlusion of vessels	•Higher radiation dose compared with prophylactic balloon occlusion of the abdominal aorta (4.4 mGy) •Lower limb or buttock claudication •Arterial thrombosis	There is no clear conclusion in the use of prophylactic balloon occlusion of the internal iliac arteries with regards to the primary endpoint of reducing blood loss at CS with some studies demonstrating a statistically significant difference24, 25, 26, 27 and others failing to28, 29, 30, 31, 32

Anaesthesia for PBOIIA

In the author's institution, the entire procedure is performed with the patient awake (which limits fetal exposure to general anaesthetic agents) under a neuraxial block—combined spinal and epidural (CSE)—in ‘hybrid’ theatres where the CS takes place as part of the same procedure. The next most appropriate place to perform these would be in main operating theatres, ideally the largest theatre with space for the MDT and a ‘C-arm’ (a mobile imaging unit used for fluoroscopic imaging during surgery).

The epidural component of the CSE allows extension of the sensory block to accommodate every stage of the procedure including endovascular balloon insertion, CS with or without hysterectomy and postoperative embolisation, while keeping the patient awake. The need for a general anaesthetic in these patients is rare and has been used only in our unit because of allergy to local anaesthetic drugs. The patient's partner is present for the duration of the procedure.

Two large-bore venous cannulae (preferably 16G or larger) and one radial arterial catheter are inserted and monitoring applied as per the Association of Anaesthetists' guidelines. Full preparation is made for large blood loss including immediate access to cross-matched blood and blood products, a prophylactic i.v. dose of tranexamic acid 1 g and priming of the cell salvage machine and rapid infuser. Intravenous fluids are running, and a single dose of antibiotic is given at this stage. Emergency drugs are prepared, and an infusion of phenylephrine is started after the CSE has been sited.

We perform the CSE using hyperbaric bupivacaine and a long-acting opioid such as diamorphine or preservative-free morphine. The target of sensory blockade is to the level of the T4 dermatome bilaterally. Additional local anaesthetic is given via the epidural catheter about 60 min into the procedure.

The patient is actively warmed in the supine position with left uterine displacement. Fetal monitoring remains on throughout the anaesthetic preparation and endovascular balloon insertion. Within about 10 min of the CSE placement and if at least a T10 sensory block has been achieved, a urinary catheter is inserted, and balloon insertion begins, which takes 30–45 min. If ureteric stenting is indicated this would be performed before balloon insertion. At this point a ‘time out’ with the entire PAS team is undertaken and the CS begins.

Blood loss is meticulously monitored throughout the procedure and early declaration of major obstetric haemorrhage (MOH) is essential. Close communication between the MDT here is paramount to ensure seamless computation of the evolving clinical picture and timely use of the available anti-haemorrhage techniques.

The use of uterotonics should be guided by the obstetricians and are often avoided altogether as they can exacerbate blood loss through partial detachment of the placenta.

Patients should be recovered in a closely monitored setting, dependent on their clinical status—if stable, this could be in a level 2 care bed or in an ICU if mechanical ventilatory and high level haemodynamic support is required.

Pain relief is via the epidural with infusion of levobupivacaine 0.125% and fentanyl 1 μg ml⁻¹ running at 0–15 ml h⁻¹. The epidural catheter is removed after 24 h.

Interventional radiology for PBOIIA

Bilateral sheaths are inserted into the femoral arteries using ultrasound guidance and a Seldinger technique. The endovascular balloons are inserted through the sheath and their correct placement confirmed by a test inflation with normal or heparinised saline. An injection of dilute contrast is then administered which enables the correct position of the balloon to be confirmed and effective blockage of blood flow through the internal iliac artery (IIA). Once confirmed the balloons are deflated and the CS commences.

Immediately after the baby has been delivered and the umbilical cord clamped, the balloons are inflated for 5 min, followed by a 10-s deflation and a further 5-min inflation. This cycle is continued until the surgical team achieve haemostasis.

To finish, the IIAs and abnormal vessels identified on angiogram are routinely embolised with Gelfoam. This achieves a temporary blockage of about 7 days.

The sheaths are removed immediately after the procedure and manual compression applied to the puncture site for 15 min. The patient must lie supine for the next 2 h. Consider leaving one sheath in place for a further 24 h if the risk of rebleeding is particularly high but this should be decided per case. The rate of return and need for re-embolisation is very low. There is a theoretical concern about reperfusion injury, but this has not occurred in our experience.

Prophylactic balloon occlusion of abdominal aorta

Prophylactic balloon occlusion of abdominal aorta is performed using a resuscitative endovascular balloon occlusion of the aorta (REBOA) balloon, which is usually sited in zone 3 of the aorta, which extends from the lowest renal artery to the aortic bifurcation. Balloon deployment here achieves the best possible haemostasis while minimising the ischaemic insult to major abdominal viscera (Table 3). Minimal inflation times are preferred but the balloon can remain inflated for up to 60 min. Long inflation times increase the risk of ischaemia–reperfusion injury (IRI). Ischaemia–reperfusion injury should be anticipated and minimised by a coordinated slow deflation of the balloon alongside adequate intravascular filling, vasopressor use, correction of metabolic derangements and maintenance of normothermia.³³

Table 3.

Evidence for prophylactic balloon occlusion of the abdominal aorta (PBOAA).

Advantages	Disadvantages	Evidence
•Clear and dry surgical field—captures all collaterals •Reduces overall blood loss •Reduces hysterectomy rate •Decreased risk of complications in mother and fetus •Low radiation doses compared with prophylactic balloon occlusion of the internal iliac arteries	•Allows for intermittent occlusion only •Embolisation of the lower extremities •Ischaemic injury of the myocardium, kidneys, lungs, intestines, spinal cord •Rupture/dissection of the aorta •Increases arterial pressure	Initially evidence for balloon occlusion of the aorta came from trauma studies where noncompressible truncal haemorrhage has been successfully treated using this technique.34 The benefits of prophylactic balloon occlusion of the abdominal aorta in managing placenta accreta spectrum have been outlined earlier and include; reducing blood loss at Caesarean section, reducing the need for blood transfusion and reducing the risk of hysterectomy. These findings have been corroborated by several studies including two meta-analyses.20, 35, 36

A further consequence of this technique is the marked increase in arterial pressure during balloon inflation with potential to exacerbate preexisting cardiac, cerebral or pulmonary disease. The adoption of PBOAA for patients with PAS in the UK is not widespread, and the technique is still being developed.

Anaesthesia for PBOAA

In our institution, less severe cases of PAS are typically managed under neuraxial anaesthesia (CSE) with conversion to general anaesthesia if hysterectomy is indicated. The following anaesthetic management would be for moderate to severe cases.

Standard monitoring is applied and the first wide-bore i.v. cannula sited (preferably 16G or larger). A CSE or spinal is then performed with intrathecal dosing as described for PBOIIA. Full preparation for major blood loss is taken and, as before, includes ready availability of cross-matched blood and blood products (the amount prepared varies between institution and is decided during the antenatal PAS MDT planning phase), prophylactic tranexamic acid, cell salvage and rapid infusers are primed and ready. Emergency drugs are prepared at the discretion of the anaesthetist but should include peripheral and centrally acting vasopressors.

General anaesthesia is induced and the airway secured by video laryngoscopy and a cuffed tracheal tube. General anaesthesia is maintained with sevoflurane with bispectral index monitoring. The second wide-bore i.v. access is secured, a radial arterial and central venous catheters are inserted—one quadruple lumen central venous catheter and an MAC catheter (dual lumen 9-Fr and 12G catheters) usually in the right internal jugular vein. The patient is actively warmed and fetal monitoring is performed intermittently during this stage. ‘Time outs’ are performed for each stage of the procedure, for example, before cystoscopy and ureteric stenting, insertion of the REBOA and before starting the CS.

Blood loss is monitored very closely and again early declaration of MOH is key. Point of care clotting measurement can also assist blood product administration such as ROTEM. Rectus sheath catheters are inserted at the end of the procedure. After the procedure these patients are managed in a level 3 or level 2 facility. The choice rests on a combination of the amount of blood lost and comorbid state of the mother. Obstetric HDU (level 2) is preferable as it enables mother and baby to remain together. Large-bore cannula remain in place for 24 h after the procedure.

Interventional radiology for PBOAA

A single REBOA sheath (7-Fr gauge) is inserted in the right femoral artery using ultrasound guidance. The REBOA balloon is then inserted to zone 3, the depth of which is determined by preoperative MRI measurement. The line is transduced and a characteristic arterial waveform is seen. The balloon is inflated with 5 ml saline and adequate inflation indicated by a decrease in arterial pressure, and loss or change in the arterial waveform. Heparinised saline is used to flush the sheath to prevent thrombus formation. The balloon is usually inflated immediately after delivery of the baby and remains inflated until haemostasis is achieved. Deflation of the balloon is performed slowly under close consultation with the MDT to ensure adequate (but not excessive) intravascular filling and that vasopressor and metabolic support is ready. The sheath is removed at the end of the procedure and pressure applied to the puncture site for 15 min.

Embolisation-based IR strategies: multivessel pelvic arterial embolisation

Abnormal growth and location of placental tissue in PAS may result in severe distortion of the pelvic anatomy, including development of rich vascular anastomoses that can arise from any portion of the pelvic vasculature. Individual arteries supplying the uterus and aberrantly located placental tissue can be occluded systematically to dry the operative field and allow for a meticulous surgical approach to both reduce blood loss and minimise injury to surrounding pelvic structures (Table 4). There is a risk of ischaemia with this technique, which can present in several ways depending on the tissue affected. In our experience this complication is very rare and has only happened once where the patient presented with an acutely painful necrotic lesion on their buttock and subsequently required thrombolysis, antibiotics and surgical debridement.

Table 4.

Evidence for artery embolisation.

Advantages	Disadvantages	Evidence
•Minimally invasive with lower risk of non-target ischaemia than balloon occlusion techniques •Can target high-volume collaterals to the uterus and placenta, which may arise from anywhere in the pelvis •May preserve menstruation and fertility •Expedites placental resorption in cases using delayed placental removal.	•Minor complications: groin haematoma, uterine artery dissection, transient sciatic nerve paresis, post-embolisation syndrome •Major complications: uterine necrosis requiring hysterectomy, bladder gangrene, buttock necrosis, paraplegia •Multivessel embolisation can be time consuming based on degree of collateral vascularisation and level of experience of the interventional radiology physician.	Aggregated data currently only retrospective with heterogeneity in placenta management strategies and placenta accreta spectrum severity. Meta-analysis reports pooled intraoperative blood loss is less in placenta accreta spectrum cases with arterial embolisation than those without, and associated reduction in need for emergent hysterectomy.21 Uterine artery embolisation accelerates placental resorption with one study demonstrating a reduction in complete placental resorption from 32 to 17 weeks.37

Anaesthesia

This technique is usually performed under neuraxial anaesthesia, a CSE, but in emergent cases may be done under local anaesthetic with sedation or a general anaesthetic.

Interventional radiology

This technique requires a hybrid operating room suite. Before delivery of the infant, a 5-Fr sheath is placed in one of the femoral arteries. The infant is delivered through a hysterotomy positioned to avoid disrupting placental tissue. The hysterotomy is closed, then the abdominal surgical field is covered to allow fluoroscopy over the sterile field. Arterial supplies to the gravid uterus and placenta are identified using digital subtraction angiography. While the uterine artery is always a primary target, real-time angiography allows for identification of predominant pelvic collaterals that are unique to each patient. An embolising agent or combination of agents (most commonly polyvinyl alcohol in various sizes, and Gelfoam material made into a slurry) are injected into the arteries to block the blood flow.

The most common next step, particularly in severe PAS, is hysterectomy. However, several institutions are developing methods of delayed placental removal or other forms of uterine preservation with the intent of developing safe methods for fertility preservation.

Embolising agents can be soluble and absorbed within weeks of administration. During this time there is the potential for the uterus to be supplied by collateral circulation preventing ischaemia and preserving function to enable future pregnancy.³⁸

Artery ligation for uterine devascularisation in PAS

Evidence is emerging suggesting that internal iliac and uterine artery ligation is a possible alternative to IR techniques for uterine devascularisation in PAS.

One single-centre study examined 79 cases of Caesarean hysterectomy in patients with PAS. Some 47 seven patients underwent prophylactic endovascular balloon placement in the anterior division of the internal iliac arteries, and 32 underwent surgical ligation of the internal iliac arteries after classical Caesarean delivery. They concluded that the balloon group had a 10.6% complication rate (0% in the ligation group) and a longer total procedure time with no overall decrease in blood loss when compared with those in the surgical ligation group.³⁹ Despite the higher complication rate in the balloon group it was statistically not significant owing to small case numbers. A meta-analysis of 795 patients found that uterine artery ligation was superior to IIA ligation in terms of overall blood loss. Further to this the combination of uterine artery ligation with uterine tamponade resulted in a significant decrease in need for hysterectomy.⁴⁰

Challenges for anaesthesia in interventional radiology suite and hybrid operating theatres

If IR techniques are deemed essential from the beginning, the whole case should be performed in the IR suite or hybrid theatre and there are some important considerations for anaesthetists.

• (i)Remote site: the IR suite is remote from the maternity theatres and ward, and may be an unfamiliar site for maternity staff. The ready availability of qualified personnel, essential equipment (e.g. a Resuscitaire), uterotonic and other drugs and blood products need to be organised in advance.
• (ii)Ergonomics with a large team in a confined site: clearly defined roles and physical positions need to be identified before the procedure. A comprehensive team brief must be performed, with meticulous attention to the order of events and how to proceed if major haemorrhage or other adverse events occur (see Fig. 1).
• (iii)Radiation safety: the use of lead gowns and restricting to only essential personnel in theatre during the various stages of the procedure are needed to minimise the risk of radiation exposure to the patient, fetus and healthcare staff.
• (iv)Communication: assigning a team leader who maintains situational awareness is an important safety aspect. Clear communication within a team that knows each other well is key to planning for and minimising the consequences when major haemorrhage occurs.

Fig 1.

Diagram of equipment and team layout in 'hybrid' suite when managing a PAS case.

Conclusions

Although there is a paucity of prospective data to guide clinicians as to which endovascular approaches most effectively reduce morbidity while minimising non-target sequelae, emerging data suggest that both balloon occlusion and multivessel arterial embolisation techniques can reduce intraoperative blood loss and the need for emergency hysterectomy.

As we continue to strive for excellence in the management of PAS, collaborative well-designed prospective research efforts across PAS care centres are needed to generate systematic data guiding appropriate settings for balloon- or embolisation-based endovascular approaches. It is conceivable that different endovascular modalities will be useful in different settings, driven by the urgency of the case, grade of PAS disease, available expertise and IR resources at different centres.

The best outcomes are achieved when teams managing patients with PAS work together regularly, plan thoroughly for these cases and have clear leadership.

Finally, as years of clinical experience accrue and new evidence emerges in managing PAS, sharing best practice within specialist networks is vital to ensure we deliver the highest standard care to the broadest reach of patients with PAS.

Declaration of interests

The authors declare that they have no conflicts of interest.

MCQs

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Biographies

Kate Fletcher FRCA is a specialty registrar in anaesthesia at Guy's and St Thomas' NHS Foundation Trust, London.

Athansios Diamantopolous MD PhD EBIR FRCR FCIRSE is a consultant interventional radiologist at Guy's and St Thomas' NHS Foundation Trust and clinical lead for interventional radiology for PAS at St Thomas' Hospital. He is an honorary reader in imaging at Kings College and the deputy R&D lead for the directorate of Clinical Imaging and Medical Physics.

Jennifer Gilner MD PhD is a specialist in maternal-fetal medicine at Duke University Medical Center, Durham NC, USA.

Nhathien Nguyen-Lu BMedSci (Hons) FRCA is a consultant anaesthetist at Guy's and St Thomas' NHS Foundation Trust and has been lead anaesthetist at St Thomas' Hospital for PAS for the last 8 yrs. She has developed the service, which is now a recognised NHSE tertiary referral centre for PAS.

Matrix codes: 1I03, 2B05, 3B00