Although fortunately uncommon, abnormal placentation can result in massive haemorrhage at the time of delivery, with blood loss often reported of two to five litres and in some cases up to 20 litres.¹ Even in cases of planned caesarean hysterectomy, haemostasis can be difficult to obtain.

This occurs most notably with placenta percreta, when placental tissue has invaded beyond the uterus into surrounding structures, most commonly the bladder. Such complications of pregnancy are a well-recognised cause of maternal death.

An increasing number of centres now include interventional radiology (IR) as part of the delivery protocol when abnormal placentation is known or suspected, with the aim of reducing peripartum blood loss. The data supporting the use of IR mostly comes from case reports and small retrospective cohort studies.^2-6 While no single IR protocol has been demonstrated as the method of choice, there are a number of key principles that are important to ensure that the best use is made of IR in the peripartum period.

Vascular anatomy in abnormal placentation

Interventional radiology can help gain an understanding of the vascular anatomy in such cases, and why haemostasis can be so challenging in these patients. Figure 1 shows the vascular territories recruited in a patient with abnormal placentation. While internal iliac artery branch vessels (the uterine, internal pudendal and vesical) are often the dominant supply vessels, the uterus and placenta obtain extensive collateral supply from aortic (ovarian and ilio-lumbar) and external iliac (lateral circumflex iliac, inferior epigastric, ilio-lumbar, obturator and external pudendal) vascular territories. Figure 2 shows that even after emergency bilateral ligation of the internal iliac arteries for catastrophic haemorrhage, the placenta still derives significant arterial supply from aortic and external iliac artery collaterals.

Postpartum embolisation

Embolisation of the uterine arterial supply is the main IR treatment option for post-partum haemorrhage (PPH). First reported in 1979⁷, subsequent studies^4,8-14 have supported its use in patients haemodynamically stable enough to be transferred to IR. This technique has been shown to have good efficacy when compared to uterine compression sutures, iliac artery ligation or uterine devascularisation. In patients with placenta percreta, embolisation of collateral supply vessels may be necessary to ensure effective treatment. It is important to be aware that placental tissue that invades beyond the uterus, as shown in Figure 3, can be difficult to differentiate from the vascular supply to adjacent pelvic organs, including bladder and bowel, and requires an experienced interventional radiologist to avoid non-target embolisation.¹⁵

The guiding principle for patients with abnormal placentation should be to provide permanent distal occlusion of placental arterial supply beyond the main collateral supply arteries. This is best performed using particle embolisation similar to uterine artery embolisation for fibroids. In principle, distal embolisation will reduce the risk of ongoing bleeding from collateral supply that can occur with more proximal embolisation with coils. In patients with haemodynamic instability from ongoing bleeding, many centres will perform embolisation of the internal iliac artery with Gelfoam. This can be effective, but there remains a risk of ongoing bleeding from any collateral supply. Gelfoam embolisation is performed with the expectation of temporary vessel occlusion for three to six weeks, but it can result in permanent vessel occlusion, which is important to remember in this patient population. A decision to either ligate the internal iliac artery intra-operatively, or to embolise the internal iliac artery proximal to bleeding placental tissue, can make subsequent intervention for ongoing bleeding more complex. While we have found it feasible to embolise placental tissue for ongoing bleeding following intra-operative internal iliac artery ligation (Figure 2b), it requires the use of micro-catheters and a thorough understanding of aorto-iliac vascular anatomy.

Balloon occlusion for abnormal placentation

Pre-operative placement of occlusion balloons, first described for the aorta in 1995¹⁶ and subsequently for the internal iliac arteries¹⁴ was introduced with the goal of temporarily reducing uterine and placental blood flow, without the need for permanent iliac artery ligation. Since then, a small number of studies and case reports have been published.^1-5,16,17,18 However, probably because of the large number of factors contributing to individual patient blood loss, an unequivocal benefit with use of occlusions balloons has not been demonstrated.

Arterial sheath and balloon placement and management

In the absence of clear evidence supporting the use of occlusion balloons, there is a greater imperative to avoid complications. This requires well documented protocols that should cover the following.

Arterial sheath placement

Many centres will arrange for balloons to be placed by the interventional radiologist in the medical imaging department, with bilateral common femoral artery vascular sheaths. Following sheath placement, patient movement should be kept to a minimum, specifically hip flexion and patient rotation, to avoid displacement of the sheaths or balloons. If an epidural is planned this should be placed prior to transfer for placement of the balloons. If ureteric stent placement is required this can be more challenging to do prior to occlusion balloon placement, but it is preferable to balloon displacement. If ureteric stents are placed in the operating room with arterial sheaths in situ, then full lithotomy positioning should be avoided and the minimum amount of hip flexion possible used.

Balloon placement and inflation

The majority of interventional radiologists will use compliant balloons, which should reduce the risk of vessel injury (dissection or rupture). Non-compliant or standard angioplasty balloons are occasionally used, but can be difficult to match to the vessel lumen and, when mis-matched, can result in either poor vessel occlusion or even dissection.

With careful technique, placement of occlusion balloons in the angiography suite should result in minimal screening and radiation dose. Balloon inflation is most frequently performed following cutting of the umbilical cord, although some obstetricians will only request balloon inflation if haemostasis appears inadequate. Balloons should be removed on completion of the operation to reduce the risk of arterial thromboembolism. If embolisation is necessary because of ongoing bleeding, this can be done leaving the balloon catheters in situ, with the balloons deflated.

Post-operative management

The setting for postoperative care can vary greatly, from a general obstetric ward to an intensive care environment, depending on the patient’s post-operative status. It is important to have an agreed protocol regarding when, and by whom, arterial sheaths are to be removed. This protocol should be easily available in the patient’s notes. Sheaths left in situ for any length of time without proper care can result in significant complications and morbidity^7,15 resulting from arterial embolism. The practice in my unit is to remove all sheaths within two hours post-procedure unless postoperative embolisation is planned.

Multi-disciplinary management

Despite the trend of an increasing number of patients presenting with abnormal placentation¹⁹, most centres deal with a limited number of intermittent cases and it can be difficult to have a designated group of specialists available for each case. This is especially true because of the significant number of specialist teams that can be involved in addition to obstetrics, including gynae-oncology, anaesthesia, vascular surgery, urology, intensive care and interventional radiology. Nevertheless, it is important to identify a group of clinicians who have an interest in the management of abnormal placentation to allow development of a consistent approach to treatment and familiarity of team members. This facilitates the complex logistical planning when interventional radiology is required. Our hospital requires at least one multi-disciplinary team meeting, with all clinicians likely to be involved in the delivery present, to outline the management plan prior to the procedure.

Interventional radiology can provide important adjunctive support to this complex patient group, and specifically those patients at risk of significant or ongoing haemorrhage. Arterial embolisation has been used for over 30 years and appears to have good efficacy. Use of occlusion balloons is reasonable to consider, but requires coordinated multi-disciplinary management and well-documented, easily accessible protocols to ensure risks are minimised. Familiarity of all team members is critically important when dealing with a rapidly changing clinical situation, and this is greatly facilitated by a pre-operative multi-disciplinary meeting.