Background: The Hemorrhage Risk in Placenta Accreta
Placenta accreta spectrum (PAS) is a serious obstetric condition where the placenta abnormally invades the uterine wall, preventing normal detachment after delivery. This often leads to massive postpartum hemorrhage (PPH) – a leading cause of maternal mortality worldwide[1]. The incidence of placenta accreta has skyrocketed in recent decades, from about 1 in 30,000 pregnancies in the 1960s to roughly 1 in 500 in the 2000s[2]. This rise is largely due to increased cesarean deliveries (a major risk factor for accreta). When placenta accreta occurs, the potential blood loss during childbirth can be catastrophic[3]. Traditionally, life-saving measures like hysterectomy (surgical removal of the uterus) are employed, sacrificing fertility to control bleeding. In an effort to mitigate hemorrhage and preserve the uterus when possible, clinicians have explored prophylactic arterial balloon occlusion – essentially “turning off the tap” of blood flow to the uterus during delivery. Two main strategies have emerged: bilateral internal iliac artery balloon occlusion and abdominal aortic balloon occlusion. Below, we delve into how each approach works and compare their effectiveness and safety in the management of placenta accreta and severe PPH.
Why Use Prophylactic Balloon Occlusion?
The concept: By temporarily occluding key arteries right before or during a cesarean (usually a cesarean hysterectomy) for placenta accreta, doctors aim to reduce blood flow to the uterus and placental bed. Less inflow means less hemorrhage when the placenta is disrupted. This intervention is planned in advance for high-risk cases (e.g. known accreta or increta on imaging). It is performed by inserting balloon-tipped catheters into the arteries before incision and inflation of the balloons at the critical moment to restrict blood flow.
- Internal Iliac Artery Occlusion: Interventional radiologists place balloons in both internal iliac arteries (the main pelvic arteries supplying the uterus). Inflating these balloons limits uterine arterial inflow from the pelvis. The goal is to reduce bleeding during placental removal or uterine surgery.
- Aortic (Abdominal) Occlusion: A larger balloon is placed in the abdominal aorta (usually below the renal arteries, above the takeoff of the pelvic arteries). Inflation here completely halts blood flow to the lower body (including uterus and pelvis) for a short time. This is essentially the obstetric application of REBOA (Resuscitative Endovascular Balloon Occlusion of the Aorta), a technique borrowed from trauma surgery. By “clamping” the aorta internally, one can dramatically slow hemorrhage from any pelvic source.
Both methods have the same intent – to prevent exsanguinating blood loss – but they differ in scope of occlusion and technical complexity. Below we examine each approach’s track record.
Internal Iliac Artery Balloon Occlusion: Mixed Results
Bilateral internal iliac artery balloon occlusion (IIABO) has been used for decades in high-risk obstetrics, but the evidence for its efficacy is mixed. Intuitively, reducing uterine arterial inflow via the internal iliacs should curb hemorrhage. Some early reports and small series suggested benefits, but larger studies have struggled to demonstrate a clear advantage.
A 2021 systematic review pooled 15 studies (over 1,000 women) and found no statistically significant differences in outcomes between women who received prophylactic internal iliac balloons and those who did not[4]. Specifically, estimated blood loss and transfusion requirements were similar with or without internal iliac occlusion[5][4]. There was also no significant impact on rates of hysterectomy or ICU admission in that analysis. In other words, blocking the internal iliac arteries did not reliably translate into less bleeding or fewer blood transfusions for placenta accreta patients.
Why might internal iliac occlusion underperform? One reason is the rich collateral circulation in the obstetric pelvis. The uterus can also receive blood from ovarian arteries and other collateral vessels that aren’t controlled by the internal iliac balloons. If those “back channels” continue supplying the uterus, hemorrhage may still be profuse. Indeed, experts have postulated that occluding more proximally (at the aorta) could be more effective specifically because it minimizes the chance for collateral perfusion to bypass the blockage[6]. Additionally, internal iliac balloon placement is technically demanding – it requires cannulating both iliac arteries under fluoroscopic guidance, which can be time-consuming and exposes mother and fetus to radiation. In fact, one meta-analysis noted that fetal radiation exposure was higher during internal iliac balloon procedures than with aortic occlusion[7].
On a positive note, internal iliac occlusion is a localized intervention, so in theory it avoids cutting off blood flow to the entire lower body. Occluding only the uterine/pelvic circulation might reduce the risk of lower extremity ischemia compared to an aortic occlusion. However, the literature suggests that serious complications with internal iliac balloons are still possible (e.g. arterial injury or clot formation at the catheter site), and the overall complication rate is not negligible. Reported adverse event rates hover around a few percent. For example, in a compilation of studies, about 2% of women experienced complications related to prophylactic iliac balloon placement[8][9] – most commonly thrombus (clot) formation in the artery. We’ll discuss safety in more detail shortly.
In summary, while prophylactic internal iliac artery balloons are conceptually appealing and have been utilized in many centers, robust evidence has not shown a clear reduction in hemorrhage or transfusions with their use[4]. Due to collateral blood flow and logistical challenges, their impact may be limited in placenta accreta cases. This has driven interest toward a more complete occlusion strategy – the aortic balloon.
Aortic Balloon Occlusion (REBOA): A Broader “Off Switch”
Aortic balloon occlusion involves temporarily inflating a balloon in the abdominal aorta, which comprehensively stops arterial inflow to the pelvis (and legs) during a hemorrhage. In trauma medicine, REBOA has been a game-changer for controlling internal bleeding; now obstetric teams are adapting it for severe PPH and accreta cases. By occluding the aorta (typically in the infrarenal segment, also known as “Zone III” REBOA in trauma terminology), blood flow to the uterus, pelvic organs, and lower extremities is momentarily halted, giving surgeons a crucial window to intervene – be it delivering the baby, resecting the placenta, or proceeding with hysterectomy – with dramatically reduced bleeding.
Effectiveness: Emerging evidence suggests that aortic occlusion is highly effective at reducing blood loss in placenta accreta surgeries. A 2021 meta-analysis directly comparing abdominal aortic (AA) balloons versus internal iliac (IIA) balloons found that aortic occlusion yielded significantly less intraoperative hemorrhage – on the order of 400 mL less blood loss on average, compared to the iliac occlusion group[7]. The authors concluded that aortic occlusion was more effective in reducing blood loss than internal iliac occlusion in PAS patients[10].
Looking at prophylactic aortic occlusion versus doing nothing (no balloon), the advantage is even more striking. A recent network meta-analysis (50 studies, ~6,000 women) reported that proximal aortic balloon occlusion was associated with over 1,000 mL less blood loss on average during accreta cesarean deliveries, whereas distal (iliac) occlusion was associated with ~400 mL less blood loss[11]. In other words, the aortic approach appeared to spare an extra liter of blood compared to cases with no occlusion – roughly double the benefit seen with internal iliac balloons[11]. This substantial reduction can be the difference between a routine transfusion and a life-threatening hemorrhage in a high-risk delivery.
Real-world clinical results are also encouraging. A 2023 cohort study of patients with invasive placenta (accreta/increta) showed dramatic improvements when REBOA was used prophylactically. In that study (278 women with REBOA vs 86 without), the median estimated blood loss was about 1.37 liters with REBOA vs 3.54 liters without – essentially a 60% reduction in hemorrhage volume[12]. Importantly, 95% of women in the REBOA group kept their uterus, versus only 27% in the no-REBOA group (who more often required emergency hysterectomy due to uncontrollable bleeding)[12]. The REBOA group also had significantly shorter operating times and fewer ICU admissions[12]. These are remarkable outcome differences, suggesting that a well-timed aortic occlusion can transform an otherwise dire situation. By controlling bleeding, surgeons were able to work more quickly and even pursue uterine-preserving treatments in many cases – a huge win for patients desiring future fertility.
It’s worth noting that the radiation exposure to the fetus and mother can be lower with aortic occlusion as well. Because only a single catheter is placed (often with ultrasound guidance for femoral access and limited fluoroscopy for positioning), the fluoroscopy time tends to be short. In the meta-analysis by Liu et al., the fetal radiation dose was significantly lower in the aortic balloon group compared to the internal iliac group[7]. This is an added benefit when considering the baby’s safety during these interventions.
Practical advantages: From a logistical standpoint, an aortic balloon occlusion requires only one arterial puncture (usually one femoral artery) to occlude both uterine arteries (indeed, all pelvic arteries) at once. In contrast, achieving bilateral internal iliac occlusion necessitates catheterizing two arteries (often both femoral arteries or both common iliacs) and maneuvering balloons into each internal iliac – a more complex endovascular feat. The aortic approach can therefore be faster to deploy in an urgent scenario. In one analysis, the duration of balloon inflation needed was shorter in the aortic group than in the iliac group (by about 5 minutes on average)[7], implying more efficient hemorrhage control. Furthermore, occluding at the aorta eliminates concerns about missed collateral circulation; as one publication noted, the proximal occlusion effect is less countered by collaterals than distal occlusion[6].
Safety and Considerations: Risks vs. Rewards
Whenever blood flow is stopped, even temporarily, there are important safety considerations. Both internal iliac and aortic balloon occlusion carry risks such as arterial injury, thrombosis (clot formation), and ischemia to tissues. How do the two approaches compare in this regard?
Reassuringly, complication rates reported for prophylactic balloon occlusion in accreta cases are relatively low for both techniques. The 2024 systematic review found that roughly 2% of women experienced adverse events related to the prophylactic balloon procedure, and this rate was similar between the distal (iliac) and proximal (aortic) occlusion groups[13]. The most common issue was thrombus formation at the catheter site (e.g. a clot in the femoral or iliac artery)[8][9]. These clots can usually be managed if detected – for example, by giving blood thinners, or by surgical thrombectomy if needed. It’s notable that in the direct comparison meta-analysis, there was no statistically significant difference in lower extremity thrombosis rates between aortic and internal iliac occlusion groups[14]. In other words, when done carefully, aortic REBOA was no more likely to cause leg ischemia or clots than internal iliac balloons – a testament to improvements in technique and device design.
That said, some early studies of REBOA in obstetrics did report complications. For instance, one smaller retrospective study (16 REBOA vs 75 controls) found a higher incidence of arterial thromboses in the REBOA group and no clear reduction in blood loss[15]. However, this study’s sample size was limited, and it likely reflected an earlier learning curve (or use of larger-diameter catheters). With modern low-profile devices and experienced teams, outcomes appear to have improved significantly – as evidenced by the larger series showing major hemorrhage reduction without excess complications[12][13].
Mitigating the risks: Key to safe aortic occlusion is limiting the occlusion time and maintaining meticulous coordination among the surgical team. Unlike internal iliac balloons, an aortic balloon literally stops blood to everything below it – so it cannot stay inflated indefinitely without causing ischemic injury. Typically, teams will inflate the aortic balloon for short intervals (e.g. 5-10 minutes at a time) to stem bleeding, then deflate to allow some reperfusion, and repeat as needed[16]. This cyclical occlusion technique can prevent prolonged ischemia to the legs and pelvic organs while still controlling hemorrhage. In the Spanish case of planned REBOA for placenta accreta, for example, the team used 7-minute inflations with 2-minute release intervals, and achieved bleeding control with no complications[17][16]. Close communication between obstetric surgeons, anesthesiologists, and the interventionalist or surgeon managing the balloon is essential so that everyone knows when the balloon is up or down. Monitoring of distal pulses and blood pressure helps ensure timely deflation before any damage occurs.
Another safety improvement has been the advent of lower-profile REBOA devices. Older REBOA catheters required large introducer sheaths (7–12 French, roughly 3–5 mm in diameter), which carry higher risks of arterial trauma. Today, new devices are as small as 4 French (~1.3 mm). For instance, the COBRA-OS® is a 4-Fr aortic occlusion catheter, currently the smallest FDA-cleared REBOA device[18]. Such a slim profile can be inserted more easily into postpartum patients’ often constricted blood vessels, with a lower risk of puncture site complications. The COBRA-OS and similar next-generation REBOA tools were specifically designed to make aortic occlusion safer and faster in emergencies like PPH. Early reports indicate that using these devices in obstetrics is yielding promising outcomes with minimal added risk[19]. As Dr. Adam Power (vascular surgeon and co-inventor of COBRA-OS) noted, the goal is fewer transfusions, fewer emergency hysterectomies, and ultimately, reduced maternal deaths by “turning off the tap” of bleeding when needed[19].
Conclusion: Aortic Occlusion Emerges as the Preferred Option
When it comes to preventing hemorrhage in placenta accreta and other high-risk obstetric cases, the evidence to date leans in favor of aortic balloon occlusion as the more effective strategy. Bilateral internal iliac balloon occlusion, while theoretically useful and still employed in some centers, has not consistently shown significant benefits in reducing blood loss or transfusion requirements[4]. In contrast, occluding the abdominal aorta (using REBOA) provides a more complete halt of blood flow, translating into substantially less hemorrhage intraoperatively[11] and improved clinical outcomes[12] in many reports. In practical terms, aortic occlusion can simplify the procedure (single catheter vs. two) and may involve shorter occlusion times and less radiation exposure[7].
Of course, no intervention is without risk – careful patient selection, thorough planning, and multidisciplinary expertise are vital. Both approaches have low but real complication rates (~2% in experienced settings)[13], emphasizing that these procedures should be done by skilled teams with vascular or interventional radiology support. Yet, with modern techniques, aortic REBOA has shown that it can be deployed prophylactically in a controlled manner to avert catastrophe when faced with a invasive placenta. Notably, it can even enable the holy grail of accreta management: controlling hemorrhage and preserving the uterus in some cases[12].
For clinicians preparing to manage placenta accreta spectrum disorders, it’s important to weigh the options. Internal iliac balloons might seem less extreme, but the literature questions their utility. Aortic balloon occlusion, on the other hand, is gaining traction as a prophylactic measure that can markedly reduce blood loss and give the surgical team critical control. Devices like the 4-Fr COBRA-OS® now make aortic occlusion more accessible than ever, by offering rapid, low-profile deployment tailored to obstetric patients. While we should remain cautious and continue to gather data (ideally from prospective trials) on these interventions, the current trend is clear. Proximal aortic control is emerging as the superior option for managing placenta accreta and severe PPH prophylactically – providing a powerful safety net in one of obstetrics’ most dangerous situations.
References:
- Liang D, et al. Eur J Radiol. 2021 – Internal iliac artery balloon occlusion vs no occlusion in placenta accreta (Meta-analysis)[4].
- Liu C, et al. Clin Imaging. 2021 – Abdominal aortic vs internal iliac balloon occlusion in PAS (Meta-analysis)[7][10].
- Bonsen LR, et al. Obstet Gynecol. 2024 – Prophylactic radiologic interventions in placenta accreta (Network meta-analysis)[11][6].
- Ye Y, et al. BMC Pregnancy Childbirth. 2023 – REBOA efficacy in invasive placenta (Cohort study)[12].
- Müller B, et al. Obstet Gynecol. 2023 – Outcomes in placenta accreta with REBOA vs no REBOA (Retrospective study)[15].
- van den Akker T, et al. (cited in Bonsen 2024) – Discussion of collaterals and occlusion effectiveness[6].
- Front Line Medical Technologies (Press) – COBRA-OS device profile (4-French REBOA)[18].
- MDDI Online – Interview with Dr. Adam Power on postpartum hemorrhage and aortic occlusion[19][3].
- StatPearls – Placenta Accreta incidence trends[2].
- ACOG/SMFM – Placenta accreta spectrum and hemorrhage risk (Background info)[1][3].
[1] [3] [18] [19] Understanding Arterial Occlusion System Use for Safer Postpartum Hemorrhage Treatment
[2] Placenta Accreta – StatPearls – NCBI Bookshelf
https://www.ncbi.nlm.nih.gov/books/NBK563288/
[4] [5] Internal iliac artery balloon occlusion in the management of placenta accreta: A systematic review and meta-analysis – PubMed
https://pubmed.ncbi.nlm.nih.gov/33910145/
[6] [8] [9] [11] [13] Obstetrics & Gynecology
[7] [10] [14] Efficacy and safety of prophylactic abdominal aortic balloon occlusion versus internal iliac arterial balloon occlusion for placenta accreta spectrum disorder: A systematic review and meta-analysis – PubMed
https://pubmed.ncbi.nlm.nih.gov/34171597/
[12] Efficacy of resuscitative endovascular balloon occlusion of the aorta for hemorrhage control in patients with abnormally invasive placenta: a historical cohort study | BMC Pregnancy and Childbirth | Full Text
https://bmcpregnancychildbirth.biomedcentral.com/articles/10.1186/s12884-023-05649-8
[15] Maternal Outcomes in Placenta Accreta Spectrum Disorders Managed With REBOA [ID: 1370002]
[16] [17] REBOA in Obstetrics: Europe’s First COBRA-OS® Case Sets New Precedent |
https://frontlinemedtech.com/reboa-in-obstetrics-europes-first-cobra-os-case-sets-new-precedent/
