Acute respiratory distress syndrome (ARDS), initially described as a severe complication in critically ill patients, is characterized by bilateral pulmonary infiltrates and acute hypoxemia unrelated to heart failure (1). Prone positioning ventilation is one of the few interventions proven to reduce mortality in mechanically ventilated ARDS patients (2). Although complications during prone positioning are recognized, abdominal wall hematoma is clinically rare and often presents non-specifically as an abdominal mass, acute pain, distension, or hypotension (3). Post-cesarean abdominal wall hematoma is an uncommon surgical complication; delayed diagnosis may lead to severe outcomes, including prolonged recovery, life-threatening events, and increased healthcare burden (4). We report a case of abdominal wall hematoma occurring during prone positioning ventilation under venovenous extracorporeal membrane oxygenation (VV-ECMO) support in a postpartum ARDS patient. Although the outcome was favorable, this rare complication warrants clinical vigilance.

A 42-year-old woman (gravida 3, para 1, with one prior cesarean delivery) was transferred to our hospital at 26 weeks’ gestation with a 1-month history of cough and sputum. Initial tests for SARS-CoV-2, influenza A, and influenza B were negative, and community-acquired pneumonia was diagnosed. Despite 5 days of oral azithromycin (500 mg/day), symptoms worsened. On February 29, 2024, she was admitted to the high-risk maternity center and subsequently transferred to the ICU following multidisciplinary assessment (Figure 1).

Abdominal wall hematoma during prone positioning under VV-ECMO is exceptionally rare. Although our patient recovered, this complication could have precipitated ECMO circuit thrombosis if it occurred earlier, increasing morbidity and costs. In the context of respiratory pandemics, this warrants heightened awareness.

Approximately 0.1–0.2% of pregnancies are complicated by respiratory failure. Physiological changes increase susceptibility to hypoxemia, which may adversely affect the fetus (5). ARDS is a leading cause of non-obstetric mortality in pregnancy (5, 6), though its incidence remains low (7). Our patient’s rapid progression to ARDS underscores the need for vigilance in similar cases.

Prone positioning, used since 1976 for ARDS (8, 9), improves oxygenation when lung-protective ventilation fails (10). Data in late pregnancy are limited to case reports (11). Our patient benefited significantly from prone positioning only after delivery, suggesting its early application in gestational ARDS may be advantageous.

Management of ARDS often requires mechanical ventilation. However, in pregnant patients receiving mechanical ventilation, excessive ventilation and alkalosis should be avoided to prevent uterine vasoconstriction, while hyperventilation and hypercapnia should be minimized to avert fetal respiratory acidosis. Additionally, maternal PaO₂ should be maintained above 70 mmHg to ensure adequate fetal oxygenation (5). Importantly, due to the rarity of ARDS in pregnancy prior to the pandemic, management strategies for respiratory compromise in this population were largely extrapolated from non-pregnant patients.

For ARDS patients managed with mechanical ventilation employing high PEEP, low tidal volume, low plateau pressure, and permissive hypercapnia, the therapeutic cornerstone remains ventilator synchronization using sedation combined with prone positioning ventilation. Prone positioning has been utilized during pregnancy and reported in case series (12–15). It improves ventilation-perfusion matching, reduces compression of the posterior and medial lungs, thereby diminishing hypoxic vasoconstriction, enhancing cardiac output, and recruiting additional alveolar units. Although randomized controlled trials are lacking, documented complications in standard ARDS patients include barotrauma, bleeding, transient hypotension, and transient hypoxemia (16), all potentially detrimental to the fetus. The need for delivery should be coordinated with neonatologists and obstetricians. Based on our prior experience and this case, timely termination of pregnancy becomes paramount when maternal condition deteriorates. Most intensivists possess limited experience managing pregnant patients with ARDS. Nevertheless, the fundamental management goals for all ARDS patients are consistent: optimizing oxygenation and maintaining perfusion and cardiac output. Crucially, potential adverse effects of therapy on the fetus must be considered to ensure the survival of both mother and fetus under the threat of hypoxemia.

VV-ECMO is reserved for refractory hypoxemia/hypercapnia (17, 18). Pre-ECMO prone positioning correlates with better outcomes (18), but delayed ECMO initiation risks irreversible lung injury. Delivery timing remains challenging. For patients >30–32 weeks with progressive respiratory failure, early delivery should be considered (19, 20). In our case, multidisciplinary debate prioritized maternal safety over fetal gestation extension. Given the gestational age of only 27 weeks, the obstetrics and neonatology teams advocated prolonging the pregnancy to enhance fetal viability. However, from the intensive care perspective, continuing the pregnancy posed extreme risks to both mother and fetus. Thus, in such scenarios, intensivists should prioritize maternal safety and advocate for timely pregnancy termination.

Cases of thoracic hemorrhage have been reported in COVID-19 (21). Management of postpartum abdominal wall hematoma lacks established guidelines. These hematomas are classified as subcutaneous, subfascial, or extraperitoneal. Subcutaneous hematomas involve superficial bleeding, presenting as wound oozing or ecchymosis, and are readily detectable. Subfascial and extraperitoneal hematomas are deeper and often identified later. Extraperitoneal hematomas, developing within loose connective tissue, can expand significantly, forming large collections. Patients typically present with low-grade fever; examination may reveal swelling, widening, and tenderness around the incision. Diagnosis is confirmed by aspiration of blood or ultrasound. Large extraperitoneal hematomas can cause marked abdominal distension, anemia disproportionate to visible blood loss, and potentially life-threatening hemorrhagic shock (22). Hematomas < 5 cm in diameter, if localized with no active bleeding, can be managed conservatively with infection prophylaxis and observation. Active bleeding, signs of infection, or anticipated low success with conservative management warrant aggressive intervention, such as endovascular embolization (23) or surgical evacuation with meticulous hemostasis and drainage if needed (24). In our patient, hematoma development during prone positioning necessitated anticoagulation hold—a precarious situation during ECMO. Fortunately, the outcome was favorable.

Prone positioning ventilation in patients with recent abdominal surgery or during pregnancy remains challenging. Some consider it a relative contraindication (25, 26). Clinicians face the core dilemma of balancing the potential benefits of prone positioning against complication risks in such ARDS patients. Strategies like reducing prone duration, alternating prone/lateral positioning, or using neuromuscular blockade to reduce intra-abdominal pressure during proning require validation through prospective studies.

The timing of heparin anticoagulation initiation in our patient (12 h post-cesarean) prompted extensive discussion. During ECMO, the balance between thrombosis and hemorrhage is a daily concern. Contact between blood and the non-biological circuit surface activates coagulation pathways, consuming both procoagulant and anticoagulant factors, thereby increasing the patient’s risk for both thrombosis and bleeding (27). Consequently, routine anticoagulation is essential for ECMO patients, with the explicit goal of preventing bleeding in vivo and clotting ex vivo. Due to the inherent complexity of ECMO patients, guidelines lack uniform recommendations for anticoagulation targets. The 2021 ELSO Anticoagulation Guideline (28) advocates for rational interpretation of Activated Clotting Time (ACT) values over rigid targets. Suggested targets include maintaining Activated Partial Thromboplastin Time (aPTT) at 1.5–2.5 times baseline or 60–90 s, and anti-Factor Xa levels between 0.3–0.7 IU/mL (with unchanged heparin dose if within range). Chinese expert consensus (29) recommends aPTT 40–55 s, ACT 180–220 s, and anti-Factor Xa 0.3–0.7 IU/mL for most patients. Therefore, anticoagulation requires individualized management, with clinicians adjusting targets daily based on the patient’s evolving clinical status, bleeding manifestations, and coagulation parameters.

Maternal prone abdominal wall hematoma found during VV-ECMO is rare and prone to adverse outcomes. We remind clinicians to be aware of this rare complication and prevent it.