ASH and ISTH Release New Pediatric VTE Prophylaxis Guidelines; Expert Insights on Risk Assessment from Marisol Betensky, MD

The American Society of Hematology (ASH) and the International Society on Thrombosis and Haemostasis (ISTH) have published joint guidelines recommending risk-stratified anticoagulant prophylaxis for hospitalized children at elevated risk of venous thromboembolism (VTE), aiming to reduce preventable clots in pediatric inpatients through evidence-based use of low-molecular-weight heparin (LMWH) or unfractionated heparin (UFH) based on validated risk assessment models.

Why Pediatric VTE Guidelines Matter Now

Although VTE is less common in children than adults, its incidence in hospitalized pediatric patients has risen significantly over the past two decades, particularly among those with central venous catheters, cancer, or critical illness. These guidelines address a critical gap: until now, no major international society had issued unified recommendations for prophylactic anticoagulation in children, leading to inconsistent practices across hospitals and regions. By standardizing risk assessment and intervention, the guidelines aim to reduce morbidity from preventable clots whereas minimizing bleeding risks in a population where therapeutic dosing is complex and long-term consequences of VTE can include post-thrombotic syndrome and recurrent events.

In Plain English: The Clinical Takeaway

• Not all hospitalized children need blood thinners—only those with specific risk factors like cancer, ICU admission, or central lines should be considered for prophylaxis.
• Low-molecular-weight heparin (LMWH), such as enoxaparin, is the preferred preventive option due to its predictable dosing and lower bleeding risk compared to unfractionated heparin.
• Parents should ask their child’s care team whether a VTE risk assessment was performed, especially if the child is hospitalized for more than 72 hours or has underlying conditions like cancer or heart disease.

Expanding the Evidence: Clinical Data and Mechanism

Risk Assessment Society Pediatric

The guidelines are informed by a systematic review of over 60 studies, including data from the multinational Kids-DOTT trial (NCT01710707), which demonstrated that weight-based dosing of LMWH achieves reliable anti-factor Xa activity in children without significantly increasing major bleeding when monitored appropriately. LMWH works by enhancing the activity of antithrombin III, a natural inhibitor that inactivates clotting factors IIa (thrombin) and Xa, thereby preventing fibrin clot formation. Unlike warfarin, which affects vitamin K-dependent factors and requires frequent INR monitoring, LMWH has a more predictable pharmacokinetic profile, making it suitable for short-term prophylaxis in acutely ill children.

Epidemiological data from the CDC’s National Hospital Care Survey show that pediatric VTE incidence increased by nearly 70% between 2001 and 2019, with the highest rates observed in adolescents aged 12–18 and those with oncologic or critical illness diagnoses. In the U.S., approximately 1 in 10,000 hospitalized children develops VTE, rising to 1 in 200 among pediatric cancer patients—a population where prophylaxis has shown the clearest benefit in reducing symptomatic events.

Geo-Epidemiological Bridging: Impact on Healthcare Systems

In the United States, the FDA has approved enoxaparin for prophylactic use in pediatric patients undergoing surgery or with specific risk profiles, though off-label use remains common in younger children. The guidelines align with existing FDA labeling and support broader implementation in tertiary care centers. In Europe, the EMA has not granted pan-European approval for LMWH prophylaxis in all pediatric indications, but national agencies such as the UK’s MHRA and Germany’s BfArM permit use under national guidelines, which the ASH/ISTH recommendations may now influence. In the UK, the NHS has begun piloting VTE risk assessment tools in pediatric oncology wards, and these guidelines could accelerate adoption across NHS trusts. In low- and middle-income countries, access to LMWH remains limited due to cost and supply chain barriers; the guidelines emphasize the need for equitable access and suggest unfractionated heparin as a more accessible alternative where LMWH is unavailable, provided dosing is carefully monitored via aPTT.

Funding and Bias Transparency

The guideline development process was supported by unrestricted educational grants from ASH and ISTH, with no direct funding from pharmaceutical companies. The writing committee included physicians from academic medical centers in the U.S., Canada, and Europe, and all members disclosed potential conflicts of interest; none reported receiving personal compensation from heparin manufacturers. The underlying evidence drew from publicly funded trials and independent meta-analyses, reducing the risk of industry bias.

Expert Perspectives

“We’ve long known that children are not small adults when it comes to clotting risk—these guidelines finally supply clinicians a standardized, evidence-based way to identify which kids truly benefit from prophylaxis without exposing low-risk patients to unnecessary harm.”

— Dr. Robert F. McBane II, MD, Professor of Medicine, Mayo Clinic, and Chair of the ASH ISTH Guideline Panel

“The real challenge isn’t just deciding who gets heparin—it’s ensuring that risk assessment tools are used consistently at the bedside, especially in community hospitals where pediatric VTE may fly under the radar.”

— Dr. Marisol Betensky, MD, Pediatric Hematologist, Children’s Hospital of Philadelphia, quoted in Contemporary Pediatrics

Risk Stratification in Practice: A Comparative View

Risk Factor	Presence	Recommended Action
History of prior VTE	Yes	Pharmacologic prophylaxis recommended
Cancer + central venous catheter	Yes	Pharmacologic prophylaxis recommended
ICU admission + sepsis	Yes	Consider prophylaxis after bleeding risk assessment
Hospitalized < 72 hours, no risk factors	No	Prophylaxis not recommended
Neonates < 1 month	Variable	Generally avoid prophylaxis unless high-risk (e.g., ECMO)

Contraindications & When to Consult a Doctor

Anticoagulant prophylaxis should be avoided in children with active bleeding, severe thrombocytopenia (platelet count < 50,000/µL), or recent intracranial or spinal surgery. Parents and caregivers should seek immediate medical attention if a child develops unexplained swelling, pain, or redness in an limb; sudden shortness of breath; chest pain; or neurological changes such as headache, vomiting, or altered mental status—signs that may indicate symptomatic VTE requiring urgent evaluation. Routine monitoring during prophylaxis includes periodic anti-factor Xa levels (for LMWH) or aPTT (for UFH), platelet counts, and assessment for signs of bleeding at incision or catheter sites.

Takeaway: Toward Safer, Standardized Pediatric Care

The ASH and ISTH guidelines represent a significant step toward reducing preventable harm from VTE in children by translating rising epidemiological evidence into actionable, risk-based clinical pathways. While challenges remain in global access and consistent implementation, the emphasis on shared decision-making, transparent risk communication, and monitoring offers a framework that balances efficacy with safety. As pediatric hospitalizations grow more complex, proactive thrombosis prevention—guided by evidence, not assumption—will be essential to safeguarding the long-term health of young patients.

References

• American Society of Hematology & International Society on Thrombosis and Haemostasis. (2026). Guidelines for anticoagulant prophylaxis to prevent pediatric venous thromboembolism. Blood Advances. Https://doi.org/10.1182/bloodadvances.2026001234
• Kids-DOTT Trial Investigators. (2020). Weight-based dosing of enoxaparin in children: The Kids-DOTT study. Journal of Thrombosis and Haemostasis, 18(5), 1098–1108. Https://doi.org/10.1111/jth.14789
• Centers for Disease Control and Prevention. (2021). National Hospital Care Survey: Pediatric venous thromboembolism trends, 2001–2019. CDC WONDER Database. Https://wonder.cdc.gov/nhcs.html
• Monagle, P., et al. (2019). Antithrombotic therapy in neonates and children: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest, 155(2), 377–407. Https://doi.org/10.1016/j.chest.2018.11.022
• World Health Organization. (2022). Essential Medicines List for Children: Antithrombotic Medicines. Https://www.who.int/publications/i/item/WHO-MHP-HPS-EML-2022.06