How do HELLP syndrome and pre‑eclampsia differ?

HELLP Syndrome vs. Preeclampsia: Key Differences

HELLP syndrome should be understood as a severe manifestation of preeclampsia rather than a completely separate disease entity, distinguished primarily by its specific laboratory triad of hemolysis, elevated liver enzymes, and low platelets. 1

Conceptual Relationship

• The American College of Cardiology and American Heart Association recommend viewing HELLP syndrome as part of the preeclampsia spectrum rather than a distinct disorder, which reduces clinical confusion and ensures comprehensive evaluation for all preeclampsia features when HELLP is identified. 1

• Preeclampsia is defined as new-onset hypertension (≥140/90 mmHg) at or after 20 weeks' gestation accompanied by proteinuria, renal insufficiency, liver involvement, neurological complications, hematological complications, or uteroplacental dysfunction. 1

• HELLP represents a specific constellation of laboratory abnormalities that signifies a more serious part of the preeclampsia spectrum, with higher maternal and perinatal mortality rates. 1

Diagnostic Distinctions

Preeclampsia Criteria

• Hypertension ≥140/90 mmHg developing at or after 20 weeks' gestation 1
• Proteinuria present in approximately 75% of cases 1
• May include various organ dysfunctions (renal, hepatic, neurological, hematological) 1

HELLP Syndrome Specific Criteria

• Hemolysis: Schistocytes on peripheral blood smear, elevated LDH >600 IU/L, or total bilirubin >12 mg/L 2, 3
• Elevated Liver enzymes: AST and ALT elevation indicating hepatic dysfunction 2
• Low Platelets: Platelet count <100,000/mm³ 2, 3

Critical Clinical Differences

Presentation Patterns

• HELLP can occur without hypertension in 15% of cases, making it diagnostically challenging compared to typical preeclampsia. 1
• HELLP can present without proteinuria, unlike classic preeclampsia definitions. 1
• 30% of HELLP cases occur or worsen postpartum (20% within 48 hours of delivery), whereas preeclampsia typically presents antepartum. 1, 4
• 10-20% of HELLP cases are diagnosed in the absence of preceding preeclampsia symptoms. 3

Symptom Specificity

• 65% of symptomatic HELLP patients present with right upper quadrant or epigastric pain, which should immediately trigger imaging for hepatic complications—this is more specific to HELLP than general preeclampsia. 1
• Abdominal pain or vomiting during the third trimester should raise suspicion for HELLP specifically. 3
• Neurological symptoms (headache, visual changes, hyperreflexia) occur in both conditions but predict eclampsia in 52% of HELLP cases. 1

Pathophysiologic Distinctions

• HELLP involves specific hepatic sinusoidal fibrin deposition causing obstruction and ischemia, which can progress to subcapsular hematomas, parenchymal hemorrhage, and hepatic rupture—complications more specific to HELLP than general preeclampsia. 1, 4

• The underlying endothelial dysfunction in HELLP triggers platelet aggregation and microangiopathic hemolysis through fibrin networks in small vessels, creating the characteristic schistocytes. 4

• LDH serves as a dual marker in HELLP, reflecting both hemolysis extent and hepatic dysfunction, making it one of the two best monitoring tools (along with platelet count) for disease progression. 4, 5

Prognostic and Management Implications

Severity and Outcomes

• HELLP carries dramatically increased maternal morbidity compared to isolated preeclampsia, with complications including eclampsia (52%), placental abruption, DIC, pulmonary edema, acute renal insufficiency, and subcapsular liver hematoma. 1, 3
• Maternal mortality with HELLP is 1.0-24.0% and perinatal mortality is 7.0-70.0%, significantly higher than uncomplicated preeclampsia. 5
• Delayed intervention in HELLP carries a 3.4% maternal mortality risk. 1

Management Differences

• Both conditions require delivery as definitive treatment, but HELLP mandates more aggressive pre-delivery stabilization including correction of coagulopathy with fresh frozen plasma and platelet transfusion if <50,000/mm³. 1, 2

• Regional anesthesia is contraindicated in HELLP with platelets <100,000/mm³ due to epidural hematoma risk, often necessitating general anesthesia—a consideration less relevant in preeclampsia without thrombocytopenia. 1, 2

• Abdominal imaging (ultrasound or CT) is mandatory in HELLP to rule out hepatic hemorrhage, infarct, or rupture, especially with right upper quadrant pain—not routinely required in uncomplicated preeclampsia. 1, 2

• HELLP requires level 3 hospital care with intensive care units for both mother and neonate, with invasive monitoring including central venous catheters for fluid management. 2, 3

Monitoring Distinctions

• Laboratory monitoring in HELLP must continue every 6-12 hours for at least 24-48 hours postpartum, as the syndrome peaks 24 hours after delivery and takes up to 10 days to fully resolve. 1, 4

• The degree of thrombocytopenia in HELLP correlates directly with liver dysfunction severity and predicts adverse maternal outcomes, requiring more intensive laboratory surveillance than preeclampsia alone. 1, 4

Common Pitfalls

• Do not delay delivery waiting for laboratory values to normalize in HELLP—the syndrome only resolves after delivery, and expectant management increases mortality risk. 1

• Do not assume hypertension or proteinuria must be present to diagnose HELLP—15% lack hypertension and many lack proteinuria. 1

• Do not overlook postpartum presentation—maintain high vigilance for 48-72 hours after delivery when 30% of cases occur or worsen. 1, 4

• Recognize that corticosteroids are ineffective for improving maternal HELLP outcomes, despite their use for fetal lung maturity before 34 weeks. 1, 3