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Pre-eclampsia & Eclampsia for USMLE Step 1

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Pre-eclampsia & Eclampsia for the USMLE Step 1 Exam
Definition and Classification
  • Pre-eclampsia
    • Pre-eclampsia is a pregnancy-related hypertensive disorder defined by new-onset hypertension and either proteinuria or end-organ dysfunction after 20 weeks of gestation.
  • Eclampsia
    • Eclampsia is the occurrence of new-onset, generalized tonic-clonic seizures in a woman with pre-eclampsia and without any other identifiable cause for seizures.
  • Classification of Pre-eclampsia
    • Mild Pre-eclampsia: Blood pressure ≥140/90 mmHg on two separate occasions with proteinuria (≥300 mg in a 24-hour urine collection).
    • Severe Pre-eclampsia: Blood pressure ≥160/110 mmHg and one or more severe features:
    • Severe proteinuria (≥5 g/24 hours) or end-organ dysfunction such as thrombocytopenia, elevated liver enzymes, renal impairment, pulmonary edema, or neurologic symptoms like headache and vision changes.
Epidemiology and Risk Factors
  • Epidemiology
    • Affects approximately 3-5% of pregnancies and is a leading cause of maternal and perinatal morbidity and mortality.
  • Risk Factors
    • Advanced maternal age, nulliparity, obesity, family history of pre-eclampsia, and history of pre-eclampsia in a previous pregnancy.
    • Chronic hypertension, diabetes, renal disease, autoimmune disorders, and multiple gestations are also associated with increased risk.
Pathophysiology
  • Abnormal Placental Development
    • Inadequate remodeling of the spiral arteries reduces placental blood flow, leading to placental ischemia and hypoxia.
    • Ischemia stimulates the release of anti-angiogenic factors (e.g., soluble fms-like tyrosine kinase-1 or sFlt-1) and inflammatory cytokines that disrupt endothelial function.
  • Systemic Endothelial Dysfunction
    • Imbalance in pro- and anti-angiogenic factors leads to widespread vasoconstriction, increased vascular permeability, and capillary leakage.
    • This systemic endothelial damage contributes to hypertension, proteinuria, and multi-organ effects (e.g., renal, hepatic, cerebral).
Clinical Manifestations
  • Hypertension
    • Systolic BP ≥140 mmHg or diastolic BP ≥90 mmHg on two separate readings, with onset after 20 weeks of gestation.
  • Proteinuria
    • Defined as ≥300 mg in a 24-hour urine collection or a protein-to-creatinine ratio of ≥0.3.
    • Severe proteinuria is an indicator of worsening disease but is not required for diagnosis if end-organ damage is present.
  • Severe Symptoms and End-Organ Dysfunction
    • Neurologic symptoms include severe headache, blurred vision, scotomas, and hyperreflexia.
    • Epigastric or right upper quadrant pain may indicate hepatic involvement.
    • Renal dysfunction manifests as oliguria and elevated serum creatinine.
  • Seizures (Eclampsia)
    • Tonic-clonic seizures typically occur in patients with severe pre-eclampsia and are life-threatening.
Diagnosis
  • Blood Pressure Measurement
    • Accurate measurement is essential, with BP recorded on at least two occasions.
  • Urine Testing for Protein
    • 24-hour urine collection or a spot urine protein-to-creatinine ratio are used for diagnosing proteinuria.
  • Laboratory Evaluation
    • CBC: To evaluate for thrombocytopenia.
    • Liver Function Tests (LFTs): Assess for elevated liver enzymes.
    • Renal Function Tests: Monitor serum creatinine and uric acid.
Management
  • Delivery as Definitive Treatment
    • The only cure for pre-eclampsia/eclampsia is delivery, which is recommended at 37 weeks for mild cases or as soon as possible in severe cases or eclampsia.
  • Antihypertensive Therapy
    • Used for blood pressures ≥160/110 mmHg.
    • Common agents include labetalol, hydralazine, and nifedipine.
  • Seizure Prophylaxis with Magnesium Sulfate
    • Magnesium sulfate is administered for seizure prevention in severe pre-eclampsia and to treat seizures in eclampsia.
    • Dosage includes a 4-6 g IV loading dose, followed by a maintenance dose of 1-2 g per hour.
  • Corticosteroids for Fetal Maturity
    • Administered when preterm delivery is anticipated (<34 weeks) to enhance fetal lung development.
Complications
  • Maternal Complications
    • Eclampsia, HELLP syndrome (Hemolysis, Elevated Liver enzymes, Low Platelets), placental abruption, and stroke.
  • Fetal Complications
    • Preterm birth, intrauterine growth restriction (IUGR), hypoxia, and stillbirth, primarily due to placental insufficiency.
Key Points
  • Pre-eclampsia is characterized by new-onset hypertension and proteinuria or end-organ dysfunction after 20 weeks of gestation.
  • Eclampsia refers to pre-eclampsia with the occurrence of seizures.
  • Risk Factors include advanced age, nulliparity, chronic hypertension, and autoimmune disorders.
  • Pathophysiology: Abnormal placental development leads to placental ischemia, resulting in widespread endothelial dysfunction and multi-organ involvement.
  • Clinical Manifestations:
    • Severe symptoms include headache, visual changes, right upper quadrant pain, and renal impairment.
  • Management:
    • Delivery is the definitive treatment.
    • Antihypertensives control severe hypertension, and magnesium sulfate is used for seizure prophylaxis.
    • Corticosteroids are administered to promote fetal lung maturity in cases requiring early delivery.
  • Complications include eclampsia, HELLP syndrome, placental abruption, and fetal growth restriction.

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