This page summarizes common pathways; always follow your institution’s protocol, local pharmacy concentrations, and clinician judgment.
Prevention Diagnosis Severe features Magnesium Acute HTN References

Preeclampsia prevention

Low-dose aspirin risk-based prophylaxis; calcium supplementation when dietary intake is low.
Low-dose aspirin — indications (risk-based)
Who to treat, timing, and risk tiers (USPSTF / ACOG/SMFM / NICE framing).
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Evidence/benefit: Low-dose aspirin started in the late first/early second trimester reduces the risk of preeclampsia and related outcomes in patients at increased risk. USPSTF notes benefit with doses studied 60–150 mg/day initiated 12–28 weeks, with harms considered no greater than small.
USPSTF (2021): Aspirin Use to Prevent Preeclampsia

Who should receive aspirin prophylaxis?

Risk tier Examples Typical action
High risk
Any ONE factor
  • History of preeclampsia (especially with adverse outcome)
  • Multifetal gestation
  • Chronic hypertension
  • Pregestational diabetes (type 1 or 2)
  • Chronic kidney disease / renal disease
  • Autoimmune disease (e.g., SLE, antiphospholipid syndrome)
 Recommend
Start 12–28 w (ideally <16), continue until delivery (or per local pathway).
Moderate risk
Typically ≥2 factors
  • Nulliparity
  • Age ≥ 35 years
  • BMI > 30 kg/m²
  • Family history of preeclampsia (mother or sister)
  • Interpregnancy interval > 10 years
  • Prior adverse pregnancy outcome (e.g., SGA/low birthweight)
  • In vitro fertilization
  • Lower income or other social vulnerability markers (risk markers, not biology)
  • Black race as a risk marker reflecting structural inequities (not biological determinism)
 Consider
Shared decision-making (many pathways treat “≥2” as treat).
Not increased risk No high-risk factor and fewer than typical threshold of moderate-risk factors. Routine aspirin prophylaxis is generally not recommended.

Helpful links: USPSTF (2021)  |  ACOG/SMFM Practice Advisory (Dec 2021)  |  ACOG CO 743  |  NICE NG133

Practical low-dose aspirin dosing guidance
Start window, bedtime option, adherence tips, what to do if missed.
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Start 12–28 weeks gestation (often “ideal” to start before 16 weeks if possible).

Dose U.S. commonly 81 mg once daily. NICE uses a range 75–150 mg once daily.

Time of day Many clinicians suggest taking aspirin in the evening/at bedtime (helps routine adherence; some trials used bedtime dosing). If morning is more reliable, morning is acceptable — adherence matters most.

With food? If dyspepsia occurs, take with food or after a snack.

Patients should use only one “low-dose” aspirin product daily. Avoid adding other NSAIDs unless specifically directed.

Contraindications, cautions, and peripartum considerations
Allergy/bronchospasm, bleeding risk, concomitant anticoagulation, neuraxial policy varies.
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Do NOT use
  • Severe aspirin/NSAID hypersensitivity (e.g., anaphylaxis/angioedema)
  • Aspirin-exacerbated respiratory disease / aspirin-triggered bronchospasm
  • Clinician-directed avoidance due to a specific high-risk bleeding condition
Use caution / coordinate care
  • Active significant GI bleeding or recent severe GI bleed
  • Severe thrombocytopenia or known bleeding disorder (individualize)
  • Concomitant anticoagulation (e.g., LMWH) — coordinate timing/anesthesia plans
  • Planned procedure where the proceduralist requests holding antiplatelets (follow local policy)
Stop date Many U.S. pathways continue low-dose aspirin until delivery. Some institutions stop at a defined GA (e.g., 36 weeks) for workflow reasons. Follow your institution’s anesthesia/OB protocol.

Neuraxial anesthesia: Low-dose aspirin alone is typically not a contraindication, but policy depends on local anesthesia guidance and overall bleeding risk.

Counseling
What it’s for, expected benefit, safety signals, and when to call.
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  • Purpose: Helps lower the chance of developing preeclampsia and related complications.
  • Safety: At low doses, large studies show harms are small for most patients when appropriately selected (follow clinician guidance).
  • Call your clinician urgently for:
    • Hives, swelling, wheezing, or trouble breathing after taking aspirin
    • Black/tarry stools, vomiting blood, or other significant bleeding symptoms
  • Do not add other NSAIDs (ibuprofen/naproxen) routinely without clinician guidance.
Calcium supplementation (selected settings)
Most useful where dietary calcium intake is low (WHO often cited). Consider total calcium (diet + supplement).
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When to consider In populations with low dietary calcium intake (or individuals with very low intake), calcium supplementation may reduce the risk of hypertensive disorders of pregnancy.

  • Commonly cited WHO approach: elemental calcium 1.5–2.0 g/day in divided doses in settings of low intake (follow local guidance; consider kidney stone history and other risk factors).
  • Prioritize dietary sources when feasible; avoid excessive total daily intake.

Reference: WHO: Calcium supplementation during pregnancy

Diagnostic criteria

ACOG-aligned definitions for preeclampsia and HELLP syndrome (pregnancy or postpartum).
Preeclampsia — diagnostic criteria
New-onset hypertension after 20 weeks with proteinuria OR specific end-organ findings.
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Timing: Occurs after 20 weeks’ gestation or postpartum in a previously normotensive patient.

Blood pressure requirement

  • Systolic ≥140 mm Hg OR diastolic ≥90 mm Hg
  • On two occasions ≥4 hours apart (unless severe-range)

PLUS one of the following

Category Diagnostic threshold
Proteinuria ≥300 mg/24-hour urine
OR protein/creatinine ratio ≥0.3
OR dipstick ≥2+ (if quantitative methods unavailable)
Thrombocytopenia Platelets <100,000/µL
Renal insufficiency Serum creatinine >1.1 mg/dL
OR doubling of baseline creatinine in absence of other renal disease
Impaired liver function AST or ALT ≥2 × upper limit of normal
OR persistent RUQ / epigastric pain unresponsive to medication
Pulmonary edema Clinical or radiographic evidence
Neurologic symptoms New-onset headache unresponsive to medication
OR visual disturbances (scotomata, blurred vision, blindness)
Note: Proteinuria is not required if other severe features are present.

Reference: ACOG Practice Bulletin No. 222 (2020) Link

HELLP syndrome — diagnostic criteria
Hemolysis, Elevated Liver enzymes, Low Platelets; may occur with or without severe hypertension.
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Clinical pearl: HELLP may occur antepartum or postpartum and may present without classic severe-range BP.
Component Diagnostic findings
Hemolysis Abnormal peripheral smear (schistocytes)
OR LDH ≥600 IU/L
OR total bilirubin ≥1.2 mg/dL
Elevated liver enzymes AST or ALT ≥70 IU/L (≈ ≥2 × ULN)
Low platelets Platelets <100,000/µL
Classification systems (optional)
Used in some centers to stratify severity.
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  • Tennessee classification: All three components (H, EL, LP) present.
  • Mississippi classification:
    • Class I: Platelets <50,000/µL
    • Class II: Platelets 50,000–100,000/µL
    • Class III: Platelets 100,000–150,000/µL with other features
Management implication: HELLP syndrome is an indication for delivery after maternal stabilization, regardless of gestational age, in most cases.

References: ACOG PB 222; Sibai BM. HELLP syndrome. Obstet Gynecol.

Severe features & delivery timing

Criteria that drive escalation and delivery decisions (pregnancy or postpartum).
Severe features (preeclampsia with severe features)
Maternal end-organ findings and/or severe-range BP.
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Clinical point: Severe features increase stroke/hemorrhage and morbidity risk. Stabilize (BP, seizure prophylaxis when indicated), then determine delivery timing.
  • Severe-range BP: SBP ≥160 and/or DBP ≥110 that is persistent (especially if requiring urgent medication)
  • Neurologic symptoms: new-onset severe headache unresponsive to medication and not accounted for by alternative diagnoses; visual symptoms (scotomata, blurred vision, temporary blindness), altered mental status; seizure (eclampsia)
  • Pulmonary edema
  • Hepatic involvement: severe RUQ/epigastric pain, AST/ALT ≥2× ULN
  • Thrombocytopenia: platelets <100,000/µL
  • Renal insufficiency: creatinine >1.1 mg/dL OR doubling of baseline in absence of other renal disease

Reference: ACOG Practice Bulletin No. 222 (2020) Link

Delivery timing (practical guardrails)
Selected thresholds; individualize by maternal/fetal status and local pathway.
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  • Any gestational age: deliver for maternal/fetal deterioration that cannot be stabilized (e.g., refractory severe-range BP, eclampsia, pulmonary edema, abruption, progressive HELLP, worsening renal function, persistent severe symptoms, nonreassuring fetal status).
  • ≥34 weeks with severe features: delivery commonly recommended after maternal stabilization.
  • 37 weeks without severe features (gestational HTN / preeclampsia without severe features): delivery commonly recommended.
  • <34 weeks with severe features: selected stable patients may be candidates for expectant management in tertiary setting; deliver for any worsening criteria.
Bedside reminder: If you are repeatedly “re-treating” acute severe-range BP, reassess whether ongoing expectant management remains appropriate.

Reference: ACOG Practice Bulletin No. 222 (2020) Link

Magnesium sulfate — seizure prophylaxis / eclampsia treatment

Common regimens (IV infusion or IM), monitoring, renal impairment adjustments, and toxicity management.
Regimens & monitoring (with renal impairment notes)
Follow your institution’s protocol; adjust when renal clearance is reduced.
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Continuous IV infusion (typical)

4–6 g IV loading dose over ~15–20 minutes → 1–2 g/hour maintenance infusion. Many protocols continue for ~24 hours postpartum or after the last seizure.

Intermittent IM regimen (Pritchard-style, typical)

4 g IV (20% solution) ≤1 g/min → then 5 g IM (50% solution) in each buttock. Then 5 g IM q4h alternating sides (often with local anesthetic per protocol).

Continue magnesium ONLY if (bedside checks):
  • Respiratory rate adequate (commonly >12–16/min per protocol)
  • Urine output adequate (commonly >25–30 mL/hr)
  • Deep tendon reflexes present
Renal impairment / reduced clearance (ACOG PB 222 comment)
Magnesium is renally cleared. When renal function is reduced (e.g., elevated creatinine, oliguria), many protocols:
  • Give the usual loading dose (commonly 4–6 g IV), then use a lower maintenance rate (often 1 g/hr rather than 2 g/hr), OR hold maintenance if clinically indicated.
  • Check serum magnesium levels more frequently (often q4h) and titrate/hold for toxicity signs.
  • Hold magnesium for worsening oliguria, loss of reflexes, or respiratory depression; treat toxicity promptly.
ACOG Practice Bulletin No. 222 (2020): Gestational Hypertension and Preeclampsia
If eclampsia persists/recurs despite magnesium
Stepwise add-on anticonvulsants and “don’t-miss” differential when seizures continue.
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Immediate priorities
  • Call for help; protect airway/oxygenation; left lateral positioning when feasible.
  • Check BP and treat persistent severe-range hypertension per protocol (stroke prevention).
  • Assess for hypoglycemia, trauma, and alternative causes of seizure; obtain urgent consult as needed.
Step 1 If a seizure recurs while on magnesium: give an additional magnesium bolus 2 g IV over ~5 minutes (common toolkit recommendation).
Step 2 If seizures continue despite repeat magnesium bolus: consider alternative anticonvulsants (institution-specific sequence; involve anesthesia/ICU/neurology):
  • Lorazepam 4 mg IV over 3–5 minutes (onset 1-3 minutes). If seizure contiues or recurs after 10 to 15 minutes may give an additional 4 mg IV OR
  • Diazepam 5 to 10 mg IV slowly (onset 1-3 minutes). 5-10 mg IV slowly (can repeat every 15 minutes up to 30 mg)  OR
  • Midazolam  10 mg IM if no IV access (onset ~15 minutes)
  • If still seizing: move to longer-acting therapy (institution-specific; e.g., levetiracetam or fosphenytoin) and obtain consultation with neurology, anesthesia, or critical care.
  • Fosphenytoin 20 mg PE/kg IV @150mg/min (hospital protocols may require cardiac monitor)
  • Levetiracetam 60mg/kg IV (up to 4.5 g) at 100mg/min . Adjust for renal impairment
Persistent/refractory seizures Consider severe CNS events (e.g., intracranial hemorrhage, ischemic stroke, PRES) when seizures are persistent or recurrent — treat as high-acuity emergency and obtain urgent imaging/consultation per protocol.
When magnesium is contraindicated or unavailable
Key example: myasthenia gravis; consider non-magnesium anticonvulsants.
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Myasthenia gravis
Magnesium sulfate is contraindicated in myasthenia gravis (risk of worsening neuromuscular weakness/respiratory failure). Use alternative anticonvulsants and involve neurology/anesthesia early.
If magnesium is unavailable
In eclampsia, use alternative anti-seizure medications (e.g., levetiracetam, phenytoin) per protocol and consult neurology.
Note: For preeclampsia without severe features when magnesium is unavailable, some toolkits suggest observation alone unless clinically indicated.

Myasthenia case experience:Lake AJ et.al., used Levetiracetam 1 g intravenous bolus for seizure prophylaxis, then 500 mg intravenously every 12 hours until 2 days postpartum. Severe Preeclampsia in the Setting of Myasthenia Gravis (PMCID: PMC5322431)

Serum magnesium Clinical effect
> mmol/L mEq/L mg/dL
2–3.5 4–7 5–9 Therapeutic range (typical)
>3.5 >7 >9 Loss of reflexes (often begins)
>5 >10 >12 Respiratory paralysis risk
>12.5 >25 >30 Cardiac arrest risk
Toxicity management
Hold magnesium if reflexes are lost; treat respiratory depression promptly.
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  • If reflexes depressed but breathing normal → hold magnesium and check level (and renal function).
  • If respiratory depression: stop magnesium, support airway/oxygenation, and give calcium gluconate 10 mL of 10% IV over 10 minutes (typical rescue; confirm local supply/concentration).

Ensure continuous clinical monitoring per protocol; consult anesthesia/critical care for severe toxicity.

Treatment of acute severe-range hypertension (antepartum and postpartum)

Urgent treatment thresholds, immediate actions, and first-line pathways (OBRx / NPQIC framing).
Definition for urgent treatment: SBP ≥160 and/or DBP ≥110 that is persistent (commonly ≥15 minutes). Aim to initiate treatment within 30–60 minutes of confirmed severe-range BP to reduce maternal stroke risk.
Immediate actions (nursing + provider)
Confirm BP, assess symptoms, establish monitoring, and prepare first-line meds.
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  • Re-check BP promptly using appropriate cuff size; ensure proper technique and position.
  • Notify provider immediately for confirmed severe-range BP.
  • Assess symptoms: headache, visual changes, RUQ/epigastric pain, dyspnea/chest pain, neuro deficits.
  • Maternal monitoring: frequent BP (often q10 minutes during treatment), pulse oximetry as needed, I/O; consider continuous monitoring per acuity.
  • Fetal assessment as appropriate and per unit policy.
  • Establish IV access (if not already), draw labs per local “preeclampsia panel” as indicated.
  • Target: reduce BP below severe-range (commonly <160 systolic and <110 diastolic) while avoiding hypotension.
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OBRx linkChoose ONE first-line pathway based on IV access, contraindications, and local protocol. If BP remains severe-range after appropriate step dosing, obtain emergent consultation and transition to second-line/higher-acuity management as indicated.

Fluids

Judicious fluid administration is important in preeclampsia. Many protocols use fluid restriction (often ~80 mL/hour or ~1 mL/kg/hour) unless other clinical needs dictate.

Furosemide (Lasix)
Diuretic option when rapid diuresis is desired (e.g., acute pulmonary edema) — follow institutional protocol.
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Example IV dose: 20–40 mg IV over 1–2 minutes. If needed, repeat after ~2 hours or increase per response and protocol.

Contraindications
Anuria; known hypersensitivity to furosemide. Use caution with sulfonamide allergy history and monitor electrolytes/volume status.

Labeling (search): DailyMed: furosemide injection

References

Key guidance and practical pathways.
Guidelines & pathways
Aspirin prophylaxis, acute severe HTN, magnesium/management (ACOG PB 222), CMQCC escalation resources.
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  1. USPSTF (2021): Aspirin Use to Prevent Preeclampsia and Related Morbidity and Mortality: Preventive Medication. Link
  2. ACOG/SMFM Practice Advisory (Dec 2021): Low-Dose Aspirin Use for the Prevention of Preeclampsia and Related Morbidity and Mortality. Link
  3. ACOG Committee Opinion No. 743 (reaffirmed 2023): Low-Dose Aspirin Use During Pregnancy. Link
  4. NICE Guideline NG133: Hypertension in pregnancy — recommendations. Link
  5. NPQIC: Severe Intrapartum or Postpartum Hypertension — initial first-line management order set. PDF
  6. ACOG Practice Bulletin No. 222 (2020): Gestational Hypertension and Preeclampsia. Link
  7. Druzin M, Shields L, Peterson N, Sakowski C-ONQS, Cape V, Morton C. Improving Health Care Response to Hypertensive Disorders of Pregnancy, a California Maternal Quality Care Collaborative Quality Improvement Toolkit, 2021 p 132 PDF
  8. Lake AJ, Al Khabbaz A, Keeney R. Severe Preeclampsia in the Setting of Myasthenia Gravis. Case Rep Obstet Gynecol. 2017;2017:9204930. Link
  9. Perinatology OBRx: Magnesium sulfate (eclampsia/seizure prophylaxis). Link
  10. Perinatology OBRx: Antihypertensives (acute severe hypertension section). Link
  11. WHO eLENA: Calcium supplementation during pregnancy. Link
  12. DailyMed (NLM) for current manufacturer labeling/package inserts: DailyMed home
  13.  Kansas Perinatal Quality Collaborative Eclampsia Algorithm 2023 ACCESSED 1/3/2026

Page updated: 12/29/2025 (links accessed 12/29/2025).

Classic evidence base (selected)
Foundational magnesium sulfate evidence and classic references.
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  1. Which anticonvulsant for women with eclampsia? Evidence from the Collaborative Eclampsia Trial. Lancet. 1995;345:1455–1463.
  2. Duley L. Magnesium sulphate regimens for women with eclampsia: messages from the Collaborative Eclampsia Trial. Br J Obstet Gynaecol. 1996;103:103–105.
  3. Lu JF, Nightingale CH. Magnesium sulfate in eclampsia and pre-eclampsia: pharmacokinetic principles. Clin Pharmacokinet. 2000;38:305–314.
  4. Cunningham FG, et al. Hypertensive disorders. In: Williams Obstetrics. (edition varies).
Disclaimer: This content is for education and reference. It does not replace clinical judgment or local protocol. For emergencies, follow your institution’s severe hypertension / eclampsia pathway and obtain appropriate consultation.