Treatment of Preeclampsia

Preeclampsia is a hypertensive disorder of pregnancy that is definitively cured only by delivery. All other interventions are temporizing measures aimed at protecting the mother and fetus until delivery is feasible.

1. Definitive Treatment: Delivery

<24 weeks: Perinatal mortality is >80%; termination is usually recommended.
24–37 weeks: Balance neonatal benefit of prolonging pregnancy against maternal risk. Expectant management (postponing delivery 1–2 weeks with intensive monitoring) has been shown in RCTs to reduce neonatal complications in severe cases at 28–32 weeks, without significantly increasing maternal complications.
>37 weeks: Immediate delivery is almost always indicated — minimal fetal benefit in prolonging pregnancy.

Indications for expedient delivery regardless of gestational age:

Non-reassuring fetal testing
Suspected placental abruption
Thrombocytopenia
Worsening liver or renal function
HELLP syndrome
Unrelenting headache, visual changes, epigastric pain, nausea/vomiting

Mode of delivery (induction vs. cesarean) shows similar maternal and neonatal outcomes in retrospective studies.

2. Blood Pressure Management

The goal is not to minimize long-term cardiovascular risk (as in non-pregnant adults), but to prevent acute maternal complications (especially cerebral hemorrhage) while maintaining uteroplacental perfusion.

Threshold for treatment: BP ≥150–160 mmHg systolic or ≥100–110 mmHg diastolic. Aggressive lowering below this threshold risks fetal distress from reduced placental perfusion.
The CHIPS trial (2015, n=987) showed that targeting a diastolic BP of 85 mmHg (tight control) is safe for the fetus and reduces maternal complications (severe hypertension, thrombocytopenia, transaminitis) compared to targeting 100 mmHg.

Oral Antihypertensive Agents

Drug	Notes
Methyldopa	First-line oral agent; most safety data; centrally acting α2-agonist; drawbacks: short half-life, sedation
Labetalol	α/β-blocker; preserves uteroplacental flow; used orally and IV; widely preferred
Nifedipine (long-acting)	Calcium channel blocker; safe and effective; growing experience
Clonidine	Comparable to methyldopa; fewer data
Atenolol	Avoid — associated with fetal growth restriction
ACE inhibitors / ARBs	Contraindicated in 2nd and 3rd trimester — cause renal dysgenesis, oligohydramnios, pulmonary hypoplasia, IUGR
Diuretics	Not first-line (theoretical concern about volume depletion); appropriate if pulmonary edema develops

IV Agents for Severe/Urgent Hypertension

Labetalol IV: 5–10 mg boluses; safe and effective; short acting
Hydralazine IV: 5 mg boluses; long-used; no adverse fetal effects documented
Nicardipine IV: Safe; used for tocolysis and hypertension; good option
Short-acting nifedipine oral: Controversial in non-pregnant patients, but a meta-analysis supports safe use in pregnancy for severe hypertension — useful where IV access is unavailable

(Nitroprusside is generally avoided due to risk of fetal cyanide toxicity.)

3. Magnesium Sulfate — Seizure Prophylaxis

Magnesium sulfate is the drug of choice for prevention and treatment of eclamptic seizures, not as an antihypertensive.

Regimen: 4–6 g IV loading dose over 20–30 minutes, followed by 1–2 g/hr continuous infusion for ≥24 hours
Superior to diazepam and phenytoin (proven in RCTs)
The Magpie Trial (>10,000 women, 33 countries) showed magnesium reduced eclamptic seizures by 50% (0.8% vs 1.9%) vs placebo
Reduce dose in renal insufficiency (2 g IV bolus, then check serum levels before increasing)

Monitoring for toxicity:

Magnesium Level	Effect
Therapeutic	Loss of deep tendon reflexes (patellar)
Toxic	Respiratory depression, flaccid paralysis, cardiac arrest
Antidote	Calcium gluconate 1 g IV

4. Management of HELLP Syndrome

HELLP (Hemolysis, Elevated Liver enzymes, Low Platelets) is managed similarly to severe preeclampsia:

IV magnesium sulfate
Blood pressure control
Correct coagulopathy as indicated
Definitive treatment: delivery, especially ≥34 weeks
Corticosteroids (e.g., betamethasone) can delay delivery and improve fetal lung maturity at <34 weeks

5. Postpartum Considerations

Magnesium infusion is continued for ≥24 hours postpartum
Blood pressure can worsen in the first few days postpartum — continue antihypertensive therapy
Preeclampsia can develop up to 4 weeks postpartum — postpartum surveillance is essential

Summary Algorithm

Preeclampsia diagnosed
        ↓
≥37 weeks? → Deliver
        ↓
<37 weeks with severe features?
        ↓
YES → Stabilize: MgSO₄ + antihypertensives → Deliver
NO (mild, 34–37 wks) → Expectant management with close monitoring → Deliver at 37 wks
<34 weeks → Intensive monitoring ± corticosteroids → Deliver if severe features develop

Sources: Brenner and Rector's The Kidney, 2-Volume Set · Tintinalli's Emergency Medicine · Goldman-Cecil Medicine · Morgan and Mikhail's Clinical Anesthesiology, 7e · Creasy & Resnik's Maternal-Fetal Medicine

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