old guidelines for gestational htn and preeclampsia
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Gestational Hypertension & Preeclampsia: Guidelines
(Based primarily on ACOG criteria as presented in Creasy & Resnik's Maternal-Fetal Medicine and Harrison's Principles of Internal Medicine)
Classification of Hypertensive Disorders of Pregnancy
There are four distinct types:
- Chronic hypertension
- Preeclampsia and eclampsia
- Gestational hypertension
- Preeclampsia superimposed on chronic hypertension
1. Gestational Hypertension
Definition: New-onset blood pressure elevations after 20 weeks' gestation in the absence of proteinuria.
- Threshold: BP ≥ 140/90 mmHg on two measurements ≥ 4 hours apart
- This is a provisional diagnosis - it includes women who will later develop preeclampsia but have not yet shown proteinuria
- Must be monitored closely for progression to preeclampsia
- If BP does not normalize within 6 weeks postpartum, the diagnosis is revised to chronic hypertension
- Gestational hypertension progresses to overt preeclampsia in 10-25% of cases
- Severe gestational hypertension carries similar risks for adverse outcomes as preeclampsia, even without proteinuria
"Gestational hypertension with severe features of the disease is best classified as preeclampsia." - Harrison's Principles of Internal Medicine 22E
2. Preeclampsia
Definition: New-onset hypertension after 20 weeks + proteinuria OR end-organ damage markers.
Diagnostic Criteria
Hypertension:
- Systolic BP ≥ 140 mmHg OR diastolic BP ≥ 90 mmHg
- On two occasions at least 4 hours apart
- Note: The old criterion of a rise of 30 mmHg systolic or 15 mmHg diastolic above baseline is no longer used - it was removed because there is no increased risk of adverse outcomes in this group alone
Proteinuria (any one of):
- ≥ 300 mg protein on 24-hour urine (preferred method)
- Protein-to-creatinine ratio ≥ 0.3 (mg/dL)
- Dipstick 2+ (only when quantitative methods unavailable - unreliable due to false positives/negatives)
Preeclampsia without proteinuria can be diagnosed when hypertension is accompanied by ANY of:
- Thrombocytopenia (platelets < 100,000/µL)
- Elevated liver enzymes (transaminases > 2× upper limit of normal)
- New-onset renal insufficiency (serum creatinine > 1.1 mg/dL, in absence of other renal disease)
- Pulmonary edema
- New-onset cerebral or visual disturbances
Severity Classification
ACOG recommends abandoning the term "mild" - preeclampsia always carries significant morbidity/mortality risk.
| Feature | Without Severe Features | With Severe Features |
|---|---|---|
| BP | ≥140/90 mmHg | ≥160/110 mmHg (on 2 occasions, ≥4 hrs apart) |
| Neurologic | None | New-onset headache unresponsive to meds, visual disturbances |
| Hepatic | None | Persistent RUQ/epigastric pain unresponsive to meds; transaminases > 2× normal |
| Platelets | Normal | < 100,000/µL |
| Renal | None | Creatinine > 1.1 mg/dL |
| Pulmonary | None | Pulmonary edema |
| Fetal | None | IUGR (in some classifications) |
3. Eclampsia
- Definition: Generalized (tonic-clonic) seizures in a patient with preeclampsia
- In the absence of treatment, ~1 in 100 cases of preeclampsia progress to eclampsia
4. HELLP Syndrome
A special subtype of preeclampsia with severe features:
- H - Hemolysis
- EL - Elevated liver enzymes
- LP - Low platelets
HELLP is a major cause of maternal morbidity and mortality. Additional complications include coagulopathy/DIC, CVA, hepatic capsule rupture, and placental abruption.
Risk Factors for Preeclampsia
| Risk Factor | Notes |
|---|---|
| Nulliparity | Largest population-attributable fraction (~32%) |
| Prior preeclampsia | Strong predictor |
| Chronic hypertension | 25% will develop superimposed preeclampsia |
| Diabetes mellitus | ~20% overall risk; up to 70% with classes F/R |
| Chronic renal disease | Significant risk factor |
| Antiphospholipid syndrome | Strong independent risk factor |
| SLE | Especially with HTN or lupus nephropathy |
| Obesity | ~3× increased risk |
| Advanced maternal age | Risk independent of parity |
| African-American race | More related to disease severity than incidence |
| Multiple gestation | Increased risk |
| IVF pregnancy | Increased risk |
| Family history | First-degree relative with preeclampsia |
Pathophysiology (Key Points)
- Chronic uteroplacental ischemia - failure of physiologic transformation of spiral arteries
- Exaggerated maternal inflammatory response
- Imbalance of angiogenic factors: excess sFlt-1 (anti-angiogenic) + decreased PlGF (pro-angiogenic)
- sFlt-1/PlGF ratio ≥ 40 is associated with increased risk of developing severe disease within 2 weeks
- Loss of cerebral vascular autoregulation explains neurologic manifestations and stroke risk
- Glomerular endotheliosis is the pathognomonic renal lesion (swollen endothelial cells nearly occluding capillary lumen)
- Posterior Reversible Encephalopathy Syndrome (PRES) - vasogenic parietooccipital edema seen on CT/MRI in severe disease
Management Principles
Definitive Treatment
Delivery is the only cure. Timing depends on severity and gestational age.
Antihypertensive Therapy
- Indication: BP ≥ 160/110 mmHg (severe range) - treat urgently to prevent maternal stroke
- Modest BP reduction to prevent stroke while maintaining uteroplacental perfusion
- Agents used: labetalol, hydralazine (IV), nifedipine (oral)
Seizure Prophylaxis
- Magnesium sulfate is the agent of choice for prevention and treatment of eclamptic seizures
Aspirin Prophylaxis
- Low-dose aspirin initiated between 12 and 14 weeks of gestation reduces the risk of preeclampsia in high-risk women
Preeclampsia Without Severe Features
- Close outpatient or inpatient surveillance
- Delivery typically at ≥ 37 weeks
Preeclampsia With Severe Features
- Delivery if ≥ 34 weeks
- Corticosteroids for fetal lung maturity if 24-34 weeks
- Intensive maternal monitoring regardless of gestational age
Key Differentiator: Chronic Hypertension vs Gestational HTN
| Feature | Chronic HTN | Gestational HTN | Preeclampsia |
|---|---|---|---|
| Onset | < 20 weeks (or pre-existing) | ≥ 20 weeks | ≥ 20 weeks |
| Proteinuria | Usually absent | Absent | Present OR end-organ damage |
| Postpartum resolution | Persists > 6 weeks | Resolves < 6 weeks | Resolves postpartum |
Sources:
- Creasy & Resnik's Maternal-Fetal Medicine: Principles and Practice, Ch. 45 (pp. 1055-1140)
- Harrison's Principles of Internal Medicine 22E (2025), Ch. on Medical Disorders of Pregnancy
- Goldman-Cecil Medicine, Hypertensive Disorders Unique to Pregnancy
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