How is pre-eclampsia diagnosed and managed in pregnant women?

Diagnosis and Management of Pre-eclampsia

Diagnostic Criteria

Pre-eclampsia is diagnosed by new-onset hypertension (≥140/90 mmHg) after 20 weeks' gestation, and proteinuria is no longer mandatory for diagnosis. 1

• Hypertension is confirmed when blood pressure is ≥140 mmHg systolic or ≥90 mmHg diastolic on two occasions 2
• When proteinuria is present, it is confirmed by:
  • Spot urine protein/creatinine ratio ≥30 mg/mmol (or 0.3 mg/mg) 2, 1
  • ≥300 mg protein in 24-hour urine collection 2
  • ≥1+ on dipstick testing 1
• In the absence of proteinuria, diagnosis requires evidence of maternal organ dysfunction or uteroplacental dysfunction 3

Severity Assessment: Identify Severe Features Immediately

All cases of pre-eclampsia should be treated as potentially severe, as rapid progression to life-threatening complications can occur even with initially mild presentations. 1, 4

Severe features requiring urgent intervention include:

• Severe hypertension: BP ≥160/110 mmHg on two occasions at least 15 minutes apart 1
• Thrombocytopenia: Platelets <100,000/μL 1
• Renal dysfunction: Creatinine >1.1 mg/dL or doubling of baseline 1
• Liver dysfunction: Elevated liver enzymes (AST/ALT ≥2× upper limit of normal) 1
• Pulmonary edema 1, 4
• Neurological symptoms: Severe headache, visual disturbances (scotomata, cortical blindness), hyperreflexia with clonus 2, 1
• Right upper quadrant or epigastric pain (indicating liver capsule distension or hepatic hemorrhage) 2

Immediate Stabilization for Severe Hypertension

Urgent antihypertensive therapy must be initiated immediately when BP ≥160/110 mmHg persists for >15 minutes to prevent maternal cerebral hemorrhage. 1

First-line IV antihypertensive options:

• IV labetalol: 20 mg IV bolus, then 40 mg after 10 minutes, then 80 mg every 10 minutes (maximum cumulative dose 220 mg) 1
• IV hydralazine: 5-10 mg IV every 20 minutes as needed 1
• Oral nifedipine may be used as an alternative in monitored settings 5, 4

Target blood pressure:

• Systolic 110-140 mmHg and diastolic 85 mmHg (or at minimum <160/105 mmHg) 1, 5, 4

For non-severe hypertension (140-159/90-109 mmHg):

• Oral agents include methyldopa, labetalol, oxprenolol, and nifedipine 4
• Second or third-line agents include hydralazine and prazosin 4

Seizure Prophylaxis with Magnesium Sulfate

Magnesium sulfate must be administered immediately to all patients with severe pre-eclampsia or those with proteinuria plus severe hypertension or any neurological symptoms. 1, 4

• Loading dose: 4-5 g IV over 5 minutes (diluted in 250 mL of 5% dextrose or 0.9% normal saline) 1, 6
• Maintenance: 1-2 g/hour continuous IV infusion 1, 6
• Magnesium prevents seizures by blocking neuromuscular transmission and decreasing acetylcholine release at the motor end-plate 6
• Effective anticonvulsant serum levels range from 2.5 to 7.5 mEq/L 6
• Monitor deep tendon reflexes (disappear at plasma levels approaching 10 mEq/L) and respiratory function 6
• Critical warning: Continuous maternal administration beyond 5-7 days can cause fetal abnormalities 6

Comprehensive Laboratory and Fetal Assessment

Initial laboratory workup:

• Complete blood count with focus on hemoglobin and platelet count 1, 4
• Comprehensive metabolic panel: Liver transaminases (AST/ALT), creatinine, uric acid 1, 4
• Spot urine protein/creatinine ratio 1, 4

Ongoing monitoring:

• Laboratory tests should be repeated at least twice weekly in women with pre-eclampsia 1, 4
• Blood pressure monitoring at least twice weekly or continuously if severe features are present 4

Fetal assessment:

• Initial ultrasound to assess fetal biometry, amniotic fluid volume, and umbilical artery Doppler 2, 4
• Continuous electronic fetal monitoring to assess fetal heart rate and variability 5, 4
• Serial evaluation of fetal growth, amniotic fluid volume, and umbilical artery Doppler from 24 weeks' gestation until birth, with fetal growth evaluated no more frequently than at 2-week intervals 2

Delivery Timing: Gestational Age-Based Algorithm

Immediate delivery is indicated after maternal stabilization at ≥37 weeks' gestation. 1, 5, 4

At 34-37 weeks' gestation:

• Without severe features: Expectant management with close monitoring is appropriate 1
• With severe features: Deliver after maternal stabilization 1

Before 34 weeks' gestation:

• Expectant management is possible in select women with severe pre-eclampsia before 32 weeks' gestation 7
• Administer corticosteroids between 24-34 weeks' gestation to reduce neonatal mortality and morbidity 7

Absolute Indications for Immediate Delivery (Any Gestational Age)

Deliver immediately regardless of gestational age if any of the following develop: 1, 4

• Inability to control BP despite ≥3 classes of antihypertensives in appropriate doses 1
• Placental abruption 1
• Non-reassuring fetal status on continuous monitoring 1, 5
• Maternal oxygen saturation deterioration (<90%) 1
• Pulmonary edema 1, 4
• Progressive thrombocytopenia (declining platelet counts on serial measurements) 1
• Progressively abnormal liver or renal function tests (worsening trends, not static elevations) 1
• Abnormal neurological features: severe intractable headache, repeated visual scotomata, or eclamptic seizures 1

HELLP Syndrome: Special Considerations

HELLP syndrome (hemolysis, elevated liver enzymes, low platelets) is part of the pre-eclampsia spectrum and should be managed as severe pre-eclampsia. 1

• Maternal mortality rate is 3.4% in HELLP syndrome 1
• Epigastric or right upper quadrant pain is a hallmark symptom 1
• Monitor glucose intraoperatively as severe hypoglycemia can occur 1
• Delivery is the definitive treatment 8

Management of Pulmonary Edema

• Drug of choice: IV nitroglycerin (glyceryl trinitrate) starting at 5 mcg/min, gradually increased every 3-5 minutes to maximum 100 mcg/min 1
• Plasma volume expansion is NOT recommended routinely 1, 4

Setting of Care

Women with pre-eclampsia should be assessed in hospital when first diagnosed, and those with severe features should be managed in facilities with appropriate obstetrical care, maternal intensive care capabilities, and NICU for premature infants. 4

Critical Pitfalls to Avoid

• Do not underestimate disease severity based on "mild" classification—all pre-eclampsia can rapidly progress to emergencies 1, 5, 4
• Blood pressure alone is not a reliable indicator of disease severity—serious organ dysfunction can develop at relatively mild levels of hypertension 1, 4
• Do not use serum uric acid or level of proteinuria as indication for delivery 1, 4
• Do not delay delivery at ≥37 weeks based on non-reactive NST—delivery is indicated regardless of fetal testing results 1, 5
• Do not reduce antihypertensives if diastolic BP falls <80 mmHg 1
• Do not use diuretics routinely—they further reduce plasma volume which is already contracted in pre-eclampsia 1

Postpartum Management

• Monitor BP and clinical condition at least every 4 hours while awake 1
• Continue antihypertensives administered antenatally 1
• Avoid NSAIDs for postpartum analgesia unless other analgesics are not working, especially if renal disease or placental abruption are present 1
• Continue magnesium sulfate for at least 24 hours postpartum in women with severe disease 7

Follow-Up and Long-Term Cardiovascular Risk

Review all women at 3 months postpartum to ensure BP, urinalysis, and laboratory abnormalities have normalized. 1

• Women with pre-eclampsia have significantly increased long-term cardiovascular risks including hypertension, ischemic heart disease, stroke, and heart failure 9, 3, 10
• Annual medical review is required lifelong 1
• Early-onset pre-eclampsia contributes the greatest long-term cardiovascular risk 10
• Women who survive pre-eclampsia have reduced life expectancy with increased risks of stroke, cardiovascular disease, and diabetes 3

Prevention Strategies

For women at increased risk, the following preventive measures should be implemented:

• Low-dose aspirin (preferably 150 mg/day) started before 16 weeks of pregnancy 2
• Calcium supplementation (1.2-2.5 g/day) in women with low calcium intake (<600 mg/day) 2
• Exercise at least 3 days per week for an average of 50 minutes using a combination of aerobic exercise, strength, and flexibility training 2