Pre-eclampsia: Essential Information for NAC OSCE Canada
Definition and Diagnosis
Pre-eclampsia is defined as new-onset hypertension (BP ≥140/90 mmHg) occurring after 20 weeks of gestation, combined with either proteinuria (≥0.3g/24h or protein:creatinine ratio ≥30mg/mmol) OR evidence of maternal organ dysfunction OR uteroplacental dysfunction 1, 2.
Key Diagnostic Criteria (ISSHP Definition)
You need hypertension PLUS at least one of:
- Proteinuria (≥300mg/24h, ≥30mg/mol protein:creatinine, or ≥2+ dipstick)
- Renal dysfunction (creatinine ≥90μmol/L)
- Liver involvement (ALT or AST >40 IU/L, with or without RUQ/epigastric pain)
- Neurological complications (eclampsia, altered mental status, stroke, severe headaches, visual scotomata, clonus)
- Hematological complications (platelets <150,000/μL, DIC, hemolysis)
- Uteroplacental dysfunction (fetal growth restriction, abnormal umbilical artery Doppler, stillbirth) 2
Classification
Preterm pre-eclampsia (delivery <37 weeks) versus term pre-eclampsia (delivery ≥37 weeks) 2. Early-onset disease (<34 weeks) carries significantly higher maternal and perinatal morbidity and mortality 3, 2.
Epidemiology and Impact
- Affects 3-5% of pregnancies 4
- Second leading cause of maternal mortality worldwide 1
- Causes 76,000 maternal deaths and 500,000 fetal/neonatal deaths annually 2
- Women in low-resource countries face disproportionately higher risk 2
- Black women experience higher morbidity and mortality than White women, attributed to systemic racism, chronic stress, and healthcare inequities 5
Risk Factors to Identify
High-Risk Factors
- Previous pre-eclampsia
- Chronic hypertension
- Pre-existing diabetes (Type 1 or 2)
- Renal disease
- Autoimmune disease (SLE, antiphospholipid syndrome)
- Multiple pregnancy 2
Moderate-Risk Factors
- Nulliparity
- Advanced maternal age (≥40 years)
- Obesity (BMI ≥35)
- Family history of pre-eclampsia
- Afro-Caribbean or South Asian ethnicity
- Short or long interpregnancy interval
- Assisted reproductive technology 2
Emerging Risk Factors
- Mental health disorders (15% with probable depression, 23% with PTSD symptoms in affected women) 5
- Sleep-disordered breathing (doubles risk when present in early/mid-pregnancy, aOR ~1.95) 5
Screening Approach
All pregnant women should be screened with blood pressure measurements throughout pregnancy 1. This is a B recommendation from USPSTF with adequate evidence that screening combined with treatment substantially reduces maternal and perinatal morbidity and mortality 1.
First-Trimester Combined Screening (11-14 weeks)
The optimal approach combines:
- Maternal risk factors
- Mean arterial pressure (MAP)
- Serum placental growth factor (PlGF)
- Uterine artery pulsatility index (UTPI)
- Can add PAPP-A if already measuring for aneuploidy screening 2
High risk is defined as ≥1 in 100 risk based on this combined screening 2. Where resources are limited, screen all women with maternal factors + MAP, then reserve PlGF and UTPI for the high-risk subset 2.
Prevention
Aspirin Prophylaxis
For women identified as high-risk in first trimester, prescribe aspirin 100-160mg (ideally ~150mg) daily at bedtime, starting at 11-14 weeks (before 16 weeks, not after 20 weeks) and continuing until 36 weeks of gestation 2, 6. This is the most evidence-based preventive intervention 2.
Do NOT prescribe low-dose aspirin to all pregnant women 2.
Calcium Supplementation
In women with low dietary calcium intake (<800mg/day), provide either calcium replacement (≤1g elemental calcium/day) or supplementation (1.5-2g elemental calcium/day) to reduce both early and late-onset pre-eclampsia 2.
Lifestyle Measures
Encourage physical activity during pregnancy (≥140 minutes per week) to reduce risk of gestational hypertension and pre-eclampsia 6, 7.
Management During Pregnancy
Non-Severe Pre-eclampsia
- Initiate oral antihypertensive therapy when BP is 140-159/90-109 mmHg 6
- Between 34-36+6 weeks: Do NOT routinely induce delivery; expectant management is preferred as immediate delivery increases moderate prematurity without clear maternal benefit 6
- At 37-41 weeks: Induce labor to reduce maternal morbidity; attempt vaginal delivery unless contraindicated 6
Severe Pre-eclampsia
Current management targets maternal hypertension and seizure prevention with:
- Antihypertensives (hydralazine, labetalol) 8
- Magnesium sulfate for seizure prophylaxis 8
- Delivery is the only definitive cure 3, 8
Long-Term Implications
For Mother
- 75% increased risk of cardiovascular-related mortality compared to women without pre-eclampsia 5
- Life expectancy reduced by 10 years on average for women with preterm pre-eclampsia 2
- Increased future risk of chronic hypertension, stroke, renal impairment, metabolic syndrome, and diabetes 2
- Women with history of pre-eclampsia require lifelong cardiovascular risk monitoring and blood pressure surveillance 6
For Offspring
In utero exposure associated with:
- Increased blood pressure and BMI
- Neurodevelopmental disorders
- Insulin resistance, diabetes, coronary artery disease, and hypertension in later life 5, 2
Common Pitfalls to Avoid
- Do NOT rely solely on maternal risk factors for screening—this approach is inadequate 2
- Do NOT use biomarkers like PlGF or sFlt-1/PlGF ratio routinely for diagnosis or management decisions—insufficient evidence they reduce morbidity 6
- Do NOT screen for maternal thrombophilia in women with history of pre-eclampsia—not recommended 6
- Do NOT assume pre-eclampsia ends with delivery—it's a systemic disease with lifelong cardiovascular implications 9