7.2 Medical Complications of Pregnancy (Preeclampsia, Gestational Diabetes, Infections)

Medical Complications of Pregnancy

Medical conditions during pregnancy—whether unique to gestation or pre-existing—require vigilance to prevent maternal end-organ damage and adverse fetal outcomes. This section covers hypertensive disorders of pregnancy, gestational diabetes mellitus, and perinatal infections according to SOGC clinical practice guidelines.

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Hypertensive Disorders of Pregnancy (SOGC Classification)

Hypertension in pregnancy is defined as a systolic blood pressure (SBP) ≥140 mmHg and/or diastolic blood pressure (DBP) ≥90 mmHg based on the average of at least two measurements taken ≥15 minutes apart.

Classification Spectrum

1. Pre-existing (Chronic) Hypertension: Present prior to pregnancy or diagnosed before 20 weeks gestation.
2. Gestational Hypertension: New-onset hypertension arising after 20 weeks gestation without proteinuria or severe end-organ dysfunction.
3. Preeclampsia: New-onset hypertension arising after 20 weeks gestation accompanied by proteinuria OR one or more severe features / maternal end-organ dysfunction.
4. Pre-existing Hypertension with Superimposed Preeclampsia: Development of new proteinuria, sudden surge in blood pressure, or end-organ dysfunction in a patient with chronic hypertension.
5. Eclampsia: New-onset generalized tonic-clonic seizures in a patient with preeclampsia, not attributable to other neurological causes.
6. HELLP Syndrome: A severe variant of preeclampsia characterized by Hemolysis (microangiopathic hemolytic anemia with schistocytes, elevated LDH, low haptoglobin), Elevated Liver enzymes (AST/ALT >2x ULN), and Low Platelets (<100 × 10^9/L).

Diagnostic Criteria for Preeclampsia

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Management of Preeclampsia & Severe Hypertension

Antihypertensive Therapy

• Threshold for Treatment: SOGC guidelines mandate antihypertensive therapy for severe hypertension (SBP ≥160 or DBP ≥110 mmHg) to reduce maternal stroke risk. Target BP: SBP 130–145 / DBP 80–95 mmHg.
• First-Line Agents:
  • Oral Labetalol: Combined alpha/beta-blocker (100–400 mg PO BID/TID; IV boluses 20–80 mg for acute severe BP).
  • Oral Nifedipine XL: Long-acting calcium channel blocker (20–60 mg PO daily; rapid-acting oral nifedipine capsules 10 mg for acute control).
  • IV Hydralazine: Direct vasodilator (5–10 mg IV q20min).
  • Methyldopa: Central alpha-2 agonist (250–500 mg PO TID).

⚠️ EXAM TRAP: ACE inhibitors (e.g., enalapril), Angiotensin Receptor Blockers (ARBs, e.g., losartan), and Direct Renin Inhibitors are absolutely contraindicated in pregnancy due to severe fetal risks: renal dysgenesis, oligohydramnios, pulmonary hypoplasia, and skull hypocalcification.

Seizure Prophylaxis: Magnesium Sulfate

• Indication: Administered to patients with preeclampsia with severe features or eclampsia to prevent and treat tonic-clonic seizures.
• Dosing Protocol: Loading dose of 4–6 g IV over 15–20 minutes, followed by a continuous maintenance infusion of 1–2 g/hour IV for 24 hours postpartum.
• Monitoring for Toxicity:
  • Loss of deep tendon reflexes (patellar reflex): occurs at serum concentrations of 4–5 mmol/L (8–10 mEq/L).
  • Respiratory depression (<12 breaths/min): occurs at 6–7 mmol/L (12–15 mEq/L).
  • Cardiac arrest: occurs at >7.5 mmol/L (>15 mEq/L).
  • Renal monitoring: Urine output must exceed 30 mL/hour (magnesium is cleared renally).
• Antidote: Calcium Gluconate 1 g IV (10 mL of 10% solution IV over 3 minutes).

Prevention & Delivery Timing

• Low-Dose Aspirin Prophylaxis: High-risk patients (prior preeclampsia, chronic hypertension, pre-existing diabetes, multifetal gestation, autoimmune disease) should take low-dose aspirin (81–162 mg PO daily) starting between 12 and 16 weeks gestation until delivery.
• Delivery Timing:
  • Preeclampsia without severe features: Delivery at 37+0 weeks.
  • Preeclampsia with severe features: Delivery at 34+0 weeks (or earlier if maternal-fetal deterioration occurs).
  • Eclampsia, HELLP syndrome, unremitting severe hypertension, or fetal distress: Immediate delivery after maternal stabilization regardless of gestational age.

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Gestational Diabetes Mellitus (GDM)

Gestational Diabetes Mellitus is carbohydrate intolerance with onset or first recognition during pregnancy.

SOGC Screening Guidelines (24 to 28 Weeks Gestation)

SOGC endorses two acceptable screening strategies, with the 2-step approach preferred in most Canadian provinces:

Preferred 2-Step Approach:
Step 1: 50g Glucose Challenge Test (GCT) - Non-fasting
  ├─ <7.8 mmol/L  --> Normal (GDM Excluded)
  ├─ 7.8 - 11.0 mmol/L --> Proceed to Step 2 (75g OGTT)
  └─ ≥11.1 mmol/L --> Diagnostic of GDM (No 75g OGTT needed)

Step 2: Diagnostic 75g Oral Glucose Tolerance Test (OGTT) - Fasting
  GDM diagnosed if ANY 1 value is met or exceeded:
  ├─ Fasting: ≥5.3 mmol/L
  ├─ 1-Hour:  ≥10.6 mmol/L
  └─ 2-Hour:  ≥8.9 mmol/L

Alternative 1-Step Approach (75g OGTT fasting): GDM diagnosed if Fasting ≥5.1 mmol/L, 1-h ≥10.0 mmol/L, or 2-h ≥8.5 mmol/L.

Glycemic Targets & Management

• Target Glycemic Levels:
  • Fasting capillary glucose: <5.3 mmol/L
  • 1-hour postprandial: <7.8 mmol/L
  • 2-hour postprandial: <6.7 mmol/L
• First-Line Therapy: Nutritional counselling, low glycemic index diet, and moderate physical activity for 1–2 weeks.
• Pharmacotherapy: If >30% of blood glucose values exceed targets on lifestyle therapy:
  • Insulin is the gold-standard medical therapy (does not cross placenta; multiple daily injections or basal-bolus regimen).
  • Metformin is an acceptable second-line agent under SOGC guidelines if insulin is refused or unsafe.
• Postpartum Management: Discontinue insulin immediately after delivery. Perform a 75g OGTT at 6 to 12 weeks postpartum to screen for persistent Type 2 Diabetes.

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Perinatal Infections (TORCH Complex & Viral Hazards)

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SOGC Clinical Practice Pearls & Exam Traps

🩺 CLINICAL SCENARIO: A 32-year-old G2P1 at 32 weeks gestation presents with SBP 175/115 mmHg, hyperreflexia with 3 beats of clonus, and right upper quadrant tenderness. Laboratory evaluation reveals: Platelets 62 × 10^9/L, AST 260 U/L, ALT 240 U/L, total bilirubin 38 µmol/L, and LDH 950 U/L. What is the diagnosis and immediate management plan?

• Diagnosis: HELLP Syndrome (severe form of preeclampsia).
• Management:
  1. Administer IV Magnesium Sulfate (4 g IV load, 1–2 g/h maintenance) for eclampsia prophylaxis.
  2. Administer IV Labetalol or rapid-acting oral Nifedipine for acute blood pressure reduction.
  3. Administer antenatal corticosteroids (Betamethasone 12 mg IM q24h × 2 doses) for fetal lung maturity.
  4. Proceed with urgent stabilization and delivery (HELLP is an absolute indication for prompt delivery).