Medical Complications of Pregnancy: Preeclampsia, Gestational Diabetes, and Thyroid Disease

Preeclampsia is a multisystem disorder of pregnancy characterized by new-onset hypertension (≥140/90 mmHg) after 20 weeks of gestation, accompanied by proteinuria or other maternal organ dysfunction. This condition affects 2-8% of pregnancies worldwide and remains a leading cause of maternal and perinatal morbidity and mortality.

Pathophysiology: The disorder begins with abnormal placentation in the first trimester, leading to inadequate trophoblast invasion and spiral artery remodeling. This results in placental hypoxia and the release of anti-angiogenic factors including soluble fms-like tyrosine kinase-1 (sFlt-1) and soluble endoglin (sEng), which antagonize pro-angiogenic factors like vascular endothelial growth factor (VEGF) and placental growth factor (PlGF).

⚡ HIGH-YIELD: Diagnostic Criteria (ACOG 2019)

*Can diagnose preeclampsia without proteinuria if hypertension plus any severe feature present.

Severe Features Include:

• SBP ≥160 mmHg or DBP ≥110 mmHg
• Platelet count <100,000/μL (100 × 10⁹/L)
• Serum creatinine >97.2 μmol/L (1.1 mg/dL) or doubling of baseline
• ALT or AST >2× upper normal limit
• Persistent epigastric or right upper quadrant pain
• Pulmonary edema
• New-onset cerebral or visual disturbances

🔬 Risk Factors:

• Nulliparity
• Previous preeclampsia
• Chronic hypertension
• Diabetes mellitus
• Renal disease
• Autoimmune disorders
• Multiple gestation
• Advanced maternal age (>40 years)
• Obesity (BMI >30 kg/m²)

Management of preeclampsia requires careful monitoring and timely intervention to prevent progression to eclampsia or other severe complications. The only definitive treatment is delivery, but timing must balance maternal safety with fetal maturity.

Prevention Strategies: ⚠️ PEARL: Low-dose aspirin (81 mg daily) should be initiated between 12-28 weeks (ideally before 16 weeks) for high-risk patients and continued until delivery.

High-risk criteria for aspirin prophylaxis:

• Previous preeclampsia
• Multifetal gestation
• Chronic hypertension
• Type 1 or 2 diabetes
• Renal disease
• Autoimmune disease

Moderate-risk factors (≥2 required for aspirin):

• Nulliparity
• Obesity (BMI >30)
• Family history of preeclampsia
• Age >35 years
• Personal history factors

Acute Management Algorithm:

Preeclampsia Diagnosis ↓ Assess for severe features ↓ ┌─────────┴─────────┐ ↓ ↓ No severe features Severe features ↓ ↓ ≥37 weeks: Deliver <34 weeks: Consider expectant <37 weeks: Monitor management with close monitoring 34-37 weeks: Individualize ≥37 weeks: Deliver promptly

Antihypertensive Management:

• First-line: Labetalol 20 mg IV, then 40-80 mg every 10 minutes (max 300 mg)
• Second-line: Hydralazine 5-10 mg IV every 15-20 minutes
• Third-line: Nifedipine immediate-release 10-20 mg PO

Target BP: 140-150/90-100 mmHg (avoid excessive reduction)

Magnesium Sulfate for Seizure Prophylaxis:

• Loading dose: 4-6 g IV over 15-20 minutes
• Maintenance: 1-2 g/hour IV infusion
• Monitor: Reflexes, respirations, urine output
• Antidote: Calcium gluconate 1 g IV

Corticosteroids: Betamethasone 12 mg IM every 24 hours × 2 doses for fetal lung maturity if delivery anticipated within 7 days (24-34 weeks gestation).

Gestational diabetes mellitus (GDM) is glucose intolerance with onset or first recognition during pregnancy. It affects approximately 6-15% of pregnancies and significantly increases risks for both maternal and fetal complications.

Pathophysiology: Pregnancy induces insulin resistance through placental hormones (human placental lactogen, cortisol, prolactin). In women with inadequate beta-cell compensation, hyperglycemia develops, typically in the second or third trimester.

⚡ HIGH-YIELD: Screening and Diagnostic Criteria

Two-Step Approach (Carpenter-Coustan Criteria):

Step 1: 50g Glucose Challenge Test (24-28 weeks)

• 1-hour glucose ≥140 mg/dL (7.8 mmol/L): Proceed to Step 2
• Alternative cutoff ≥130 mg/dL (7.2 mmol/L) for higher sensitivity

Step 2: 100g Oral Glucose Tolerance Test (3-hour)

Diagnosis requires ≥2 abnormal values

One-Step Approach (IADPSG Criteria): 75g OGTT at 24-28 weeks (fasting required)

Diagnosis requires ≥1 abnormal value

🔬 Risk Factors for GDM:

• Previous GDM
• BMI ≥25 kg/m² (≥23 kg/m² for Asian women)
• First-degree relative with diabetes
• Previous macrosomic infant (>4000g)
• Polycystic ovary syndrome
• Age ≥25 years
• High-risk ethnicity (Hispanic, African American, Native American, South Asian, Pacific Islander)

Early Screening Indications: Screen at first prenatal visit if:

• Previous GDM
• Marked obesity (BMI ≥35)
• Strong family history of diabetes
• Previous unexplained fetal demise

Complications: Maternal: Preeclampsia, cesarean delivery, future Type 2 diabetes Fetal: Macrosomia, birth trauma, neonatal hypoglycemia, respiratory distress syndrome, future obesity/diabetes

Management of GDM focuses on maintaining euglycemia to reduce maternal and fetal complications. Treatment involves lifestyle modifications, glucose monitoring, and pharmacotherapy when indicated.

Glycemic Targets:

Initial Management - Medical Nutrition Therapy:

• Caloric intake: 30-35 kcal/kg/day for normal BMI, 25 kcal/kg/day for overweight, 12-14 kcal/kg/day for obese
• Carbohydrate distribution: 40-50% of total calories
  • Breakfast: 15-30g carbohydrates (morning insulin resistance)
  • Lunch/Dinner: 30-45g carbohydrates each
  • Snacks: 15-30g carbohydrates

Exercise Recommendations:

• Moderate exercise 30 minutes most days
• Postprandial walking particularly effective
• Contraindicated if obstetric complications present

⚠️ PEARL: Start pharmacotherapy if >20% of glucose values exceed targets after 1-2 weeks of lifestyle modification.

Pharmacologic Management:

First-line: Insulin

• Rapid-acting: Lispro, Aspart (FDA Pregnancy Category B)
• Intermediate-acting: NPH insulin
• Long-acting: Avoid glargine/detemir (limited data)

Typical insulin regimen:

Starting dose: 0.7-1.0 units/kg/day

• 2/3 in AM (2/3 NPH + 1/3 rapid-acting)
• 1/3 in PM (1/2 NPH at bedtime + 1/2 rapid-acting at dinner)

Adjust based on glucose patterns:

• High fasting: ↑ evening NPH
• High postprandial: ↑ rapid-acting before meals

Second-line: Metformin

• Starting dose: 500 mg twice daily
• Maximum: 2000-2500 mg daily
• Crosses placenta but appears safe
• 25% require additional insulin

Second-line: Glyburide

• Starting dose: 2.5 mg daily
• Maximum: 20 mg daily in divided doses
• Does not cross placenta significantly
• Increased neonatal hypoglycemia risk

Monitoring:

• Self-monitoring blood glucose 4× daily
• Fetal surveillance: Serial ultrasounds for growth, antepartum testing if complications
• Delivery timing: 39-40 weeks for well-controlled GDM, earlier if complications

Postpartum Management:

• Discontinue all diabetes medications
• Screen at 6-12 weeks postpartum with 75g OGTT
• Annual diabetes screening thereafter
• Preconception counseling for future pregnancies

Thyroid disorders are among the most common endocrine conditions in pregnancy, affecting 2-17% of pregnancies. Maternal thyroid hormones are crucial for fetal neurodevelopment, particularly in the first trimester before fetal thyroid function begins.

Physiological Changes in Pregnancy:

• ↑ Thyroid-binding globulin (TBG) → ↑ Total T4/T3
• ↑ Iodine clearance → ↑ Iodine requirements
• hCG cross-reactivity → ↓ TSH in first trimester
• ↑ T4 transfer to fetus → ↑ Maternal T4 needs

Pregnancy-Specific Reference Ranges:

⚡ HIGH-YIELD: Hypothyroidism in Pregnancy

Overt Hypothyroidism:

• TSH above trimester-specific range + Low free T4
• Prevalence: 0.3-0.5% of pregnancies

Subclinical Hypothyroidism:

• TSH above trimester-specific range + Normal free T4
• Prevalence: 2-3% of pregnancies

Clinical Manifestations:

• Fatigue, cold intolerance, constipation
• Weight gain beyond expected pregnancy weight
• Depression, cognitive impairment
• Hair loss, dry skin
• Delayed reflexes

🔬 Maternal Complications:

• Preeclampsia (3× increased risk)
• Placental abruption
• Preterm delivery
• Postpartum hemorrhage
• Cesarean delivery

Fetal/Neonatal Complications:

• Impaired neurocognitive development
• Low birth weight
• Fetal demise
• Congenital anomalies

Screening Indications:

• Family history of thyroid disease
• Personal history of thyroid dysfunction
• Goiter
• Autoimmune disease
• Previous pregnancy complications
• Infertility history
• Age >30 years
• Morbid obesity (BMI >40)
• Use of amiodarone or lithium
• Type 1 diabetes

⚠️ PEARL: Universal screening remains controversial, but targeted screening based on risk factors is recommended by most guidelines.

Hypothyroidism Treatment:

Levothyroxine Dosing:

• Overt hypothyroidism: Start 1.6 μg/kg/day (typically 100-150 μg daily)
• Subclinical hypothyroidism: Start 25-50 μg daily
• Pre-existing hypothyroidism: Increase dose by 25-50 μg daily upon pregnancy confirmation

Monitoring:

• Check TSH every 4 weeks until target achieved
• Target: TSH in lower half of trimester-specific range
• Monitor every 4-6 weeks during pregnancy
• Postpartum: Return to pre-pregnancy dose, recheck in 6 weeks

Levothyroxine Adjustment Algorithm:

TSH >2.5 mIU/L in 1st trimester OR TSH >3.0 mIU/L in 2nd/3rd trimester ↓ Increase dose by 12.5-25 μg ↓ Recheck TSH in 4 weeks ↓ Repeat until target achieved

⚡ HIGH-YIELD: Hyperthyroidism in Pregnancy

Causes:

1. Gestational transient thyrotoxicosis (GTT) - 60-70%

   • hCG-mediated, self-limiting
   • Peaks at 8-14 weeks
   • No treatment needed

2. Graves' disease - 85% of pathological hyperthyroidism

   • TSH receptor antibodies (TRAb) positive
   • May improve in 2nd/3rd trimester
   • Risk of fetal/neonatal thyrotoxicosis

3. Other: Toxic nodular goiter, thyroiditis

Diagnostic Differentiation:

Treatment of Graves' Disease:

Antithyroid Drugs:

• First trimester: Propylthiouracil (PTU) 50-150 mg TID
  • Lower teratogenic risk vs. methimazole
• Second/Third trimester: Methimazole 5-15 mg BID
  • Switch from PTU due to hepatotoxicity risk

Monitoring:

• Free T4/T3 every 2-4 weeks
• Target: Free T4 in upper normal range
• TRAb levels at 18-22 weeks and 30-34 weeks
• Liver function tests if on PTU

Beta-blockers:

• Propranolol 40-120 mg daily for symptomatic relief
• Avoid atenolol (fetal growth restriction)

⚠️ PEARL: Monitor for fetal thyrotoxicosis if TRAb levels elevated (>3× upper normal). Signs include fetal tachycardia >160 bpm, IUGR, polyhydramnios.

Contraindications to antithyroid drugs:

• Radioiodine absolutely contraindicated
• Surgery only for severe cases unresponsive to medical therapy

The postpartum period represents a critical transition requiring continued monitoring for pregnancy-related complications and planning for future pregnancies.

Postpartum Preeclampsia:

• Can occur up to 6 weeks postpartum
• 25% of cases develop postpartum without antepartum preeclampsia
• Same diagnostic criteria as antepartum
• Management: Antihypertensives, magnesium sulfate if severe

HELLP Syndrome Recovery:

• Monitor platelet count, liver enzymes until normalization
• May worsen initially postpartum before improvement
• Consider plasmapheresis for severe, persistent cases

Long-term Cardiovascular Risk: ⚠️ PEARL: Women with preeclampsia have 2-4× increased lifetime risk of cardiovascular disease.

Follow-up Recommendations:

• Annual blood pressure monitoring
• Cardiovascular risk assessment
• Lifestyle modifications (diet, exercise, weight management)
• Consider low-dose aspirin for high-risk patients

Gestational Diabetes Postpartum Management:

Immediate Postpartum (24-48 hours):

• Discontinue all diabetes medications
• Monitor for hypoglycemia
• Standard diabetic diet until discharge

6-12 Week Follow-up: 75g Oral Glucose Tolerance Test (2-hour)

Long-term Management:

• Annual diabetes screening with fasting glucose or HbA1c
• 50% develop Type 2 diabetes within 10 years
• Preconception counseling for future pregnancies
• Breastfeeding encouraged (reduces diabetes risk)

Thyroid Disease Postpartum:

Postpartum Thyroiditis:

• Occurs in 5-10% of women
• Biphasic: Hyperthyroid (1-4 months) → Hypothyroid (4-8 months)
• Often resolves by 12 months postpartum
• High risk of permanent hypothyroidism (20-30%)

Management Algorithm:

Postpartum thyroid dysfunction ↓ Check TSH, Free T4 at 6 weeks ↓ ┌─────────┴─────────┐ ↓ ↓ Hypothyroid Hyperthyroid ↓ ↓ Start levothyroxine Beta-blockers for symptoms ↓ ↓ Monitor every 6-8 weeks Monitor, expect resolution Check for hypothyroid phase

Pre-existing Hypothyroidism:

• Return to pre-pregnancy levothyroxine dose
• Recheck TSH in 6-8 weeks
• Annual monitoring thereafter

Breastfeeding Considerations:

• Levothyroxine: Safe during breastfeeding
• Antithyroid drugs: PTU preferred over methimazole
• Monitor infant for signs of thyroid dysfunction

Preconception Counseling for Future Pregnancies:

• Risk recurrence: Preeclampsia 15-20%, GDM 35-70%, thyroid disease variable
• Optimization of chronic conditions
• Folic acid supplementation
• Low-dose aspirin if indicated
• Thyroid function optimization
• Diabetes screening and management