Toxicosis in Pregnancy

1. Early toxicosis - nausea, vomiting, and hyperemesis gravidarum (first trimester)
2. Late toxicosis - hypertensive disorders including preeclampsia, eclampsia, and HELLP syndrome (second/third trimester)

Part 1: Early Toxicosis - Nausea, Vomiting & Hyperemesis Gravidarum

Nausea and Vomiting of Pregnancy (NVP)

Hyperemesis Gravidarum

• Weight loss >5% of total body weight
• Dehydration
• Starvation metabolism with prolonged ketonemia and ketonuria

• Rising estradiol and hCG levels
• Maternal cytokines
• Helicobacter pylori infection (significantly associated; treating H. pylori decreases vomiting)
• Studies suggest early treatment of NVP may prevent progression to hyperemesis

• Wernicke encephalopathy (vitamin B1 deficiency) - in the mother
• Bleeding diathesis (vitamin K deficiency) - in the fetus
• Abnormal liver function (bilirubin, alkaline phosphatase elevations that resolve with treatment)

• Urinalysis (ketones, specific gravity, infection)
• Serum chemistry (hypokalemia, contraction alkalosis, elevated anion gap)
• Liver function tests

1. Rehydration: 2 L Ringer's lactate IV at 500 mL/hr
2. Thiamine (Vitamin B1) BEFORE any dextrose - to prevent Wernicke encephalopathy
3. Then dextrose-containing IV fluids (D5/0.45NS) until ketones clear
4. Antiemetics: Diclegis (doxylamine + B6) is first line
5. Potassium and magnesium repletion as needed
6. Refractory cases: methylprednisolone 16 mg PO/IV every 8 hours for 3 days (last resort)
7. If weight cannot be maintained: nasogastric enteral nutrition

• Rosen's Emergency Medicine, p. 3364

Part 2: Late Toxicosis - Hypertensive Disorders of Pregnancy

Overview

Preeclampsia

Pathogenesis

• Anti-angiogenic proteins: soluble FMS-like tyrosine kinase-1 (sFlt-1) and soluble endoglin
• These antagonize VEGF and TGF-β, causing systemic maternal endothelial dysfunction
• Inflammatory cytokines (TNF-α, IL-6) amplify the response

• Robbins & Kumar Basic Pathology, p. 702
• Guyton & Hall Medical Physiology, p. 1041

Diagnostic Criteria

• Blood pressure ≥ 140/90 mmHg on two occasions 4 hours apart
• Plus proteinuria OR evidence of end-organ damage (thrombocytopenia, renal insufficiency, impaired liver function, pulmonary edema, new-onset headache/visual disturbances)

Risk Factors

• Nulliparity (greatest population attributable fraction: 32.3%)
• Prior preeclampsia, antiphospholipid syndrome, chronic hypertension (25% develop preeclampsia), chronic renal disease
• Pregestational diabetes mellitus (20% overall; up to 70% in White's classes F/R)
• Obesity (increases risk ~3-fold; accounts for up to 1/3 of US cases)
• Multiple gestation (6.7% twins, 12.7% triplets, 20% quadruplets)
• Hydatidiform mole (70%!), extremes of maternal age, Black race (for severe forms)
• Creasy & Resnik's Maternal-Fetal Medicine

Signs and Symptoms of Severe Preeclampsia

• Cerebral: headache, dizziness, tinnitus, drowsiness, altered mental status
• Visual: blurred vision, scotomata, diplopia, amaurosis
• GI: nausea, vomiting, epigastric/RUQ pain (hepatic involvement)
• Renal: oliguria, anuria, hematuria

Organ Pathology

1. Hemorrhage into hepatic cellular columns (vasodilation)
2. Hepatic infarction (vasospasm)

HELLP Syndrome

Eclampsia

• Occurs in approximately 0.2% of pregnancies
• Mechanism: hypertensive encephalopathy, loss of cerebral vascular autoregulation
• Perinatal mortality: 2-8.6%
• Maternal mortality: <2%, mainly from intracranial hemorrhage

Management

Antihypertensive Therapy

• Systolic BP ≥ 160 mmHg, OR
• Diastolic BP ≥ 110 mmHg, if persistent for ≥15 minutes

• IV labetalol
• IV hydralazine
• Oral nifedipine

Seizure Prevention/Treatment

• Loading dose: 4-6 g IV over 15 minutes
• Maintenance: 1-3 g/hr continuous infusion
• Monitor: deep tendon reflexes, urine output, serum Mg levels
• Antidote: IV calcium gluconate

Definitive Treatment

Special Situations

• HELLP syndrome and severe preeclampsia with multisystem dysfunction: maternal-fetal medicine subspecialist consultation
• Inadequate local facilities: transfer to tertiary care center
• Creasy & Resnik's Maternal-Fetal Medicine, pp. 1057-1060
• Textbook of Family Medicine, p. 497

Prevention

Summary Classification

Pathogenesis of Early Toxicosis in Pregnancy - A Pathologist's Perspective

I. Epidemiological Framework (the Starting Point for Pathological Thinking)

• NVP affects 60-70% of all pregnant women; vomiting in >40%
• Onset: weeks 4-6; peak: weeks 8-12; resolution: week 20 in most
• Hyperemesis gravidarum (the severe, pathological end): <2% of pregnancies, defined by ketonuria + >5% weight loss from pre-pregnancy weight
• Recurs in subsequent pregnancies in 15-19% of previously affected women

• Sleisenger & Fordtran's Gastrointestinal and Liver Disease, p. 655
• Creasy & Resnik's Maternal-Fetal Medicine, p. 1564

II. The Central Pathological Mechanisms

1. The hCG Hypothesis (Primary Driver)

• Symptoms worsen precisely during the period of peak hCG concentrations (weeks 8-12)
• Conditions with higher hCG levels are universally associated with worse NVP and higher rates of HG:
  • Multiple gestation
  • Gestational trophoblastic disease (hydatidiform mole)
  • Trisomy 21 (which produces excess hCG)
  • Hydrops fetalis
• Symptoms improve as hCG falls in the second trimester

• Transient gestational thyrotoxicosis - hCG stimulates the TSH receptor, suppresses endogenous TSH, and elevates free T4
• Abnormal thyroid function tests are found in two-thirds of HG patients
• The resulting mild hyperthyroid state amplifies nausea (thyroid hormones modulate gastric motility and the central vomiting pathways)
• Importantly, this is not true hyperthyroidism - it resolves with delivery and does not require antithyroid treatment

2. Estrogen and Progesterone Effects on GI Motility

• Sleisenger & Fordtran's GI & Liver Disease, p. 655

3. The Gut-Derived Hormones: Ghrelin and Leptin

• Ghrelin (the "hunger hormone," produced in the gastric fundus): levels are altered in HG; its role in gastric motility means changes directly affect the rate of gastric emptying
• Leptin (produced by adipose tissue and the placenta): placental leptin secretion rises in early pregnancy and has been implicated in modulating the nausea response through central hypothalamic pathways
• Both are currently considered contributing factors rather than primary causes

4. The Central Vomiting Pathways - Neural Architecture of HG

• Located in the medulla oblongata
• Receives afferent signals from the vagus nerve (gut), vestibular apparatus, higher cortical centers, and the area postrema
• Coordinates the efferent motor act of vomiting via the phrenic nerve, spinal motor neurons, and cranial nerves

• Located at the floor of the fourth ventricle
• Lies outside the blood-brain barrier - directly sensitive to circulating chemical triggers (hCG, estrogen metabolites, toxins)
• Rich in dopamine (D2), serotonin (5-HT3), and substance P/NK1 receptors
• Circulating hCG and estrogen metabolites stimulate the CTZ → relay to the vomiting center → nausea and emesis
• This is why the nuclei of the solitary tract, raphe, and area postrema are thought to be the sites of steroid action (the mechanism by which corticosteroids rescue refractory HG)

• In HG, vomiting is triggered not only by chemical stimuli but by olfactory, auditory, and visual stimuli - reflecting a pathological lowering of the sensory threshold at the level of the NTS and cortical-limbic pathways
• Hyperolfaction (heightened smell sensitivity) is a hallmark symptom, consistent with increased CNS arousal of the emetic network

5. Helicobacter pylori - The Infectious Contribution

• Two meta-analyses show significantly increased rates of H. pylori infection in pregnant women with HG vs. uncomplicated NVP
• Proposed mechanism: H. pylori colonizes the gastric antrum, induces local mucosal inflammation (neutrophil infiltration, IL-8, TNF-α release), alters gastric emptying, and directly stimulates the vagus nerve
• The inflammatory cytokines produced by H. pylori gastritis may amplify the central vomiting response through the area postrema
• Symptomatic improvement has been documented after H. pylori eradication during pregnancy using non-teratogenic regimens
• Importantly, H. pylori itself does not cause HG, but acts as a disease modifier - amplifying the hormonal and neural triggers already in place

6. Psychoneuroimmunological and Psychosocial Factors

• Familial clustering of HG strongly implies a genetic predisposition - likely in genes governing hCG receptor sensitivity, serotonin transporter function, or central emetic threshold
• Psychological stress activates the hypothalamic-pituitary-adrenal (HPA) axis and alters GI motility via corticotropin-releasing hormone (CRH) - which also acts on peripheral mast cells in the gut mucosa, increasing permeability and enteric nerve excitability
• Women with prior psychiatric disorders have higher rates of HG hospitalization - though causality is bidirectional (HG causes psychological distress)

III. Pathological Consequences of Severe HG (What the Pathologist Sees)

Metabolic/Biochemical

• Hypokalemia, hyponatremia - from vomiting losses
• Contraction metabolic alkalosis - from loss of HCl
• Ketonemia/ketonuria - starvation metabolism; fat catabolism
• Elevated anion gap - in prolonged starvation
• Hypoamylasemia correction note: Hyperamylasemia occurs in ~25% of HG cases - caused by excessive salivary gland production stimulated by prolonged vomiting (not pancreatitis)
• Transaminase elevation (AST, ALT) in 25-40% + mild hyperbilirubinemia - from hepatic dysfunction secondary to malnutrition and fatty change; fully reversible

Neurological (Wernicke Encephalopathy)

• Thiamine (B1) is water-soluble and depleted rapidly when oral intake ceases
• Thiamine is an essential cofactor for pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, and transketolase - all required for aerobic glucose metabolism
• Administration of dextrose (glucose) WITHOUT thiamine first drives pyruvate through glycolysis, depleting the remaining thiamine and precipitating Wernicke encephalopathy
• Pathology of Wernicke: hemorrhagic necrosis and petechiae in the mammillary bodies, periventricular gray matter, periaqueductal region, and floor of the 4th ventricle
• Classic triad: ophthalmoplegia, ataxia, confusion

Fetal Consequences

• Vitamin K deficiency (fat-soluble, crosses placenta poorly when mother is deficient) → neonatal bleeding diatheses
• Low birth weight, SGA, prematurity, low 5-minute Apgar scores in infants of HG women with <7 kg gestational weight gain
• Rarely: esophageal Mallory-Weiss tears, pneumomediastinum (barotrauma from forceful vomiting), esophageal rupture (Boerhaave syndrome)
• Sleisenger & Fordtran's GI & Liver Disease, p. 655
• Creasy & Resnik's Maternal-Fetal Medicine, p. 1564
• Rosen's Emergency Medicine, p. 3364

IV. Integrated Pathogenetic Model

Trophoblast proliferation
        ↓
   ↑↑ hCG secretion
   ↙          ↘
Thyroid        Area Postrema
stimulation     (CTZ)
(↑ free T4,     stimulation
↓ TSH)                 ↓
     ↘           Vomiting Center
      → NTS/raphe ← (nucleus tractus
           ↑         solitarius)
   ↑ Estrogen         ↑
   ↑ Progesterone    Vagal input from
   (↓ GI motility,  H. pylori gastritis /
   ↓ LES tone)      GI dysmotility
           ↓
     NAUSEA / VOMITING
           ↓ (if severe / untreated)
   Starvation → Ketonuria → Wernicke
   Hypokalemia → Alkalosis → Fetal growth restriction

V. Why This Matters Pathologically

1. The degree of hCG/estrogen rise (amplified by multiple gestation, mole, trisomy 21)
2. Individual receptor sensitivity (genetic variation in hCG receptor, serotonin transporter)
3. Comorbid H. pylori gastritis (amplifies the afferent vagal signal)
4. Central emetic threshold (modulated by genetics, prior experience, psychosocial state)