Pharmacology of Obstetrics
Hyperemesis gravidarum (HG) is severe, persistent vomiting in pregnancy causing dehydration, electrolyte imbalance, ketosis, and >5% weight loss. It affects 0.3–3% of pregnancies and requires urgent medical care.
Epidemiology
- Peak: 6–12 weeks
- Risk: primigravida, multiples, molar pregnancy
Etiology
Hormonal
- ↑hCG, estrogen
- Molar/multiple pregnancy
GI
- Delayed emptying
- H. pylori
Other
- Thyroid stimulation
- Stress, genetics
Pathophysiology
hCG/estrogen → vomiting center → dehydration → hypochloremic alkalosis, hypokalemia, ketonuria.
Severe: Wernicke’s (B1 deficiency), liver dysfunction.
Clinical Features
- Intractable vomiting
- Dehydration signs
- Ketotic breath
- Weight loss, oliguria
Investigations
| Test | Finding |
|---|---|
| Urinalysis | Ketonuria |
| Electrolytes | ↓K⁺, ↓Cl⁻ |
| LFTs | ↑AST/ALT |
| Ultrasound | Rule out molar |
Management
Rehydration
- IV NS/RL + KCl
- Thiamine 100mg IV before dextrose
Anti-emetics
| Drug | Dose |
|---|---|
| Pyridoxine | 25–50 mg TDS |
| Doxylamine | Safe, sedating |
| Ondansetron | Refractory cases |
Avoid steroids in 1st trimester.
Key Takeaways
- HG = vomiting + dehydration + ketonuria
- Thiamine before dextrose
- Anti-emetics: B6, antihistamines, ondansetron
- Resolves by 20 weeks
- Complications: Wernicke’s, IUGR
Conclusion
HG is treatable with early IV fluids, thiamine, and anti-emetics. Psychological support is key.
HG is not just morning sickness — it’s a medical emergency.