Hyperemesis gravidarum

Hyperemesis gravidarum is defined by:

• Persistent, severe nausea and vomiting
• Onset before 20 weeks gestation
• Ketosis
• Weight loss >5% of pre-pregnancy weight

Affects ~1% of pregnancies, while milder “morning sickness” occurs in up to 70%.

Pathophysiology

Associated with elevated levels of human chorionic gonadotrophin (hCG) from the placenta.

• Begins by 9–10 weeks gestation
• Peaks at 11–13 weeks
• Resolves by 12–14 weeks in most
• May persist beyond 20 weeks in 10% of cases

Despite the term “morning sickness”, symptoms may occur at any time of day.

Causes

1. Idiopathic
2. Hyperplacentosis:
   • Multiple pregnancy
   • Diabetes
   • Rhesus Isoimmunization
3. Hydatidiform mole
4. Less common: UTI, Hepatitis

Complications

1. Dehydration
2. Electrolyte imbalance
3. Mallory-Weiss tears
4. Gastric reflux with oesophagitis
5. Wernicke’s encephalopathy (without thiamine)
6. Abnormal LFTs (up to 50% of cases)

Clinical Assessment

Hyperemesis is a diagnosis of exclusion.

Mild/Moderate:

• Vomiting ≥2x/day
• Ketones 1+
• Requires antiemetics

Severe:

• Vomiting ≥2x/day
• Ketones 2+
• IV rehydration required
• Weight loss

Investigations

Bloods:

• FBE
• U&Es / Glucose
• LFTs (often elevated)
• TSH (often suppressed)
• BHCG (to assess for molar pregnancy or multiples)

Urine:

• MSU for M&C (exclude UTI)
• FWT (ketones)

Ultrasound:

• Exclude molar pregnancy
• Confirm singleton vs multiple gestation

Management

1. IV Fluids:
   • Rehydration as required
2. Electrolyte Correction:
   • Replace potassium if needed
3. Antiemetics:

Mild cases:

• Pyridoxine (Vitamin B6) 50 mg up to QID or 200 mg nocte
• Add Doxylamine (H1 antagonist) 12.5–25 mg orally
• Add sedating antihistamines:
  • Promethazine 10–25 mg TID-QID
  • Dimenhydrinate 50 mg TID-QID
• Add:
  • Metoclopramide 10 mg TID (max 30 mg/day for ≤5 days)
  • Or Prochlorperazine 5–10 mg BID-TID or 25 mg PR

Moderate/Severe cases:

• Ondansetron 4 mg PO/IV/IM Q8–12h
• Metoclopramide 10 mg IV/IM Q8h
• Prochlorperazine 12.5 mg IM Q8h
• Promethazine 12.5–25 mg IM Q4–6h
• Chlorpromazine 25–50 mg IV/IM Q6–8h (max 75 mg/day)
• Steroids: Oral corticosteroids only in consultation with O&G

4. Antacids/Reflux management:

• First line: Mylanta, Gaviscon
• Second line: Ranitidine (category B1)
• Third line: Omeprazole (PPIs, category B3)

5. Thiamine Supplementation:

• 100 mg orally daily if severe or prolonged vomiting
• Prevent Wernicke’s encephalopathy

Continue treatment until patient can tolerate oral fluids and ketonuria resolves.

Disposition

Full ward admission if persistent vomiting, weight loss, or IV antiemetics required

Mild cases: Trial of ED IV fluids and reassessment. Discharge if improved, with GP follow-up

Moderate/Severe cases: Consider hospital admission

SSU admission if not critically unwell

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References

FOAMed

• Nickson C. Ovarian Hyperstimulation Syndrome. CCC

Publications

• London V, Grube S, Sherer DM, Abulafia O. Hyperemesis Gravidarum: A Review of Recent Literature. Pharmacology. 2017;100(3-4):161-171.