Hyperemesis gravidarum consists of the most common cause of persistent severe nausea and vomiting before 20 weeks of pregnancy and the most common cause of hospitalisation during the first half of pregnancy.

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
  1. Antacids/Reflux management:
  • First line: Mylanta, Gaviscon
  • Second line: Ranitidine (category B1)
  • Third line: Omeprazole (PPIs, category B3)
  1. 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


References

FOAMed

Publications

Fellowship Notes

Dr Jessica Hiller LITFL Author

Doctor at King Edward Memorial Hospital in Western Australia. Graduated from Curtin University in 2023 with a Bachelor of Medicine, Bachelor of Surgery. I am passionate about Obstetrics and Gynaecology, with a special interest in rural health care.

Dr James Hayes LITFL author

Educator, magister, munus exemplar, dicata in agro subitis medicina et discrimine cura | FFS |

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