🤰 Hyperemesis Gravidarum — Overview
Hyperemesis Gravidarum (HG) is severe, persistent nausea and vomiting in pregnancy that leads to dehydration, electrolyte imbalance, nutritional deficiency, and significant impairment of daily function.
HG vs Normal Morning Sickness:
Normal morning sickness: nausea ± vomiting, usually 6–12 weeks, manageable, no weight loss
Hyperemesis Gravidarum: persistent vomiting, dehydration, weight loss >5% of pre-pregnancy weight, ketonuria, electrolyte disturbance → requires medical intervention
Epidemiology
- Affects 0.3–3% of pregnancies
- Leading cause of hospitalisation in first trimester
- Peak onset: 4–10 weeks gestation; usually resolves by 20 weeks (but persists throughout pregnancy in ~10%)
Risk Factors
Increased Risk
- Multiple pregnancy (twins/triplets)
- Molar pregnancy (very high hCG)
- Previous HG in prior pregnancy (70% recurrence risk)
- Female foetus
- Thyroid disease
- Helicobacter pylori infection
- Family history (mother with HG)
- Psychiatric history (anxiety, depression)
Pathophysiology
- Rising hCG (peak at 10–12 weeks) stimulates thyroid and nausea pathways
- Genetic predisposition (GDF15 gene variants recently identified)
- Oestrogen elevation
- Psychosocial factors contribute but are NOT the primary cause
- Helicobacter pylori co-infection may worsen symptoms
📊 Clinical Assessment
PUQE Score — Pregnancy-Unique Quantification of Emesis
Validated severity tool for HG:
| Question | Score 1 | Score 2 | Score 3 | Score 4 | Score 5 |
|---|
| Hours of nausea/day | ≤1h | 2–3h | 4–6h | 7–9h | ≥10h |
| Vomiting episodes/day | 0 | 1–2 | 3–4 | 5–6 | ≥7 |
| Retching episodes/day | 0 | 1–2 | 3–4 | 5–6 | ≥7 |
| Total PUQE Score | Severity |
|---|
| 3–6 | Mild — oral antiemetics, oral fluids, rest |
| 7–12 | Moderate — consider admission, IV fluids, IV antiemetics |
| 13–15 | Severe — admit, IV rehydration, thiamine, IV antiemetics |
Criteria for Hospital Admission
- Persistent vomiting despite outpatient antiemetics
- Clinical dehydration (dry mucous membranes, reduced skin turgor, oliguria)
- Weight loss >5% of pre-pregnancy weight
- Ketonuria (2+ or more)
- Electrolyte abnormalities (low K⁺, low Na⁺)
- Unable to tolerate oral fluids
Investigations on Admission
- U&E, LFTs (transaminase elevation common in HG)
- FBC (haemoconcentration from dehydration)
- TFTs (transient hyperthyroidism of HG — TSH suppressed, fT4 elevated; NOT true thyroid disease; resolves without treatment)
- Urinalysis — urine ketones, proteinuria (UTI exclusion)
- Ultrasound — exclude molar pregnancy, confirm viable intrauterine pregnancy, check for twins
- Blood glucose — hypoglycaemia from vomiting
Transient hyperthyroidism in HG: hCG cross-reacts with TSH receptor → TSH suppressed + elevated fT4. This is NOT Graves' disease — thyroid antibodies are negative, symptoms are HG-specific, resolves with HG treatment. Do NOT start antithyroid treatment unless true Graves' disease confirmed.
💊 Management of HG
Step 1: IV Rehydration
- Hartmann's solution (Ringer's Lactate) or 0.9% NaCl with KCl additions — preferred over dextrose-only
- Avoid dextrose-only fluids until thiamine given (risk of precipitating Wernicke's encephalopathy)
- Initial rate: 1L over 2–4 hours (guided by degree of dehydration)
- Replace potassium: add KCl 20–40 mmol per litre if hypokalaemic
- Monitor urine output (target >0.5 mL/kg/hour), U&E twice daily until stable
THIAMINE FIRST — BEFORE DEXTROSE FLUIDS. IV thiamine (Pabrinex or thiamine 100 mg IV/IM) must be given BEFORE any dextrose-containing fluids. Dextrose in a thiamine-depleted patient can precipitate acute Wernicke's encephalopathy (irreversible brain damage). See complications tab.
Step 2: Antiemetics
| Drug | Route | Safety | Notes |
|---|
| Cyclizine 50 mg | IV/IM/oral | Safe in pregnancy | First-line; TDS dosing |
| Promethazine 12.5–25 mg | IV/IM/oral | Safe in pregnancy | Causes sedation — useful at night |
| Metoclopramide 10 mg | IV/oral | Safe (avoid prolonged use) | Risk of extrapyramidal effects with prolonged use; use short-term |
| Ondansetron 4–8 mg | IV/oral | Generally safe (avoid 1st trimester if possible) | Effective; small QT prolongation risk; historical controversy re: cardiac effects resolved |
| Prochlorperazine 12.5 mg | IM/oral | Second-line | Avoid IV (hypotension) |
Step 3: Thiamine Supplementation
Thiamine (Vitamin B1) supplementation is mandatory in HG:
IV thiamine (Pabrinex 1+2 IV diluted): give immediately on admission BEFORE dextrose
Then oral thiamine 25–50 mg TDS throughout HG episode
This prevents Wernicke's encephalopathy
Step 4: Nutritional Support
- Small, frequent, low-fat meals once tolerating oral intake
- Cold foods often better tolerated (less smell-induced nausea)
- Ginger supplements — some evidence for mild benefit
- Acupressure wristbands (P6 point) — some patients find helpful
- Nasogastric feeding if oral intake persistently inadequate (>72h)
- TPN (via central line) rarely required — consider if weight loss >10% and enteral route not possible
Corticosteroids (Refractory HG)
- Hydrocortisone IV or prednisolone oral used for severe refractory HG
- Meta-analyses show modest benefit; avoid in first 10 weeks (minimal risk of oral cleft)
- Taper gradually — do not abruptly stop
Psychological Support
- HG causes significant psychological morbidity — depression, anxiety, PTSD
- Acknowledge severity and impact; avoid minimising ("just morning sickness")
- Referral to psychology/perinatal mental health team if needed
- PREGNANCY SICKNESS SUPPORT: signpost to patient support organisations
⚠️ Complications of HG
1. Wernicke's Encephalopathy (Most Critical Complication)
Wernicke's Encephalopathy = Acute thiamine (Vitamin B1) deficiency. Can cause irreversible brain damage and death. PREVENT by giving thiamine BEFORE dextrose in ANY vomiting patient.
- Triad: Confusion + Ophthalmoplegia (eye movement problems) + Ataxia
- Not all three features always present — confusion alone in a malnourished vomiting patient warrants IV thiamine
- If untreated: Korsakoff syndrome (irreversible anterograde amnesia, confabulation)
- Treatment: IV thiamine (Pabrinex) 500 mg TDS for 3 days then 250 mg OD
2. Mallory-Weiss Tear
- Longitudinal mucosal tear at gastro-oesophageal junction from forceful vomiting
- Presents as haematemesis (blood in vomit) after repeated vomiting
- Usually self-limiting; severe bleeding may require endoscopy
- OGD if persistent haematemesis
3. Electrolyte Disturbances
- Hypokalaemia (most common — K⁺ lost in vomit)
- Hyponatraemia (from vomiting + hypotonic fluid replacement)
- Hypochloraemic metabolic alkalosis (HCl lost in vomit)
- Replace potassium guided by U&E results
4. Foetal Concerns
- Mild HG: generally no adverse foetal outcomes
- Severe/prolonged HG with significant weight loss: low birthweight, preterm birth risk
- Foetal monitoring as per obstetric team guidance
- HG does NOT increase miscarriage risk
5. VTE Risk
Dehydration + reduced mobility + pregnancy = high VTE risk. LMWH thromboprophylaxis should be considered in hospitalised HG patients per VTE risk assessment.