Hyperemesis gravidarum
Description
- Severe end of the nausea/vomiting-of-pregnancy (NVP) spectrum
- Definition: intractable vomiting + one of: >5% pre-pregnancy weight loss, dehydration, electrolyte disturbance, ketonuria
- Typically begins 4-6 weeks gestation, peaks ~9 weeks
Epidemiology
- NVP ~70-80% of pregnancies (mostly mild)
- Hyperemesis gravidarum ~1-3% - commonest cause of hospital admission in early pregnancy
- Risk factors: multiple pregnancy, molar pregnancy, prior HG, hyperthyroidism, H. pylori, female fetus (weak association)
Aetiopathogenesis
- Rising beta-hCG correlates with symptom onset/severity - hence worse in multiple/molar pregnancy
- Oestrogen and progesterone -> gastric dysmotility
- Transient biochemical hyperthyroidism (hCG shares alpha-subunit with TSH) in up to 60% - usually resolves spontaneously, treat only if clinically thyrotoxic
- Genetic component (GDF15, IGFBP7 implicated) - explains familial clustering and recurrence
Diagnosis
Clinical - diagnosis of exclusion
- Confirm intrauterine pregnancy, exclude multiple/molar pregnancy (ultrasound)
- Exclude: UTI, gastroenteritis, hepatitis, pancreatitis, cholecystitis, DKA, thyrotoxicosis, molar pregnancy, appendicitis
PUQE score (Pregnancy-Unique Quantification of Emesis)
- Grades severity, guides escalation and response to treatment
Investigations
- UEC (hypokalaemia, hyponatraemia), FBE, LFT (mild transaminitis common), TFT, urine ketones/MCS, glucose
- Severe cases: consider thiamine level before glucose-containing fluids
Management
Community / mild
- Dietary measures - small frequent meals, avoid triggers
- First-line antiemetics: doxylamine-pyridoxine (Vitamin B6) combination, or single-agent pyridoxine/doxylamine
- Ginger - adjunct, modest evidence
Escalating pharmacotherapy - stepwise
| Step | Agent |
|---|---|
| 1 | Doxylamine-pyridoxine +/- ginger |
| 2 | Add metoclopramide or prochlorperazine or ondansetron |
| 3 | Combination of above; add promethazine |
| 4 | Corticosteroids (e.g. prednisolone) - refractory cases only |
- Ondansetron - widely used; reassuring large cohort data but a small absolute increase in oral clefts/cardiac defects with 1st trimester use debated - discuss with patient
- Metoclopramide - limit duration (extrapyramidal effects)
Admission criteria
- Ketonuria + failure of oral antiemetics, >5% weight loss, electrolyte derangement, unable to tolerate oral fluids
Inpatient
- IV fluids - normal saline, NOT dextrose first (risk of Wernicke encephalopathy if thiamine-deplete) - give thiamine before/with any dextrose
- Correct K+/Na+ - correct hyponatraemia slowly (osmotic demyelination risk)
- IV antiemetics; consider enteral (nasogastric/nasojejunal) feeding or, rarely, parenteral nutrition if refractory
- Thromboprophylaxis - immobility + pregnancy = VTE risk
- Psychological support - HG associated with anxiety/depression, termination requests in severe unsupported cases
Associations
- Transient biochemical hyperthyroidism
- Mallory-Weiss tear, oesophagitis
- Wernicke encephalopathy (if thiamine deficient and given glucose without replacement) - preventable, still reported
- Ptyalism, mild transaminitis
Natural history & complications
- Most resolve by 20 weeks; small proportion persist to term
- Recurrence in future pregnancy ~15-20%, higher if severe
- Adequately treated HG - fetal outcomes generally reassuring
- Undertreated, severe HG - association with low birth weight, preterm birth
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