RCOG Green-top Guideline
MRCOG Part 2
The Management of Nausea and Vomiting of Pregnancy and Hyperemesis Gravidarum
Definitions and Diagnosis
- NVP (nausea and vomiting of pregnancy): diagnosed when onset is before 16 weeks' gestation and other causes have been excluded. Affects up to 90% of pregnant women; typically starts weeks 4-7, peaks around week 9, resolves by week 20 in 90%.
- Hyperemesis gravidarum (HG): the severe form, affecting 0.3-3.6% of pregnancies. The 2024 edition adopts the international Windsor definition: nausea and vomiting, of which one is severe, beginning in early pregnancy, causing an inability to eat and drink normally and strongly limiting daily activities — dehydration signs are contributory rather than required. This replaces the older criterion of >5% pre-pregnancy weight loss plus dehydration plus electrolyte imbalance.
- Ketonuria is not an indicator of dehydration and should not be used to assess severity [Grade A] — a major change from the 2016 edition, which had included urine ketones as a severity marker.
Severity Scoring
- PUQE (Pregnancy-Unique Quantification of Emesis) score: a validated 24-hour symptom index (nausea episodes, vomiting episodes, retching) used to classify NVP as mild, moderate, or severe, and to track treatment response. Valid for mild-to-moderate NVP but not validated for severe NVP/HG.
- HELP (HyperEmesis Level Prediction) score: a newer validated tool (online calculator/app) used specifically to monitor severe NVP and HG over time and assess treatment response, complementing PUQE where it is not valid.
First- and Second-Line Antiemetics
- First line [Grade A]: antihistamines (H1 antagonists — promethazine, cyclizine, doxylamine, cinnarizine), phenothiazines (prochlorperazine, chlorpromazine, perphenazine), and the doxylamine/pyridoxine (vitamin B6) combination (Xonvea) — a delayed-release 10 mg doxylamine + 10 mg pyridoxine tablet and the only medicine licensed specifically for NVP in the UK.
- Second line [Grade B/C]: metoclopramide (safe and effective, but risk of extrapyramidal effects/oculogyric crisis limits it to second line; maximum 30 mg/24h or 0.5 mg/kg/24h, whichever is lower, for a maximum of 5 days; IV doses given as a slow bolus over ≥3 minutes) and ondansetron (safe and effective; a small absolute increase in orofacial clefting risk with first-trimester use — about 14 vs 11 per 10,000 births — should be weighed against the risks of poorly controlled HG).
- Corticosteroids [Grade A]: reserved for cases refractory to standard antiemetics — IV hydrocortisone 100 mg twice daily, then converted to oral prednisolone 40-50 mg daily, tapered to the lowest effective dose.
- Combination therapy across drug classes should be used if a single agent fails.
Complications
- Electrolyte derangement: hyponatraemia, hypokalaemia, low serum urea, raised haematocrit, and a hypochloraemic metabolic alkalosis (metabolic acidosis if severe). Daily U&E monitoring is required in women on IV fluids.
- Wernicke's encephalopathy: caused by thiamine (vitamin B1) deficiency; classic triad of confusion, ataxia, and ophthalmoplegia/nystagmus, often with blurred vision and hyporeflexia. Onset in HG is typically episodic and slow. A potentially fatal but preventable and reversible emergency — a systematic review of 177 cases found chronic cognitive impairment in 65.4%, pregnancy loss in 50%, and maternal death in 5%. Thiamine 100 mg orally TDS, or IV as part of vitamin B complex (Pabrinex), should be given to all women admitted with prolonged vomiting or severely reduced intake — especially before dextrose or parenteral nutrition, since dextrose can precipitate Wernicke's in a thiamine-deficient state.
- VTE risk: women admitted with HG should be offered LMWH thromboprophylaxis (VTE odds ratio ~2.5) unless contraindicated; can stop on discharge once vomiting resolves.
- Rehydration of choice: normal saline (0.9% NaCl) with added potassium chloride, guided by daily electrolyte monitoring; dextrose-only fluids should be avoided.
High-Yield Exam Points
- Ketonuria does NOT indicate dehydration/severity (2024 change) — do not use urine ketones to guide HG management decisions.
- PUQE scores mild-moderate NVP; HELP scores severe NVP/HG.
- Antiemetic order: antihistamines/phenothiazines/Xonvea (1st) → metoclopramide or ondansetron (2nd) → corticosteroids (refractory).
- Always give thiamine before dextrose/parenteral nutrition to prevent Wernicke's encephalopathy.
Source: RCOG Green-top Guideline No. 69 (2nd edition) (2024 (2nd edition; originally published June 2016). Published in *BJOG* 2024;00:1-30 (Nelson-Piercy et al.).)
Read the original on rcog.org.uk
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