Nausea & Vomiting in Pregnancy Algorithm

Safety

Red Flags — Exclude Serious Conditions Presenting as NVP

Done

Not all vomiting in pregnancy is NVP. Exclude dangerous non-obstetric and obstetric causes, and identify hyperemesis gravidarum requiring hospital admission.

Haematemesis Blood or coffee-ground material in vomit → Same-day assessment. Mallory-Weiss tear (common in HG), oesophagitis, rarely peptic ulcer. GI surgery review if haemodynamically unstable.

Signs of dehydration/severe HG Ketonuria ++ on dipstick + unable to keep any fluids down + weight loss >5% + postural hypotension → Same-day hospital admission for IV fluids.

Neurological symptoms Diplopia, nystagmus, confusion, ataxia with vomiting → 999/Same-day (Wernicke's encephalopathy from thiamine deficiency in severe HG — life-threatening)

Abdominal pain + vomiting Epigastric pain (UTI, appendicitis, cholecystitis, pancreatitis, pre-eclampsia if >20 weeks), severe RUQ pain (HELLP syndrome >20 weeks, gallstones) → Same-day assessment

Fever + vomiting Temperature >37.5°C + nausea/vomiting → urine MC&S same day (UTI/pyelonephritis common in pregnancy), consider gastroenteritis, appendicitis

Onset after 12 weeks / new vomiting 2nd trimester NVP typically resolves by 12–16 weeks. New vomiting after 16 weeks → exclude UTI, reflux, appendicitis, pre-eclampsia, molar pregnancy, AFLP

Molar pregnancy features Severe vomiting >expected + vaginal bleeding + uterus larger than dates + bilateral theca-lutein cysts → Same-day EPU (mole produces very high βhCG driving severe NVP)

Psychiatric emergency Suicidal ideation secondary to severe distress from HG → Same-day mental health assessment. HG has higher rates of termination and maternal suicide than other pregnancy complications.

Wernicke's encephalopathy is a rare but catastrophic complication of hyperemesis gravidarum, caused by thiamine (B1) depletion from persistent vomiting and inadequate intake. The classic triad (confusion, ophthalmoplegia, ataxia) may be incomplete — ophthalmological signs alone should trigger IV thiamine immediately. Untreated, it causes irreversible Korsakoff's syndrome and death. RCOG Green-top 69 mandates prophylactic oral thiamine in ALL women with hyperemesis gravidarum. Appendicitis in pregnancy is notoriously difficult to diagnose because the appendix migrates superiorly as the uterus enlarges — the pain may be atypical and peritonism masked by the gravid uterus.

Diagnose

Confirm & Score Severity — PUQE Score

Done

Use the validated Pregnancy-Unique Quantification of Emesis (PUQE) score to classify severity and guide treatment intensity. Document score in notes.

PUQE scoring

Three questions, each scored 1–5: (1) Hours of nausea per day (2) Episodes of vomiting per day (3) Episodes of retching per day. Total score 3–15.

Mild NVP

PUQE ≤6. Nausea but able to maintain oral intake. No ketonuria. Manage with lifestyle measures ± first-line antiemetics in primary care.

Moderate NVP

PUQE 7–12. Significant symptoms affecting function. Some dehydration risk. Medical treatment in primary care, close monitoring, low threshold for admission.

Severe HG

PUQE ≥13 OR ketonuria ++ OR weight loss >5% OR unable to keep oral fluids down → Hospital admission for IV hydration, IV antiemetics, thiamine.

HG diagnostic criteria

Persistent nausea/vomiting causing dehydration, ketonuria, electrolyte imbalance, >5% weight loss. Affects 0.3–1.5% of pregnancies. Peak at 8–12 weeks, may persist beyond 20 weeks.

Baseline weight

Weigh at every appointment and document. Percentage weight loss drives admission decision. Use pre-pregnancy weight as baseline if available.

The PUQE score has been validated against 24-hour vomiting diaries and correlates with objective measures of dehydration. Using it consistently prevents under-treatment (dismissing moderate HG as normal morning sickness) and over-medicalisation of mild NVP. RCOG Green-top 69 (2024) specifically recommends PUQE scoring. Up to 80% of UK women with HG report that their symptoms were initially dismissed as normal morning sickness — this has been associated with significant psychological harm and unnecessary delays to effective treatment.

Diagnose

Classify Severity — NVP vs HG vs Other Cause

Done

Distinguishing NVP from HG determines management setting. Identifying non-pregnancy causes prevents diagnostic anchoring.

Normal NVP

Nausea ± vomiting. Onset 4–8 weeks, peak 8–12 weeks, resolves by 16–20 weeks in 90%. Able to maintain some oral intake. No significant weight loss. No ketonuria. Affects 70–80% of pregnancies.

Moderate NVP

Significant impact on daily function. Some dehydration but maintaining minimal oral intake. May have trace-small ketonuria. Medical treatment indicated.

Hyperemesis Gravidarum (HG)

Intractable vomiting, ketonuria ++, dehydration, electrolyte imbalance (hypokalaemia, hyponatraemia), weight loss >5%, thiamine deficiency risk. Hospital management.

Non-pregnancy causes

Consider if: onset after 10 weeks, worsening after 20 weeks, diarrhoea prominent, fever, localised abdominal pain, urinary symptoms, headache. Investigate separately.

Twin/molar pregnancy

Higher βhCG → more severe NVP/HG. Confirm by USS. Molar pregnancy: vomiting out of proportion + bleeding + large uterus.

Psychological impact

Screen ALL women with HG: PHQ-9/GAD-7 at first presentation. HG has 30–50% rate of depression/anxiety. Do not normalise psychological distress.

The distinction between NVP and HG is not merely semantic — it determines whether treatment is lifestyle advice, oral medication, or IV hospitalisation. The common clinical error is treating moderate HG with oral antiemetics alone when IV fluids are needed, leading to serial GP visits, A&E attendances, and prolonged suffering. The Pregnancy Sickness Support charity estimates that 50% of HG patients are admitted 3 or more times before an adequate inpatient treatment plan is established — early aggressive treatment in the community prevents this. Co-existing thyroid dysfunction (gestational thyrotoxicosis) occurs in 60% of HG — βhCG cross-stimulates TSH receptors.

Diagnose

Targeted Examination

Done

Focused examination to assess hydration status and exclude non-obstetric causes.

Vital signs

HR (tachycardia → dehydration/infection), BP (hypotension → severe dehydration; raised + headache → pre-eclampsia if >20 weeks), Temperature (fever → infection), RR (ketoacidosis in severe HG)

Hydration assessment

Skin turgor, dry mucous membranes, sunken eyes, postural hypotension (drop >20 mmHg systolic sitting→standing). Severe dehydration signs → admission.

Weight

Weigh every presentation. Calculate % weight loss from baseline. >5% = significant dehydration/malnutrition → admission threshold.

Abdominal examination

Tenderness — epigastric (pancreatitis, PUD, pre-eclampsia), RUQ (cholecystitis, HELLP >20w), RIF (appendicitis). Uterine size: larger than dates → molar pregnancy, multiple pregnancy.

Neurological

If confusion, ataxia, diplopia, or nystagmus present → EMERGENCY IV thiamine immediately + 999/hospital (Wernicke's encephalopathy)

Urine dipstick

Ketones: trace = dehydration, ++ to +++ = significant metabolic derangement. Protein/leucocytes/nitrites: UTI/pyelonephritis. Do at every consultation

Postural hypotension (drop >20mmHg systolic) is a sensitive sign of clinically significant dehydration in pregnancy and mandates same-day hospital referral for IV fluid assessment. Ketones ++ on dipstick indicate the body is catabolising fat due to inadequate carbohydrate intake — this accelerates thiamine depletion and indicates the patient cannot safely continue on oral management alone. Gestational hypertension and pre-eclampsia can cause nausea and vomiting, particularly with RUQ pain (hepatic capsule stretching from HELLP) — missing this at 20+ weeks gestation is a critical safety failure.

Diagnose

Investigations

Done

RCOG Green-top 69: investigate to assess severity, identify complications, and exclude other diagnoses. Investigations guide admission threshold.

Urine dipstick
Every consultation

Ketones (severity of HG), protein (pre-eclampsia if >20 weeks), leucocytes/nitrites (UTI/pyelonephritis). Ketonuria +++ = same-day admission.

MSU

If leucocytes or nitrites positive → send MSU MC&S. UTI and pyelonephritis are common NVP mimics and worsen NVP. Treat with pregnancy-safe antibiotics (nitrofurantoin not in 3rd trimester).

Bloods — moderate/severe HG

U&Es (hypokalaemia, hyponatraemia — electrolyte replacement needed), FBC (haemoconcentration in dehydration), LFTs (transiently raised in 50% HG — usually benign), TFTs (gestational thyrotoxicosis — don't treat unless TSH persistently suppressed with symptoms)

Thiamine levels

If severe HG: check thiamine (B1). Do NOT delay treatment while waiting results — give empiric thiamine if ketonuria ++ or persistent vomiting >3 weeks (RCOG recommendation).

USS pelvis

Confirm intrauterine pregnancy, gestation, singleton vs multiple, exclude molar pregnancy. Should be performed in all new presentations if not already done at booking.

When NOT to investigate

Mild NVP with normal dipstick, normal examination, maintaining oral intake → no blood tests needed. Do not over-investigate self-limiting mild NVP.

Hypokalaemia (K+ <3.0 mmol/L) from recurrent vomiting causes cardiac arrhythmias — oral rehydration is insufficient to correct this and IV replacement is mandatory. Gestational thyrotoxicosis (suppressed TSH, raised fT4 driven by βhCG) occurs in 60% of HG but is transient and does not require antithyroid treatment unless TSH remains suppressed beyond 16–20 weeks with clinical hyperthyroidism — treating it causes fetal hypothyroidism. LFT elevation in HG (raised ALT/AST) is usually benign and resolves with treatment — but must be distinguished from AFLP (acute fatty liver of pregnancy), which is life-threatening and presents with HG + jaundice + coagulopathy later in pregnancy.

Refer

Referral & Admission Criteria

Done

Hospital admission criteria are clear — do not delay when threshold met. Day-case IV rehydration units (where available) can prevent full inpatient admissions.

999 / Emergency

Neurological signs (Wernicke's encephalopathy: confusion, diplopia, ataxia) → IV thiamine + 999 immediately · Haematemesis with haemodynamic instability · Signs of severe sepsis (pyelonephritis) · Suspected molar pregnancy + haemodynamic compromise

Same-day hospital

Ketonuria +++ · Unable to keep any fluids/medications down for 24h · Weight loss >5% · Postural hypotension · PUQE ≥13 · Electrolyte abnormalities (K+ <3.0, Na+ <130) · Complicating factors (UTI, mental health crisis, suicidal ideation)

Day-case/community IV unit

Moderate HG (PUQE 7–12) + ketonuria ++ but maintaining minimal fluid → IV fluids + IV antiemetics + thiamine as day case. Prevents admission if available locally.

Obstetric/midwifery team

All HG patients should be under joint care with obstetric team. Alert booking midwife. HG may require consultant-led care.

Primary care management

Mild-moderate NVP (PUQE ≤12), maintaining some oral intake, no red flags, no ketonuria ++ → manage in primary care with antiemetics, hydration support, thiamine, close follow-up.

The availability of day-case IV rehydration units in early pregnancy units (EPUs) has transformed HG management — replacing what previously required 3–5 day inpatient admissions with 4–6 hour day-case visits. RCOG Green-top 69 endorses this model. GPs who proactively refer to EPU day cases prevent the sequence of: GP appointment → inadequate oral treatment → deterioration → A&E attendance → emergency admission → prolonged inpatient stay. Early intervention prevents this spiral. Mental health crisis in HG is underestimated — a 2017 study found 39% of women with severe HG reported suicidal ideation, 30% considered termination solely due to NVP symptoms. Crisis plan should be documented.

Treat

Treatment Ladder — Antiemetics & Supportive Care

Done

RCOG Green-top 69 and NICE NG201: antiemetics are safe and recommended in pregnancy. Do NOT withhold treatment due to unfounded teratogenicity concerns — undertreated HG causes harm to mother and fetus.

Mild NVP (PUQE ≤6)

Ginger / P6 acupressure Non-drug first

Ginger 250mg QDS (capsules or tea) — modest evidence. P6 (Neiguan) acupressure wristbands — used as adjunct. If insufficient after 24–48h → antiemetic.

Moderate NVP (PUQE 7–12)

Prochlorperazine 5–10mg TDS First-line antiemetic

Or cyclizine 50mg TDS. Or promethazine 25mg TDS/nocte. All RCOG Category A safety in pregnancy. If oral route fails → buccal/IM/IV route.

All HG / NVP requiring treatment

Thiamine 25–50mg TDS oral MANDATORY

RCOG mandates thiamine supplementation in ALL HG requiring antiemetics. Prevents Wernicke's encephalopathy. Continue throughout treatment period.

Full treatment ladder:

Step 1Lifestyle + ginger — Small, frequent carbohydrate-rich meals. Avoid triggers. Rest. Ginger 250mg QDS. P6 acupressure. Cold food (less smell). For mild NVP only.

Step 2First-line antiemetic (oral): Prochlorperazine 5–10mg TDS OR Cyclizine 50mg TDS OR Promethazine 25mg TDS. Add thiamine 25mg TDS. Review 24–48 hours.

Step 3Second-line antiemetic: Metoclopramide 10mg TDS (max 5 days — tardive dyskinesia risk) OR Ondansetron 4–8mg BD-TDS (RCOG: use with caution — small increased oral cleft risk in 1st trimester, benefit/risk discussion needed). Continue thiamine.

Step 4Combination antiemetics: Two antiemetics from different classes. Add H2 blocker (ranitidine 150mg BD or omeprazole 20mg OD) for reflux component. Prednisolone 40mg OD reducing over 2 weeks for refractory HG — secondary care initiation.

Step 5Hospital: IV management — IV 0.9% NaCl + KCl replacement (NOT 5% dextrose — precipitates Wernicke's). IV thiamine (Pabrinex 100mg BD for 3 days). IV ondansetron 4–8mg TDS. IV metoclopramide 10mg TDS. TPN (total parenteral nutrition) for refractory HG failing all measures — specialist decision.

NEVER give

5% dextrose (glucose) IV without thiamine — precipitates Wernicke's encephalopathy. IV thiamine BEFORE any glucose-containing fluids in patients with prolonged vomiting.

The evidence base for antiemetic safety in pregnancy is robust. Prochlorperazine, cyclizine, and promethazine have decades of use data and are RCOG Category A (no evidence of harm). The ondansetron controversy: a 2014 Danish cohort study suggested a small increased risk of oral clefts (absolute risk increase ~0.1%) — RCOG recommends discussing this with women but does not prohibit use, particularly after 10 weeks when palate closure is complete. The risk of undertreated HG (nutritional deficiency, IUGR, preterm birth, maternal psychological harm, fetal thiamine deficiency) substantially outweighs antiemetic risks. Metoclopramide: maximum 5-day courses due to extrapyramidal side effects — prescribe with clear instructions and a clear stop date.

Lifestyle

Non-Pharmacological Strategies & Supportive Measures

Done

Lifestyle modifications alone rarely control moderate-severe NVP but are valuable adjuncts. Emotional and practical support is as important as medication.

Eating pattern Small, frequent, carbohydrate-rich meals (plain crackers, toast, rice, bland foods). Eating before getting out of bed in the morning. Avoid large meals — gastric distension worsens nausea. Separate fluids from solids by 30 minutes.

Cold foods Cold or room-temperature foods produce less smell/steam than hot foods — significantly reduces nausea triggers in many women. Ice lollies, cold water, frozen ginger chews.

Trigger avoidance Identify individual triggers: strong smells (perfume, cooking, petrol), heat, stuffy environments, fatigue. Use fan in kitchen. Delegate cooking. Open windows. Rest is treatment not laziness.

Ginger Best-evidenced non-pharmacological treatment. Ginger tea, ginger biscuits, ginger capsules 250mg QDS. Reduces nausea scores by 30% in mild NVP. Not effective for severe HG.

Hydration strategy Sip cold water, ice chips, clear broth, diluted juice in small amounts frequently. Sports drinks replace electrolytes. IV fluids if oral hydration fails — do not delay seeking help.

Sick notes & workplace Proactively issue fit notes for women unable to work. HG is a legitimate medical condition. ACAS guidance: adjustments should include flexible hours, working from home, toilet access. Do not trivialise.

Psychological support Pregnancy Sickness Support helpline (0800 0 334 899). Online communities. CBT for health anxiety/anticipatory nausea. Screen with PHQ-9 — treat depression if identified. Partners need education too.

Vitamin supplements Continue folic acid (important for NTD prevention — do not stop). Switch to evening-only dosing if tablets worsen nausea. Pregnancy vitamins with iron may worsen nausea — trial without iron if needed.

Up to 30% of women with HG lose their jobs due to prolonged absence — GP-issued fit notes and workplace adjustment letters are clinical interventions that prevent long-term financial harm. Encouraging rest is not passive — sleep deprivation significantly amplifies nausea via cortisol elevation. Folic acid should continue through the first trimester despite nausea — the risk of NTD from cessation vastly outweighs the modest contribution of folic acid to nausea. Pregnancy Sickness Support charity (PSS) provides 24/7 helpline staffed by HG survivors and has been shown to reduce hospital admissions by providing real-time management guidance.

Safety

Follow-Up, Monitoring & Safety-Netting

Done

NVP is dynamic — patients can deteriorate quickly. Safety-netting must be explicit and documented. Most resolve by 16–20 weeks; post-20 week vomiting needs reinvestigation.

24–48 hours

Review response to first antiemetic. If no improvement: step up ladder, do not continue failing treatment. Reassess hydration. Weight if possible.

1 week

Ongoing moderate-severe NVP: recheck urine dipstick, weight, symptoms. If ketonuria worsening → hospital. If improving → continue and review at 2 weeks.

Regular monitoring

Weekly for all HG patients in primary care. Weight at every visit. PUQE score at every visit. Urine dipstick at every visit. Document clearly.

Resolution

Most NVP resolves by 16–20 weeks. Review medications for cessation. Some HG persists throughout pregnancy — ongoing management with obstetric team. Post-natal debriefing important for mental health.

Safety-net — same-day hospital

Not keeping any fluids down for 24h · Ketonuria +++ · Postural hypotension · New abdominal pain · Fever · Any neurological symptoms (confusion, double vision)

Safety-net — 999

Confusion + vomiting + eye movement abnormality → IV thiamine + 999 (Wernicke's encephalopathy) · Collapse, severe hypotension · Haematemesis

Post-16 weeks

New or worsening vomiting after 16 weeks → re-investigate: exclude UTI, reflux, appendicitis. If >20 weeks: exclude pre-eclampsia (BP, urine protein), AFLP (LFTs, coagulation).

RCOG Green-top 69 emphasises that treatment review at 24–48 hours is not optional — it is the safety mechanism that prevents the spiral of inadequate community treatment → acute hospital presentation. The most common error is continuing an antiemetic that is clearly not working for 2 weeks before stepping up. Acute fatty liver of pregnancy (AFLP) is a rare but life-threatening condition presenting with vomiting, jaundice, and coagulopathy at 28–40 weeks — mortality without prompt delivery is 50%. Any woman with persistent vomiting beyond 20 weeks and abnormal LFTs or jaundice must be referred immediately to secondary care.