Vomiting in pregnancy

Nausea and vomiting affect 60–70% of pregnant women; persistent, severe vomiting (hyperemesis gravidarum) occurs in 1–2%. Hyperemesis is a common reason for hospital admission in the first and second trimesters, averaging around five days.

Managing it early may reduce the eventual severity.

History

Check the timing fits the expected pattern — hyperemesis usually begins 4–7 weeks, peaks at 9 weeks, and has resolved in 90% by 16–20 weeks. Assess fluid/food intake, weight loss, urine output, treatments already tried, and medical/medication/allergy history.

Score severity with the Pregnancy-Unique Quantification of Emesis (PUQE) tool — all four major guidelines (SOMANZ, RCOG, SOGC, ACOG) recommend it, and it is what triages a woman to community or hospital management.

Symptoms suggesting another cause: intercurrent infection (UTI, gastroenteritis), gallstones, diabetes, hyperthyroidism; abdominal pain, fever, neurological symptoms or hypertension also suggest an alternative diagnosis.

Examination

Assess dehydration: mucous membranes, peripheral circulation, postural hypotension (a systolic drop of more than 20 mmHg or diastolic drop of more than 10 mmHg), skin turgor, tachycardia, weight, temperature, blood pressure — plus a general exam directed at other possible causes from the history. Check social history; exclude difficult social situations (including domestic violence) in recurrent presentations.

Investigations

Urinary ketones on dipstick: 1+ or less, try oral antiemetics; 2+ or more, IV rehydration is recommended. Also: MSU (UTI is often asymptomatic in pregnancy), FBC/electrolytes/creatinine, TSH.

Mild–moderate symptoms

Nausea with or without vomiting, no or moderate dehydration, likely to respond to community-based fluids and antiemetics.

Non-pharmacological:

• Small, frequent fluids, taken separately from meals; cold or frozen drinks and foods are often better tolerated.
• Small frequent high-carbohydrate, low-fat meals; avoid fatty, spicy, fried and battered food.
• High-protein snacks between meals; avoid an empty stomach.
• Crackers or plain biscuits before getting out of bed, and get up slowly.
• Avoid trigger smells and foods; rest, since fatigue worsens nausea.
• Switch to an iron-free multivitamin if there is no iron-deficiency anaemia (restart around 12 weeks, when iron demand rises).
• Ginger, 1–2 g of powdered ginger daily (AJGP’s guideline comparison cites 250 mg four times daily) — the complementary therapy all four guidelines endorse.
• Wrist acupressure (no evidence of harm, limited evidence of benefit) and acupuncture.

Pharmacological (if non-pharmacological measures fail after 1 week): pyridoxine 12.5 mg morning and midday plus 25 mg at night, with doxylamine 25 mg at night (category A), increasing as tolerated to 12.5 mg morning/midday and 25 mg at night.

This combination is first-line in all four major guidelines, and is considerably more effective than pyridoxine alone. Doxylamine is sold in Australia as Restavit and Dozile — marketed as sleep aids, but first line for NVP. Ask the pharmacist for a scored tablet so it can be halved. The “do not take if pregnant” warning on some doxylamine packaging is not evidence-based.

If nausea and vomiting persist, add metoclopramide 10 mg three times daily (category A), or prochlorperazine 5–10 mg three to four times daily (category C), or promethazine 10–25 mg three to four times daily (category C). Metoclopramide is safe, effective and cheap, and is the usual second-line agent.

Ondansetron 4–8 mg two to three times daily (category B1) is best kept as adjunctive therapy for severe cases: because of the congenital malformation signal it is used second line, ideally after the first trimester and with counselling.

Review in 2–3 days, or sooner if needed. If symptoms persist, manage as severe or persistent hyperemesis.

Severe or persistent hyperemesis

Not responding to community fluids and antiemetics, and/or more than 5% weight loss, and/or biochemical abnormalities. Manage as for mild–moderate, plus:

• Consider referral.
• Arrange an ultrasound if not already done, to check for multiple or molar pregnancy.
• FBC, creatinine, LFTs, electrolytes — LFTs are abnormal in 50% of hospitalised patients (discuss if ALT is above 50) and resolve quickly once vomiting settles; refer to delivery suite if electrolyte abnormalities are significant.
• Check TFTs — abnormal in two-thirds of patients; an asymptomatic suppressed TSH with normal FT4/FT3 is subclinical hyperthyroidism.
• Give thiamine, because prolonged vomiting causes micronutrient deficiency and, rarely, Wernicke’s encephalopathy.
• For patients unable to tolerate or not responding to oral drugs (including ondansetron wafers), use a parenteral route: metoclopramide (category A) 10 mg IM/IV 8-hourly; ondansetron (category B1) 4–8 mg IV 8–12-hourly; prochlorperazine (category C) 12.5 mg IM or slow IV 8-hourly; promethazine (category C) 12.5–25 mg IM 4–6-hourly.

Refractory disease: SOMANZ and RCOG recommend adding corticosteroids once IV fluids and regular antiemetics have failed. The Cochrane review found no difference in days of admission versus placebo but a decreased readmission rate.

Temper expectations about any of these drugs. Cochrane’s review of 25 trials found the evidence for most comparisons to be of low or very low quality, with little high-quality or consistent evidence supporting any one intervention over another.