What are the best management options for a pregnant woman experiencing vomiting?

Management of Vomiting in Pregnancy

Start with vitamin B6 (pyridoxine) 10-25 mg every 8 hours as first-line pharmacologic treatment, adding doxylamine if symptoms persist, and escalate systematically through antihistamines, metoclopramide, ondansetron, and finally corticosteroids only for severe refractory cases. 1, 2

Initial Assessment and Severity Stratification

• Evaluate severity using the Motherisk Pregnancy-Unique Quantification of Emesis (PUQE) score: mild (≤6), moderate (7-12), and severe (≥13) 1, 2
• Check for signs of hyperemesis gravidarum: weight loss >5% of pre-pregnancy weight, dehydration, ketonuria, and electrolyte imbalances 1, 2
• Obtain electrolyte panel, liver function tests (40-50% of hyperemesis patients have elevated AST/ALT), and urinalysis for ketonuria 2
• Perform abdominal ultrasound to rule out multiple or molar pregnancies and hepatobiliary causes 2

Stepwise Treatment Algorithm

Mild Symptoms (PUQE ≤6)

Dietary and Lifestyle Modifications:

• Small, frequent, bland meals following the BRAT diet (bananas, rice, applesauce, toast) 1, 3
• High-protein, low-fat meals with avoidance of spicy, fatty, acidic, and fried foods 1, 3
• Identify and avoid specific food triggers and strong odors 1, 3
• Separate solid and liquid intake to reduce gastric distension 3

First-Line Pharmacologic Treatment:

• Vitamin B6 (pyridoxine) 10-25 mg every 8 hours 1, 2
• Ginger 250 mg capsules 4 times daily as alternative non-pharmacologic option 1, 3

Moderate Symptoms (PUQE 7-12)

Combination Therapy:

• Add doxylamine to vitamin B6 if symptoms persist despite B6 alone 1, 2
• Use combination products: doxylamine/pyridoxine 10 mg/10 mg or 20 mg/20 mg 1, 2
• The American College of Obstetricians and Gynecologists recommends doxylamine-pyridoxine as the preferred initial antiemetic throughout pregnancy and breastfeeding 2

Alternative First-Line Agents:

• Other antihistamines (promethazine, cyclizine) or phenothiazines (prochlorperazine, chlorpromazine) share similar safety profiles 2

Severe Symptoms or Treatment Failure

Second-Line Therapy:

• Metoclopramide 5-10 mg orally every 6-8 hours is the preferred second-line agent when first-line antihistamines fail, with less drowsiness and fewer discontinuations compared to promethazine 2
• No increased risk of major congenital defects found in meta-analysis of 33,000 first-trimester exposures 2
• Withdraw immediately if extrapyramidal symptoms develop 2

Ondansetron as Alternative Second-Line:

• Reserve ondansetron as second-line therapy due to concerns about congenital heart defects when used before 10 weeks gestation, though recent data suggest the risk is low 2
• The American College of Obstetricians and Gynecologists recommends using ondansetron on a case-by-case basis before 10 weeks of pregnancy 2
• Compatible throughout pregnancy and breastfeeding 2

Hyperemesis Gravidarum (Severe Refractory Cases)

Hospitalization Criteria:

• Frequent vomiting (≥5-7 episodes daily) despite maximal antiemetics 2
• Progressive weight loss ≥5% of pre-pregnancy weight 2
• Inability to maintain oral intake of 1000 kcal/day for several days 2
• Electrolyte imbalances or ketonuria 2

Immediate Interventions:

• Intravenous fluid resuscitation targeting urine output of at least 1 L/day 2
• Electrolyte replacement with particular attention to potassium and magnesium to prevent cardiac arrhythmias 2
• Thiamine 200-300 mg IV daily for at least 3-5 days to prevent Wernicke's encephalopathy, then switch to oral maintenance (50-100 mg daily) once vomiting is controlled 2
• For suspected Wernicke's encephalopathy: thiamine 500 mg IV three times daily (1,500 mg total daily dose) 2

Third-Line Therapy (Last Resort):

• Methylprednisolone 16 mg IV every 8 hours for up to 3 days, then taper over 2 weeks to lowest effective dose, maximum duration 6 weeks 2
• Use with caution in first trimester due to slight increased risk of cleft palate when given before 10 weeks gestation 2
• Reduces rehospitalization rates in severe refractory cases 2

Enteral Feeding Considerations:

• Reserve nasojejunal feeding (preferred over nasogastric) for patients who have failed maximal medical therapy and cannot maintain adequate nutrition 2
• Consider before escalating to total parenteral nutrition 2

Critical Monitoring Parameters

For All Patients:

• Regular assessment of hydration status, weight trajectory, and symptom severity using PUQE score 1, 2
• Monitor for resolution of ketonuria as objective marker of adequate rehydration 2

For Hospitalized Patients:

• Daily monitoring of body weight, urine output, electrolytes, and renal function until stable 2
• Check BUN/creatinine ratio and venous blood gas for metabolic alkalosis 2
• Perform electrocardiography to assess QT interval, as hypokalemia with or without hypomagnesemia prolongs QT and increases risk of ventricular arrhythmias 2
• Monitor liver function tests, as approximately 50% of hyperemesis patients have abnormal AST and ALT 2

Thiamine Monitoring:

• Check thiamine status (RBC or whole blood thiamine diphosphate) every trimester in all hyperemesis patients, particularly those with inadequate weight gain 2

Expected Timeline and Prognosis

• Nausea and vomiting typically begins at 4-6 weeks, peaks at 8-12 weeks, and subsides by week 20 of pregnancy 1, 3
• Hyperemesis typically resolves by week 16-20 in 80% of cases, though 10% may experience symptoms throughout pregnancy 2
• Early intervention is crucial as it may prevent progression to hyperemesis gravidarum 1, 2

Critical Pitfalls to Avoid

• Do not skip the stepwise approach and jump directly to advanced therapies like corticosteroids or olanzapine, as this violates evidence-based guidelines 2
• Do not use PRN or intermittent dosing in refractory cases; switch to around-the-clock scheduled antiemetic administration 2
• Do not tell patients to "drink more water" as hypotonic fluids can worsen fluid losses; use glucose-electrolyte oral rehydration solutions when oral intake resumes 2
• Do not withhold thiamine supplementation in patients with prolonged vomiting, as thiamine reserves can be completely exhausted after only 20 days of inadequate oral intake 2
• Avoid drugs that prolong QT interval (proton-pump inhibitors, macrolides, fluoroquinolones) in patients with electrolyte abnormalities 2
• Do not routinely treat biochemical hyperthyroidism in hyperemesis patients, as it is self-limited and resolves as the condition improves 2

Special Considerations

• Pregnancy itself increases thiamine requirements, and hyperemesis rapidly depletes thiamine stores within 7-8 weeks of persistent vomiting 2
• For patients with adjustable gastric bands, deflation may be necessary to prevent band slippage and nutrient deficiencies 2, 3
• Multidisciplinary involvement (maternal-fetal medicine, gastroenterology, nutrition services, mental health professionals) is recommended for severe refractory cases, preferably at tertiary care centers 2
• Mental health support is important as anxiety and depression are common with severe hyperemesis 2
• Recurrence risk is high (40-92%) in subsequent pregnancies 2