What is the first-line antibiotic for urinary tract infections (UTI) in pregnancy?

First-Line Antibiotic for UTI in Pregnancy

For uncomplicated UTI in pregnancy, prescribe nitrofurantoin (100 mg twice daily for 5-7 days) or fosfomycin trometamol (3 g single dose) as first-line therapy, avoiding trimethoprim in the first trimester and trimethoprim-sulfamethoxazole in the last trimester. 1, 2

Recommended First-Line Agents

Nitrofurantoin

• Nitrofurantoin is the most established first-line option with over 35 years of safe use in pregnancy, including for asymptomatic bacteriuria 3
• Dosing: 100 mg twice daily for 5-7 days 1, 2
• Alternative formulation: macrocrystals 50-100 mg four times daily for 5 days 1
• Maintains favorable resistance profiles globally and lacks R-factor resistance development 3
• Demonstrates high efficacy with cure rates comparable to fosfomycin 4

Fosfomycin Trometamol

• Single-dose fosfomycin (3 g) is equally effective and safe for uncomplicated UTI and asymptomatic bacteriuria in pregnancy 4
• Provides excellent compliance due to single-dose administration 1, 2
• No significant differences in clinical cure rates (RR 0.95) or microbiological cure rates (RR 0.96) compared to nitrofurantoin 4
• Maintains favorable global resistance patterns 1

Third-Generation Cephalosporins

• Cefixime is a rational alternative due to high E. coli sensitivity, safety profile, and compliance in pregnant women 2
• Consider when first-line agents are contraindicated or unavailable 2

Critical Trimester-Specific Restrictions

Avoid These Agents

• Trimethoprim: contraindicated in first trimester due to folate antagonism and teratogenic concerns 1
• Trimethoprim-sulfamethoxazole: contraindicated in last trimester due to risk of neonatal hyperbilirubinemia and kernicterus 1
• Fluoroquinolones should not be used as first-line therapy 1
• Beta-lactams (except third-generation cephalosporins) should not be used as first-line empirical therapy 1

Treatment Duration Considerations

• Pregnant women require longer treatment courses than non-pregnant women for uncomplicated UTI 2, 5
• Three-day therapy with amoxicillin 500 mg three times daily is an alternative for symptomatic UTI, though less preferred than nitrofurantoin or fosfomycin 5
• Single-dose therapy shows approximately 80% cure rates but may be less reliable than multi-day regimens 5

Essential Follow-Up

• Obtain urine culture 7 days after treatment completion to confirm cure, as treatment failure carries significant maternal and fetal risks 5
• Urine culture is mandatory in pregnancy for suspected pyelonephritis, persistent symptoms, or recurrence within 4 weeks 1
• Do not perform routine post-treatment cultures in asymptomatic patients after documented cure 1

Prophylaxis for Recurrent UTI in Pregnancy

• For pregnant women with recurrent UTI history, postcoital prophylaxis is highly effective using either cephalexin 250 mg or nitrofurantoin 50 mg as a single dose after intercourse 6
• This approach reduced UTI incidence from 130 infections pre-prophylaxis to only 1 infection during pregnancy (highly significant reduction) 6

Common Pitfalls to Avoid

• Never treat asymptomatic bacteriuria without symptoms except in pregnancy, where treatment is indicated 7
• Do not use fluoroquinolones as first-line agents despite their efficacy in non-pregnant populations 1
• Avoid single-dose therapy for symptomatic UTI in pregnancy; multi-day regimens provide better cure rates 5
• Do not prescribe empirical antibiotics without considering local resistance patterns (should be <20% for lower UTI) 1