What is the preferred antibiotic for urinary tract infections (UTIs) in pregnant women?

Preferred Antibiotics for UTIs in Pregnant Women

For urinary tract infections in pregnant women, nitrofurantoin, cephalexin (or other cephalosporins), and fosfomycin are the preferred first-line antibiotics, with nitrofurantoin being the most commonly prescribed and generally preferred option. 1, 2

First-Line Treatment Options

• Nitrofurantoin: 100mg twice daily for 5-7 days

  • Most frequently prescribed antibiotic for UTIs in pregnancy 2
  • Effective against most common uropathogens
  • Note: Should be used with caution in the first trimester due to potential risk for birth defects 2

• Cephalexin: Appropriate dosing based on infection severity

  • Safe throughout pregnancy
  • Good option when nitrofurantoin is contraindicated

• Fosfomycin: 3g single dose

  • Convenient single-dose treatment
  • Effective against common uropathogens including some resistant strains

Treatment Algorithm Based on Clinical Presentation

1. Asymptomatic Bacteriuria

• Screen in first trimester with urine culture 1
• If positive, treat with short course of antibiotics:
  • Nitrofurantoin 100mg BID for 5 days OR
  • Fosfomycin 3g single dose OR
  • Cephalexin appropriate dose for 3-5 days
• Follow-up urine culture 1 week after treatment to confirm cure

2. Uncomplicated Cystitis

• Nitrofurantoin 100mg BID for 5 days (first choice)
• Cephalexin for 5-7 days (alternative)
• Fosfomycin 3g single dose (alternative)

3. Pyelonephritis

• Requires hospitalization and IV antibiotics:
  • Ceftriaxone or other third-generation cephalosporins
  • Amoxicillin with aminoglycoside
  • Carbapenems for severe cases or resistant organisms 1

Important Considerations

• Antibiotic resistance: Local resistance patterns should guide empiric therapy
• Trimethoprim-sulfamethoxazole: Generally avoided in first trimester due to potential teratogenic effects and near term due to risk of neonatal hyperbilirubinemia 2, 1
• Fluoroquinolones: Contraindicated during pregnancy due to potential effects on fetal cartilage development 3
• Beta-lactams: Generally safe in pregnancy but may have variable efficacy against some uropathogens 1

Follow-up and Prevention

• Obtain follow-up urine culture 1-2 weeks after treatment completion
• For recurrent UTIs, consider prophylactic antibiotics after consultation with specialists
• Recommend increased fluid intake and frequent urination as preventive measures

Cautions and Pitfalls

• Untreated UTIs in pregnancy can lead to serious complications including pyelonephritis, preterm labor, low birth weight, and sepsis 2, 1
• Always obtain urine culture before initiating treatment to guide therapy
• Consider the possibility of early pregnancy when treating women of reproductive age with UTIs 2
• Avoid empiric use of antibiotics without susceptibility testing when possible

Recent evidence suggests that short-course therapy (3-5 days) may be as effective as longer courses for uncomplicated UTIs, even in pregnancy, potentially reducing antibiotic exposure 1, 4.