What is the recommended treatment for a urinary tract infection (UTI) in pregnancy?

Treatment of Urinary Tract Infection in Pregnancy

Nitrofurantoin 100 mg orally four times daily for 5-7 days is the recommended first-line treatment for urinary tract infections in pregnant women, with cephalexin 500 mg orally four times daily for 7-14 days as an alternative option. 1

Diagnostic Approach Before Treatment

• Always obtain a urine culture before initiating antibiotics to guide antibiotic selection and confirm diagnosis 1
• Screen for asymptomatic bacteriuria at least twice during pregnancy, with optimal timing at 12-16 weeks of gestation 1
• This screening is critical because untreated bacteriuria increases pyelonephritis risk to 20-37% compared to only 1-4% in treated women 1

First-Line Antibiotic Regimens

For uncomplicated cystitis and asymptomatic bacteriuria:

• Nitrofurantoin 100 mg orally four times daily for 5-7 days is the preferred first-line agent 1, 2

  • Safe throughout pregnancy except avoid near term due to risk of hemolytic anemia in the newborn 2
  • Achieves high bactericidal concentrations in urinary tract with minimal resistance development 3

• Cephalexin 500 mg orally four times daily for 7-14 days as an alternative 1

  • Particularly useful when resistance to other agents is suspected 2

• Fosfomycin 3 g single dose specifically for uncomplicated cystitis 1, 2

  • Convenient single-dose administration improves compliance 2
  • Equally effective as multi-day regimens for uncomplicated cystitis 2, 4

Treatment Duration

• Minimum 4-7 days for symptomatic UTI and asymptomatic bacteriuria 1, 2
• A 7-14 day course ensures complete eradication, particularly with cephalosporins 1
• Shorter courses (1-3 days) are not recommended in pregnancy 2

Post-Treatment Monitoring

• Repeat urine culture 1-2 weeks after completing treatment to confirm microbiological cure 1
• This step is essential—failure to confirm cure leads to missed persistent infections that increase pyelonephritis risk 1

Special Clinical Scenarios

Pyelonephritis or severe infections:

• Requires initial parenteral therapy and hospitalization given significant maternal and fetal risks 1

Group B Streptococcus bacteriuria:

• Treat immediately at any concentration when detected 1
• This differs from other organisms where colony count thresholds apply 1

Recurrent UTIs:

• Daily low-dose prophylactic antibiotics (nitrofurantoin 50 mg or cephalexin 250 mg postcoitally) can prevent recurrences 2, 3

Antibiotics to Avoid

• Trimethoprim-sulfamethoxazole is contraindicated:

  • First trimester: neural tube defect risk 1, 2
  • Third trimester: kernicterus/neonatal hyperbilirubinemia risk 1, 2

• Fluoroquinolones should be avoided throughout pregnancy due to concerns about cartilage development 1, 2

• Ampicillin is no longer recommended due to high resistance rates 5

Critical Pitfalls to Avoid

• Never treat without obtaining urine culture for susceptibility testing 1
• Do not use antibiotics that don't achieve adequate urinary concentrations 2
• Always confirm microbiological cure with repeat culture—this prevents progression to pyelonephritis 1
• Remember that asymptomatic bacteriuria requires treatment in pregnancy (unlike non-pregnant populations) 2