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

Treatment of Urinary Tract Infections During Pregnancy

First-line treatment for UTIs in pregnancy includes nitrofurantoin, fosfomycin, and beta-lactams, with nitrofurantoin being preferred due to its safety profile and minimal impact on vaginal and fecal flora. 1

Screening and Diagnosis

• All pregnant women should be screened for bacteriuria by urine culture at least once in early pregnancy (typically at 12-16 weeks) 2
• Any quantity of GBS bacteriuria during pregnancy requires treatment and is a marker for heavy genital tract colonization 2
• Catheterized urinalysis provides more reliable results than clean-catch specimens 1
• Screening for pyuria alone has low sensitivity (only ~50%) for identifying bacteriuria in pregnant women 2

Treatment Algorithm for UTIs in Pregnancy

For Asymptomatic Bacteriuria:

1. Must be treated in pregnant women to prevent pyelonephritis and adverse pregnancy outcomes 1
2. Preferred agents:
   • Nitrofurantoin 100mg BID for 5-7 days
   • Fosfomycin 3g single dose (although it has limited clinical evaluation in pregnancy) 1
   • Beta-lactams (amoxicillin, cephalosporins) 3

For Symptomatic UTIs:

1. First-line options:

   • Nitrofurantoin 100mg BID for 5-7 days (avoid in G6PD deficiency)
   • Amoxicillin 500mg TID for 3-7 days 4
   • Cephalosporins (cefuroxime, cephradine) 5

2. Important considerations:

   • TMP-SMX should be avoided in the first and third trimesters 1, 3
   • Fluoroquinolones and tetracyclines should be avoided throughout pregnancy 3

Duration of Treatment

• The optimal duration of antimicrobial therapy for bacteriuria in pregnant women has not been definitively determined 2
• Options include:
  • 3-7 day regimens for uncomplicated cystitis
  • Single-dose therapy with fosfomycin
  • Continuous antimicrobial therapy until delivery (historical approach) 2

Follow-up and Monitoring

• Urine culture should be repeated 1-2 weeks after completing treatment to confirm cure 1
• If bacteriuria persists or recurs, retreatment with a different antibiotic based on susceptibility testing is recommended
• For recurrent UTIs, prophylactic antibiotics may be considered after initial treatment

Complications and Prevention

• Untreated UTIs in pregnancy can lead to pyelonephritis, preterm birth, low birth weight, and spontaneous abortion 3, 6
• Treatment of asymptomatic bacteriuria decreases rates of pyelonephritis from 20-37% to 1-6% 2
• Preventive measures include:
  • Increased fluid intake
  • Urinating before and after sexual activity
  • Proper wiping technique (front to back)
  • Avoiding irritating feminine products 1

Special Considerations

• Physiologic changes in pregnancy (increased GFR, total body volume, enhanced cardiac output) may affect antibiotic pharmacokinetics 3
• For pyelonephritis, hospitalization and initial IV antibiotics are recommended, with transition to oral therapy once clinically improved 1
• GBS bacteriuria at any concentration requires treatment during pregnancy and intrapartum prophylaxis during delivery 2

Common Pitfalls to Avoid

1. Failing to screen for asymptomatic bacteriuria in early pregnancy
2. Using TMP-SMX in first or third trimester
3. Using fluoroquinolones or tetracyclines at any point during pregnancy
4. Not confirming cure with follow-up urine culture
5. Overlooking GBS bacteriuria, which requires specific management

While multiple antibiotic regimens have shown efficacy, nitrofurantoin and beta-lactams have the most established safety profile in pregnancy, making them preferred first-line options for most uncomplicated UTIs.