What is the recommended management for asymptomatic bacteriuria (presence of bacteria in urine) in pregnancy?

Management of Asymptomatic Bacteriuria in Pregnancy

All pregnant women should be screened for asymptomatic bacteriuria with urine culture at least once in early pregnancy (optimally at 12-16 weeks gestation) and treated with antibiotics if positive to prevent pyelonephritis and adverse pregnancy outcomes. 1

Diagnosis

• Diagnosis must be based on urine culture, which is the gold standard 2, 1
• Bacteriuria is defined as:
  • 2 consecutive voided urine specimens with isolation of the same bacterial strain in quantitative counts ≥10^5 CFU/mL, OR
  • A single catheterized urine specimen with 1 bacterial species isolated in a quantitative count ≥10^2 CFU/mL 2, 1
• Urine dipstick testing for pyuria has low sensitivity (approximately 50%) and is not recommended as a reliable screening method 1, 3
• Dipslide culture methods may be a cost-effective alternative to traditional urine culture in resource-limited settings 3, 4

Treatment

• A 3-7 day course of antibiotics is recommended based on culture and sensitivity results 2, 1
• First-line antibiotic options include:
  • Nitrofurantoin 100mg BID (appears to be the antibiotic of choice) 1, 3
  • Cephalexin 500mg QID
  • Ampicillin 500mg QID (if susceptible) 1
• Avoid fluoroquinolones, tetracyclines, and trimethoprim-sulfamethoxazole in the first and third trimesters 1
• A 7-day regimen provides better microbiological cure rates compared to single-dose therapy 1, 5

Follow-up

• Obtain follow-up urine culture 1-2 weeks after completing therapy to ensure clearance of bacteriuria 1
• Periodic screening for recurrent bacteriuria should be undertaken following therapy 2, 1
• If bacteriuria persists, retreatment with a different antibiotic based on susceptibility is recommended 1

Clinical Significance

• Untreated asymptomatic bacteriuria in pregnancy carries a 20-30 fold increased risk of developing pyelonephritis compared to women without bacteriuria 1
• Treatment decreases the risk of:
  • Pyelonephritis from 20-35% to 1-4% 1, 6
  • Low birth weight infants 1, 5, 6
  • Preterm delivery 1, 6
• Screening and treatment programs have demonstrated significant reductions in pyelonephritis rates, from 1.8% to 0.6% and from 2.1% to 0.5% in different healthcare centers 1

Common Pitfalls to Avoid

• Inadequate screening (using only dipstick instead of culture)
• Insufficient treatment duration (single-dose therapy is less effective than multi-day regimens)
• Inappropriate antibiotic selection (not based on susceptibility testing)
• Failure to follow up with post-treatment cultures
• Overtreatment of contaminated specimens 1

The evidence strongly supports screening and treatment of asymptomatic bacteriuria in pregnancy as an effective strategy to reduce significant maternal and fetal complications.