Do you treat asymptomatic bacteriuria (ASB) in pregnancy?

Treatment of Asymptomatic Bacteriuria in Pregnancy

Yes, asymptomatic bacteriuria (ASB) in pregnancy should be treated with antibiotics to prevent serious maternal and fetal complications. This recommendation is based on strong evidence showing significant reduction in pyelonephritis, preterm birth, and low birth weight infants when ASB is treated during pregnancy.

Rationale for Treatment

• Pregnant women with untreated ASB have a 20-30 fold increased risk of developing pyelonephritis compared to women without bacteriuria 1
• Treatment of ASB during pregnancy decreases the risk of:
  • Pyelonephritis from 20-35% to 1-4% 1
  • Low birth weight infants 1, 2
  • Preterm delivery 1, 2

Screening Recommendations

• All pregnant women should be screened for ASB with urine culture at least once early in pregnancy 1
• Optimal timing: Collect urine culture at one of the initial prenatal visits, typically around 12-16 weeks gestation 1
• Urine culture is the gold standard for diagnosis; dipstick testing for pyuria has low sensitivity (approximately 50%) 1, 3

Treatment Protocol

1. Antibiotic Selection:

   • Choose antibiotics based on culture and sensitivity results when available
   • Nitrofurantoin is often the preferred first-line agent in pregnancy 3
   • Other options include beta-lactams (ampicillin, cephalexin) and fosfomycin
   • Avoid trimethoprim-sulfamethoxazole in first trimester (risk of neural tube defects) and third trimester (risk of kernicterus) 4
   • Avoid fluoroquinolones and tetracyclines throughout pregnancy 4

2. Treatment Duration:

   • IDSA recommends 4-7 days of antimicrobial treatment rather than shorter durations 1
   • Seven-day regimens provide better microbiological cure rates than single-dose therapy 3
   • The optimal duration varies depending on the specific antimicrobial used 1

Follow-up

• Consider follow-up urine culture after completion of therapy to confirm clearance of bacteriuria
• There is insufficient evidence to recommend for or against repeat screening during pregnancy following an initial negative culture or after treatment of an initial episode of ASB 1

Clinical Impact of Treatment

Implementation of screening and treatment programs for ASB in pregnant women has demonstrated significant reductions in pyelonephritis rates:

• From 1.8% to 0.6% in a Spanish healthcare center 1
• From 2.1% to 0.5% in a Turkish healthcare center 1

Common Pitfalls to Avoid

1. Inadequate screening: Relying on dipstick testing alone instead of urine culture
2. Insufficient treatment duration: Using single-dose therapy which has lower microbiological cure rates
3. Inappropriate antibiotic selection: Using antibiotics contraindicated in pregnancy
4. Failure to follow up: Not confirming clearance of bacteriuria after treatment
5. Overtreatment: Treating asymptomatic bacteriuria in non-pregnant populations (diabetic women, elderly) where treatment has not shown benefit 1

The evidence strongly supports screening and treatment of ASB in pregnancy as a standard of care to prevent serious maternal and fetal complications, despite some limitations in the quality of older studies 2.