Do asymptomatic urinary tract infections (UTIs) in pregnancy require treatment?

Treatment of Asymptomatic UTI in Pregnancy is Essential

Pregnant women with asymptomatic bacteriuria should be screened for and treated with antibiotics to prevent serious maternal and fetal complications. 1

Rationale for Treatment

Asymptomatic bacteriuria (ASB) in pregnancy requires treatment due to significant risks if left untreated:

• Untreated ASB increases risk of pyelonephritis 20-30 fold during pregnancy 1
• Treatment reduces pyelonephritis incidence from 20-35% to 1-4% 1
• Treatment may reduce risk of:
  • Preterm birth (from 53 per 1000 to approximately 14 per 1000) 1
  • Low birth weight (from 137 per 1000 to 88 per 1000) 1

While a 2015 Dutch study suggested non-treatment might be acceptable for selected low-risk women (with pyelonephritis rates of only 2.4% in untreated women), this finding has limited generalizability as it enrolled only low-risk women and used only a single urine culture for diagnosis 1.

Screening and Diagnosis

• Screen all pregnant women with urine culture at one of the initial prenatal visits early in pregnancy 1
• ASB is defined as ≥105 CFU/mL of the same bacterial species in a urine specimen without symptoms of UTI
• ASB occurs in 2-7% of pregnant women 1, 2

Treatment Recommendations

Duration of Therapy

• 4-7 days of antimicrobial treatment is recommended rather than single-dose therapy 1
• Seven-day therapy is more effective than single-dose in preventing adverse outcomes like low birth weight 1

Antimicrobial Selection

First-line options (based on susceptibility testing):

• Nitrofurantoin (safe in pregnancy except near term)
• β-lactams (ampicillin or cephalexin)
• Fosfomycin (single dose may be effective for bacterial clearance, but has limited clinical evaluation in pregnancy) 1, 3

Important Considerations

• Avoid fluoroquinolones and tetracyclines during pregnancy due to potential fetal risks 4
• Use sulfonamides with caution in first trimester due to potential birth defect risks 5
• The 2011 American College of Obstetricians and Gynecologists recommended that sulfonamides and nitrofurantoin be used in first trimester only when other antimicrobials are clinically inappropriate 5

Follow-up

• Perform follow-up urine culture after treatment completion to confirm cure
• There is insufficient evidence to recommend for or against repeat screening during pregnancy for women with initial negative screening or after treatment of an initial episode 1

Clinical Pitfalls to Avoid

1. Don't dismiss ASB in pregnancy - unlike in non-pregnant women, ASB requires treatment during pregnancy
2. Don't use single-dose therapy - shorter courses have lower cure rates in pregnancy
3. Don't forget follow-up cultures - ensure bacteriuria has cleared after treatment
4. Don't overlook antimicrobial resistance - base treatment on susceptibility testing when available
5. Don't use potentially harmful antibiotics - consider fetal safety when selecting antimicrobials

The strong recommendation for screening and treatment of ASB in pregnancy is supported by multiple guidelines and decades of evidence showing significant reduction in serious maternal and fetal complications 1, 2.