What is the recommended treatment for a Urinary Tract Infection (UTI) in a pregnant woman during her first trimester?

First Trimester UTI Treatment in Pregnancy

For symptomatic UTIs in the first trimester of pregnancy, nitrofurantoin is the first-line antibiotic, with cephalosporins (cephalexin, cefpodoxime, or cefuroxime) as appropriate alternatives, while trimethoprim-sulfamethoxazole should be avoided due to teratogenic risks. 1

First-Line Antibiotic Selection

Preferred Agents

• Nitrofurantoin is recommended as the first-line treatment for first trimester UTIs 1
• Fosfomycin (single 3g dose) serves as an acceptable alternative 1
• Cephalosporins (cephalexin 500mg four times daily, cefpodoxime, or cefuroxime) are appropriate options with excellent safety profiles 1

Agents to Avoid

• Trimethoprim and trimethoprim-sulfamethoxazole must be avoided in the first trimester due to potential teratogenic effects including anencephaly, heart defects, and orofacial clefts 1, 2
• Fluoroquinolones should be avoided throughout all trimesters of pregnancy 1

Treatment Duration and Monitoring

Course Length

• Treat for 7-14 days to ensure complete eradication of infection 1
• Shorter courses have insufficient evidence in pregnancy, making 7-14 days the standard recommendation 1

Diagnostic Approach

• Obtain urine culture before initiating treatment to guide antibiotic selection and confirm diagnosis 1
• The sensitivity of routine urinalysis is only 50% for identifying bacteriuria, making culture essential 1
• Follow-up urine culture 1-2 weeks after completing treatment is recommended to confirm cure 1

Critical Clinical Context

Why Treatment Cannot Be Delayed

• Untreated bacteriuria increases pyelonephritis risk 20-30 fold (from 1-4% with treatment to 20-35% without) 1
• Treatment reduces premature delivery and low birth weight infants 1
• Delaying treatment increases risk of adverse pregnancy outcomes 1

Special Considerations for Penicillin Allergy

• Despite theoretical cross-reactivity, only 10% of penicillin-allergic patients react to cephalosporins 1
• Assess anaphylaxis risk; if low, cephalosporins remain safe options 1
• If true severe allergy exists, fosfomycin or nitrofurantoin are alternatives 1

Important Caveats

When NOT to Use Nitrofurantoin

• Do not use nitrofurantoin for suspected pyelonephritis as it does not achieve therapeutic blood concentrations 1
• For severe infections or pyelonephritis, initial parenteral cephalosporins or other agents achieving adequate blood levels are required 1

Group B Streptococcus (GBS)

• GBS bacteriuria at any concentration requires treatment at diagnosis AND intrapartum prophylaxis during labor 1
• This represents heavy genital tract colonization requiring dual intervention 1

Asymptomatic Bacteriuria

• Always treat asymptomatic bacteriuria in pregnancy (unlike non-pregnant women) to prevent progression to pyelonephritis 1
• Screen ideally at 12-16 weeks gestation with urine culture 1