How should a pregnant woman with dysuria, frequency, urgency, suprapubic or flank pain be evaluated and treated for a urinary tract infection?

Urinary Tract Infection in Pregnancy: Evaluation and Treatment

Immediate Diagnostic Approach

All pregnant women presenting with dysuria, frequency, urgency, suprapubic pain, or flank pain should have a urine culture with antimicrobial susceptibility testing obtained before initiating antibiotics, and empiric treatment should be started immediately without waiting for culture results. 1, 2

Clinical Presentation Recognition

• Lower UTI (Cystitis): Dysuria is the cardinal symptom with 90% accuracy for UTI when accompanied by frequency, urgency, or suprapubic pain in the absence of vaginal discharge 1, 3
• Upper UTI (Pyelonephritis): Fever >38°C, flank pain or costovertebral angle tenderness, with or without lower tract symptoms; systemic symptoms include chills, nausea, vomiting 1, 2
• Critical distinction: Up to 20% of pyelonephritis cases lack lower urinary symptoms, so isolated fever with flank pain warrants full evaluation 2

Laboratory Evaluation

Urinalysis with dipstick testing should be performed, but treatment decisions must not rely solely on urinalysis results 1

• Leukocyte esterase has 100% sensitivity but only 24.6% specificity and 32.8% positive predictive value in pregnancy 3
• Nitrite testing has 80.9% sensitivity but only 57.9% specificity and 41.4% positive predictive value in pregnancy 3
• Urine culture is mandatory in all pregnant women with suspected UTI to confirm diagnosis and guide therapy 1, 2, 4
• Blood cultures should be obtained if the patient appears systemically ill, has high fever, or has suspected pyelonephritis 2

Treatment Algorithm

For Cystitis (Lower UTI)

Empiric oral antibiotics should be initiated immediately after obtaining urine culture 5, 4

First-line options:

• Nitrofurantoin (avoid after 36 weeks gestation due to hemolytic anemia risk in newborn) 5, 4
• Fosfomycin trometamol 3g single dose 5, 4
• Third-generation cephalosporins (cefixime preferred for compliance and safety) 5

Duration: 4-7 days depending on agent selected 1

Avoid: Fluoroquinolones (teratogenic), trimethoprim in first trimester (neural tube defects), and empiric amoxicillin/co-amoxiclav due to high resistance rates 3, 4

For Pyelonephritis (Upper UTI)

Hospitalization with intravenous antibiotics is recommended for initial management 2, 5

Parenteral first-line options:

• Ceftriaxone 1-2g IV once daily 6, 2
• Amoxicillin combined with aminoglycoside 4
• Third-generation cephalosporins 4

Transition to oral therapy when afebrile for 24-48 hours based on culture sensitivities 6, 2

Total duration: 7-14 days 6, 2

Expected response: 95% of patients become afebrile within 48 hours, nearly 100% within 72 hours 6, 2

Imaging Decisions

Initial imaging is NOT indicated for uncomplicated pyelonephritis in pregnancy 6, 2

Obtain renal ultrasound if:

• Fever persists beyond 72 hours of appropriate antibiotics 6, 2
• Clinical deterioration occurs 6, 2
• History of urolithiasis or known anatomic abnormalities 6
• Diabetes mellitus or immunosuppression 2

Ultrasound is preferred over CT to avoid fetal radiation exposure; evaluates for obstruction, abscess, or stones 6, 2

Asymptomatic Bacteriuria Screening

All pregnant women should be screened for asymptomatic bacteriuria with urine culture at one of the initial prenatal visits 1

Treatment is strongly recommended when ASB is detected because:

• Reduces pyelonephritis risk from 20-35% to 1-4% 1
• May reduce preterm birth risk from 53 per 1000 to 14 per 1000 1
• Probably lowers very low birth weight risk from 137 per 1000 to 88 per 1000 1

Treatment duration for ASB: 4-7 days of antimicrobial therapy 1

Critical Pitfalls to Avoid

• Do not delay antibiotic treatment while waiting for culture results in symptomatic patients 2, 5
• Do not use empiric amoxicillin or co-amoxiclav due to high resistance rates demonstrated in pregnancy studies 3
• Do not rely on urinalysis alone for diagnosis—the positive predictive value is too low in pregnancy 1, 3
• Do not perform routine imaging in uncomplicated cases responding to therapy within 48-72 hours 6, 2
• Do not withhold treatment for asymptomatic bacteriuria despite recent Dutch data suggesting selective non-treatment; the IDSA maintains strong recommendation for universal screening and treatment pending further evidence 1
• Do not use fluoroquinolones or trimethoprim in first trimester due to teratogenic risks 4

Monitoring and Follow-up

• Clinical improvement should be evident within 48 hours of appropriate therapy 6, 2
• If fever persists beyond 72 hours, obtain imaging to rule out complications (abscess, obstruction, emphysematous pyelonephritis) 6, 2
• Adjust antibiotics based on culture and susceptibility results once available 1, 2
• Consider repeat urine culture after treatment completion to document clearance, though optimal frequency of repeat screening during pregnancy remains undefined 1