What is the recommended treatment for a urinary tract infection (UTI) in pregnant women?

Treatment of UTI During Pregnancy

Pregnant women with symptomatic UTI should be treated with nitrofurantoin (100 mg four times daily for 5-7 days) or cephalexin (500 mg four times daily for 7-14 days) as first-line therapy, with treatment duration of 4-7 days minimum to prevent pyelonephritis and adverse pregnancy outcomes. 1, 2

Diagnostic Approach

• Obtain urine culture before initiating treatment in all pregnant women with suspected UTI to guide antibiotic selection and confirm diagnosis 2, 3
• Screen for asymptomatic bacteriuria at least twice during pregnancy (early pregnancy and third trimester), as untreated bacteriuria significantly increases risk of pyelonephritis and preterm labor 1, 3
• Treat all cases of asymptomatic bacteriuria in pregnancy (≥10⁵ CFU/mL), unlike in non-pregnant populations where treatment is not recommended 1, 3

First-Line Antibiotic Options

Nitrofurantoin

• Dosing: 100 mg orally four times daily for 5-7 days 1, 3
• Preferred first-line agent with excellent safety profile and low resistance rates 2, 3
• Critical caveat: Contraindicated after 37 weeks of pregnancy due to risk of neonatal hemolytic anemia 3
• Do not use for pyelonephritis as it does not achieve therapeutic blood concentrations 2

Cephalosporins

• Cephalexin 500 mg orally four times daily for 7-14 days is the preferred cephalosporin 2
• Cefpodoxime and cefuroxime are acceptable alternatives 2
• Achieve adequate blood and urinary concentrations with excellent pregnancy safety profiles 2
• Appropriate for all trimesters including third trimester and for suspected pyelonephritis 2

Fosfomycin

• Single 3-gram dose for uncomplicated lower UTI 2, 3
• Acceptable alternative, particularly for first trimester 2
• Limited clinical data for third trimester use and outcomes such as pyelonephritis prevention 1

Second-Line Options

• Amoxicillin-clavulanate: 20-40 mg/kg per day in 3 divided doses for 7 days if pathogen is susceptible 2, 3
• Amoxicillin alone has higher failure rates due to E. coli resistance and should be avoided 4

Antibiotics to AVOID

• Trimethoprim-sulfamethoxazole: Contraindicated in first trimester due to teratogenic effects (neural tube defects, cardiac defects, orofacial clefts) 2, 5
• Fluoroquinolones (ciprofloxacin): Avoid throughout entire pregnancy due to potential adverse fetal effects 2, 5
• Sulfonamides: Should not be used in first trimester; associated with birth defects 5

Treatment Duration

• Minimum 4-7 days of therapy for symptomatic UTI and asymptomatic bacteriuria 1
• 7-14 days total course recommended to ensure complete eradication, particularly with cephalosporins 2
• Single-dose therapy is less effective than 7-day courses for preventing low birth weight (RR 1.65,95% CI 1.06-2.57) 1

Management of Pyelonephritis

• Initial parenteral therapy required for severe infections or pyelonephritis 2
• Use second or third-generation cephalosporins administered intravenously during hospitalization 4
• Transition to oral therapy after clinical improvement 2
• Agents like nitrofurantoin that don't achieve therapeutic blood concentrations must not be used 2

Special Considerations

Group B Streptococcus (GBS)

• GBS bacteriuria at any concentration during pregnancy requires treatment at time of diagnosis 2
• Also requires intrapartum GBS prophylaxis during labor 2

Follow-up

• Repeat urine culture 1-2 weeks after completing treatment to confirm cure 2
• For recurrent UTIs, consider prophylactic antibiotics (cephalexin or nitrofurantoin before 37 weeks) for remainder of pregnancy 2, 3

Common Pitfalls to Avoid

• Do not delay treatment while awaiting culture results if symptomatic, as this increases risk of pyelonephritis and adverse pregnancy outcomes 2
• Do not treat based on dipstick or urinalysis alone without culture in pregnant women 2
• Do not use nitrofurantoin after 37 weeks gestation 3
• Do not prescribe single-dose therapy as it has inferior outcomes compared to 7-day courses 1
• Remember that ampicillin has high E. coli resistance and should not be used empirically 4