What is the recommended treatment for a pregnant female with a urinary tract infection (UTI)?

Treatment of UTI in Pregnancy

Nitrofurantoin (50-100 mg four times daily for 5-7 days) or fosfomycin (3g single dose) are the first-line treatments for UTI in pregnancy, with cephalosporins (such as cephalexin 500 mg four times daily for 7-14 days) as appropriate alternatives. 1, 2

Antibiotic Selection by Trimester

First Trimester

• Nitrofurantoin is the preferred first-line agent for uncomplicated UTI in the first trimester 1
• Fosfomycin trometamol (3g single dose) is an acceptable alternative with the advantage of single-dose administration 1, 2
• Cephalosporins (cephalexin, cefpodoxime, cefuroxime) are appropriate alternatives if nitrofurantoin or fosfomycin cannot be used 1
• Avoid trimethoprim-sulfamethoxazole in the first trimester due to potential teratogenic effects 1, 2
• Avoid fluoroquinolones throughout all trimesters due to potential adverse effects on fetal cartilage development 1

Second Trimester

• Same antibiotic options as first trimester apply 1, 2
• Nitrofurantoin, fosfomycin, and cephalosporins remain safe and effective 1

Third Trimester

• Cephalexin (500 mg four times daily for 7-14 days) becomes the preferred first-line agent in the third trimester 1
• Avoid nitrofurantoin near term due to risk of hemolytic anemia in the newborn 2
• Fosfomycin (3g single dose) can be considered for uncomplicated lower UTIs, though clinical data is more limited than for cephalosporins 1
• Amoxicillin-clavulanate (20-40 mg/kg per day in 3 doses) is appropriate if the pathogen is susceptible 1
• Avoid trimethoprim-sulfamethoxazole in the third trimester due to risk of neonatal hyperbilirubinemia and kernicterus 1, 2

Treatment Duration

• Standard treatment course is 7-14 days for symptomatic UTI in pregnancy 1
• 5-7 days is acceptable depending on the antimicrobial chosen 1, 2
• Shorter courses (1-3 days) are generally not recommended for pregnant women 2
• Single-dose fosfomycin is the exception to multi-day regimens and is equally effective for uncomplicated cystitis 2

Diagnostic Requirements

• Always obtain urine culture before initiating treatment to guide antibiotic selection and confirm diagnosis 1, 2
• Optimal screening timing is at 12-16 weeks gestation 1
• Screening for pyuria alone has only 50% sensitivity for identifying bacteriuria and is inadequate 1
• Obtain follow-up urine culture 1-2 weeks after completing treatment to confirm cure 1

Special Clinical Scenarios

Asymptomatic Bacteriuria (ASB)

• Pregnancy is the one clinical scenario where ASB must always be treated due to significant risk for progression to pyelonephritis and adverse pregnancy outcomes 1, 2
• 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
• Use the same antibiotic options and duration as for symptomatic UTI 1, 2

Group B Streptococcus (GBS) Bacteriuria

• GBS bacteriuria in any concentration during pregnancy requires treatment at diagnosis AND intrapartum prophylaxis during labor 1
• GBS bacteriuria is a marker for heavy genital tract colonization 1

Suspected Pyelonephritis

• Do not use nitrofurantoin for suspected pyelonephritis as it does not achieve therapeutic concentrations in the bloodstream 1
• Initial parenteral therapy may be required, with transition to oral therapy after clinical improvement 1
• Cephalosporins achieve adequate blood and urinary concentrations and are appropriate for pyelonephritis 1

Recurrent UTIs

• Consider prophylactic antibiotics (cephalexin) for the remainder of pregnancy in cases of recurrent UTIs 1
• Daily low-dose antibiotics can be used in select cases with frequent recurrences 2
• Do not perform surveillance urine testing or treat ASB repeatedly after the initial screen-and-treat approach, as this fosters antimicrobial resistance 1

Penicillin Allergy Considerations

• Only 10% of penicillin-allergic patients have reactions to cephalosporins 1
• Assess whether the patient is at high risk for anaphylaxis; if not, cephalosporins are safe 1
• If true severe penicillin allergy exists, nitrofurantoin or fosfomycin are appropriate alternatives 1, 2

Critical Pitfalls to Avoid

• Never delay treatment in pregnant women with symptomatic UTI, as this increases the risk of pyelonephritis and adverse pregnancy outcomes 1
• Do not use antibiotics that fail to achieve adequate urinary concentrations (such as certain macrolides) 2
• Do not classify all pregnant women with UTIs as requiring broad-spectrum antibiotics unless they have structural/functional urinary tract abnormalities or immunosuppression 1
• Antibiotic choice must consider local resistance patterns and patient-specific factors such as allergies 1, 2