What is the appropriate treatment for an uncomplicated urinary tract infection in a pregnant adult?

Treatment of Urinary Tract Infection in Pregnant Adults

For uncomplicated UTI in pregnancy, prescribe nitrofurantoin 100 mg orally twice daily for 7 days as first-line therapy, or fosfomycin 3 g as a single oral dose as an equally acceptable alternative. 1

First-Line Antibiotic Options

Nitrofurantoin (Preferred)

• Nitrofurantoin 50–100 mg orally four times daily for 7 days is the recommended first-line agent for symptomatic UTI throughout pregnancy, including the first trimester. 2, 1
• This agent achieves high bactericidal urinary concentrations against E. coli (the causative organism in 75–95% of cases) with minimal resistance and excellent safety data. 1, 3
• A retrospective analysis of 91 pregnancies treated with nitrofurantoin macrocrystals reported no fetal toxicity or drug-related adverse events. 1
• Critical contraindication: Do not use nitrofurantoin for suspected pyelonephritis or upper urinary tract infections, as therapeutic blood concentrations are not achieved. 1

Fosfomycin (Equally Acceptable Alternative)

• Fosfomycin trometamol 3 g as a single oral dose provides therapeutic urinary concentrations for 24–48 hours and is explicitly recommended for both asymptomatic bacteriuria and symptomatic UTI in pregnancy. 2, 1, 4
• The single-dose regimen improves adherence and has minimal impact on intestinal flora. 4
• Fosfomycin is safe throughout pregnancy and offers convenience without compromising efficacy. 1, 4

Cephalosporins (Alternative When First-Line Agents Unsuitable)

• Cephalexin 500 mg orally four times daily for 7–14 days is recommended when nitrofurantoin or fosfomycin cannot be used. 1
• Other options include cefpodoxime or cefuroxime for the same duration. 1
• Cephalosporins achieve adequate blood and urinary concentrations with excellent pregnancy safety profiles. 1

Antibiotics to Avoid in Pregnancy

Trimethoprim-Sulfamethoxazole

• Contraindicated in the first trimester due to potential teratogenic effects (neural tube defects). 2, 1
• Contraindicated in the third trimester due to risk of neonatal hyperbilirubinemia and kernicterus. 2, 1

Fluoroquinolones

• Avoid throughout pregnancy due to potential adverse effects on fetal cartilage development and arthropathy demonstrated in juvenile animal studies. 1, 3
• Multiple guidelines explicitly recommend against fluoroquinolone use in pregnancy. 1

Diagnostic Approach

When to Obtain Urine Culture

• Always obtain urine culture before initiating treatment in pregnant women with suspected UTI to guide antibiotic selection. 1
• Screening for pyuria alone has only 50% sensitivity for identifying bacteriuria in pregnant women; urine culture is the gold standard. 1
• Optimal screening timing: 12–16 weeks gestation with a single urine culture for asymptomatic bacteriuria. 1

Dipstick Testing Limitations

• Urine dipstick is unreliable in pregnancy with poor positive and negative predictive value. 1, 3
• Negative dipstick does not rule out UTI in symptomatic pregnant women; empiric treatment should be initiated while awaiting culture results. 1

Treatment Duration and Follow-Up

Standard Course

• 7–14 days is the recommended treatment duration to ensure complete eradication, though the optimal duration remains uncertain. 1
• For asymptomatic bacteriuria, 4–7 days may be acceptable depending on the antimicrobial chosen. 1

Mandatory Follow-Up

• Obtain follow-up urine culture 1–2 weeks after completing treatment to confirm cure. 1
• If symptoms persist or recur within 2 weeks, obtain repeat culture with susceptibility testing and assume the organism is resistant to the original agent; retreat with a 7-day course of an alternative antibiotic. 1

Special Clinical Situations

Asymptomatic Bacteriuria

• Pregnancy is the one clinical scenario where asymptomatic bacteriuria must always be treated. 2, 1
• Screen for and treat asymptomatic bacteriuria in pregnant women with standard short-course treatment or single-dose fosfomycin. 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

Group B Streptococcus (GBS) Bacteriuria

• The presence of GBS bacteriuria in any concentration during pregnancy is a marker for heavy genital tract colonization and requires treatment at the time of diagnosis. 1
• Women with GBS bacteriuria also require intrapartum GBS prophylaxis during labor. 1

Pyelonephritis in Pregnancy

• For hospitalized pregnant women with pyelonephritis, initiate parenteral therapy with ceftriaxone 1–2 g daily or cefepime 1–2 g twice daily. 1
• Transition to oral cephalosporin therapy after clinical improvement for completion of a 7–14 day course. 1
• Agents that do not achieve therapeutic blood concentrations (nitrofurantoin, fosfomycin) should not be used for pyelonephritis. 1

Recurrent UTIs During Pregnancy

• For recurrent UTIs, consider prophylactic antibiotics (cephalexin) for the remainder of pregnancy. 1
• Postcoital prophylaxis with cephalexin 250 mg or nitrofurantoin macrocrystals 50 mg as a single oral dose is highly effective. 5

Critical Pitfalls to Avoid

• Do not delay treatment in pregnant women with symptomatic UTI, as this increases the risk of pyelonephritis and adverse pregnancy outcomes. 1
• Do not use nitrofurantoin near term (after 38 weeks) due to theoretical risk of neonatal hemolytic anemia, though evidence is limited. 1
• Do not treat asymptomatic bacteriuria repeatedly after the initial screen-and-treat approach, as this fosters antimicrobial resistance. 1
• Do not rely on dipstick testing alone to rule out UTI in symptomatic pregnant women. 1, 3

Treatment Algorithm

Step 1: Obtain urine culture immediately in any pregnant woman with urinary symptoms or positive screening. 1

Step 2: Initiate empiric therapy without waiting for culture results:

• First choice: Nitrofurantoin 100 mg orally twice daily for 7 days 1
• Equally acceptable: Fosfomycin 3 g single oral dose 1
• Alternative: Cephalexin 500 mg orally four times daily for 7–14 days 1

Step 3: Adjust therapy based on culture and susceptibility results if needed. 1

Step 4: Obtain follow-up urine culture 1–2 weeks after treatment completion to confirm cure. 1

Step 5: If symptoms persist or recur, obtain repeat culture and switch to a different antibiotic class for 7 days. 1