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

Treatment of UTI in Pregnancy

Pregnant women with symptomatic UTI should be treated with nitrofurantoin (50-100 mg four times daily for 5-7 days) or fosfomycin trometamol (3g single dose) as first-line therapy, with cephalosporins (such as cephalexin 500 mg four times daily for 7-14 days) as appropriate alternatives, and a urine culture must always be obtained before initiating treatment. 1, 2

Key Diagnostic Requirements

Always obtain a urine culture before treatment in pregnant women with suspected UTI, as screening for pyuria alone has only 50% sensitivity for identifying bacteriuria 2, 3. The optimal screening timing is at 12-16 weeks gestation 2.

First-Line Antibiotic Options by Trimester

First Trimester

• Nitrofurantoin is the preferred first-line agent (50-100 mg four times daily for 5-7 days) 1, 2
• Fosfomycin trometamol (3g single dose) is an acceptable alternative 1, 2
• Cephalexin 500 mg four times daily for 7-14 days is appropriate if the above are contraindicated 2
• Avoid trimethoprim and trimethoprim-sulfamethoxazole in the first trimester due to potential teratogenic effects 2

Second and Third Trimesters

• Cephalosporins (cephalexin, cefpodoxime, or cefuroxime) are preferred options, particularly in the third trimester where nitrofurantoin should be avoided near delivery 2
• Fosfomycin (3g single dose) can be considered for uncomplicated lower UTIs 2
• Amoxicillin-clavulanate (20-40 mg/kg per day in 3 doses) if the pathogen is susceptible 2

Antibiotics to Avoid Throughout Pregnancy

• Fluoroquinolones (including ciprofloxacin) should be avoided throughout pregnancy due to potential adverse effects on fetal cartilage development 2, 4
• Trimethoprim-sulfamethoxazole should not be used in the first trimester and is contraindicated in the last trimester 1, 2

Treatment Duration

The total course of therapy should be 7-14 days to ensure complete eradication of the infection 2. While the optimal duration remains uncertain, Cochrane reviews found insufficient evidence to support shorter regimens (single-dose, 3-day, or 4-day courses) over 7-day courses 2, 5.

Critical Clinical Context: Why Treatment is Essential

• Untreated bacteriuria increases pyelonephritis risk 20-30 fold (from 1-4% with treatment to 20-35% without treatment) 2, 3
• Treatment reduces premature delivery and low birth weight infants 2, 6
• Implementation of screening programs decreased pyelonephritis rates from 1.8-2.1% to 0.5-0.6% 2

Asymptomatic Bacteriuria in Pregnancy

Screen for and treat asymptomatic bacteriuria in pregnant women with standard short-course treatment or single-dose fosfomycin trometamol 1. Pregnancy is the one clinical scenario where asymptomatic bacteriuria must always be treated, as it carries significant risk for progression to pyelonephritis and adverse pregnancy outcomes 2, 6.

Special Considerations

Group B Streptococcus (GBS)

GBS bacteriuria in any concentration during pregnancy is a marker for heavy genital tract colonization and requires treatment at the time of diagnosis as well as intrapartum GBS prophylaxis during labor 2.

Pyelonephritis

• Agents that do not achieve therapeutic concentrations in the bloodstream (such as nitrofurantoin) should not be used for suspected pyelonephritis 2
• Initial parenteral therapy may be required for severe infections or pyelonephritis, with transition to oral therapy after clinical improvement 2
• Preferred antimicrobials include amoxicillin combined with an aminoglycoside, third-generation cephalosporins, or carbapenems 3

Penicillin Allergy

Only 10% of penicillin-allergic patients have reactions to cephalosporins 2. Assess whether the patient is at high risk for anaphylaxis; if not, cephalosporins are safe 2.

Follow-Up

Follow-up urine culture 1-2 weeks after completing treatment is recommended to confirm cure 2. For recurrent UTIs, consider prophylactic antibiotics (cephalexin) for the remainder of pregnancy 2.

Common Pitfalls to Avoid

• Do not treat asymptomatic bacteriuria repeatedly after the initial screen-and-treat approach, as this fosters antimicrobial resistance 2
• Do not classify pregnant women with UTIs as "complicated" unless they have structural/functional urinary tract abnormalities or immunosuppression, as this leads to unnecessary broad-spectrum antibiotic use 2
• Do not delay treatment in pregnant women with symptomatic UTI, as this increases the risk of pyelonephritis and adverse pregnancy outcomes 2