Management of Urinary Tract Infections in Pregnancy
Screening and Diagnosis
All pregnant women should be screened for asymptomatic bacteriuria with a urine culture at 12-16 weeks gestation, as untreated bacteriuria increases pyelonephritis risk 20-30 fold (from 1-4% with treatment to 20-35% without treatment). 1, 2
- Pregnancy is the only clinical scenario where asymptomatic bacteriuria must always be treated due to significant risks of pyelonephritis, preterm birth, and low birth weight infants 1, 2
- Screening for pyuria alone has only 50% sensitivity for identifying bacteriuria and is inadequate 1, 2
- Always obtain a urine culture before initiating treatment to guide antibiotic selection 1, 2
- Women with GBS bacteriuria in any concentration require treatment at diagnosis plus intrapartum GBS prophylaxis during labor 1, 2
First-Line Antibiotic Treatment
First Trimester
Nitrofurantoin (50-100 mg four times daily for 5-7 days) is the first-line antibiotic for UTI in the first trimester, with fosfomycin trometamol (3g single dose) as an acceptable alternative. 2
- Avoid trimethoprim and trimethoprim-sulfamethoxazole in the first trimester due to potential teratogenic effects 2
- Cephalosporins (cephalexin 500 mg four times daily) are appropriate alternatives with excellent safety profiles 2
- Fluoroquinolones should be avoided throughout pregnancy due to potential adverse effects on fetal cartilage development 2
Second and Third Trimesters
Cephalosporins such as cephalexin, cefpodoxime, or cefuroxime are appropriate first-line options for the second and third trimesters. 2
- Nitrofurantoin should be avoided near term (after 36 weeks) due to theoretical risk of hemolytic anemia in the newborn 2
- Amoxicillin-clavulanate (20-40 mg/kg per day in 3 doses) is appropriate if the pathogen is susceptible 2
- Fosfomycin (single 3g dose) can be considered for uncomplicated lower UTIs, though clinical data is more limited 2
Treatment Duration
The standard treatment course is 7-14 days to ensure complete eradication of infection. 2
- For asymptomatic bacteriuria, 4-7 days of antimicrobial treatment is acceptable, with the shortest effective course preferred 1, 2
- Insufficient evidence exists to support single-dose, 3-day, or 4-day regimens over 7-day courses 2
Pyelonephritis Management
For suspected pyelonephritis or severe infections, initial parenteral therapy is required, with transition to oral therapy after clinical improvement. 2
- Agents that do not achieve therapeutic blood concentrations (such as nitrofurantoin and fosfomycin) should not be used for pyelonephritis 2
- Cephalosporins achieve adequate blood and urinary concentrations and are preferred 2
Follow-Up and Monitoring
Obtain a follow-up urine culture 1-2 weeks after completing treatment to confirm cure. 2
- Do not perform surveillance urine testing or repeatedly treat asymptomatic bacteriuria after the initial screen-and-treat approach, as this fosters antimicrobial resistance 2
- For recurrent UTIs, consider prophylactic antibiotics (cephalexin or nitrofurantoin 50 mg) for the remainder of pregnancy 2, 3
Critical Pitfalls to Avoid
- 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 use fluoroquinolones at any point during pregnancy despite their efficacy in non-pregnant women 2
- Do not delay treatment in pregnant women with symptomatic UTI, as this increases risk of pyelonephritis and adverse pregnancy outcomes 2
- Antibiotic choice must consider local resistance patterns and patient-specific factors such as allergies 2
Prophylaxis for Recurrent UTI
For women with a history of recurrent UTIs, postcoital prophylaxis with a single oral dose of either cephalexin (250 mg) or nitrofurantoin macrocrystals (50 mg) is highly effective. 3