Safe UTI Treatment During Pregnancy
Nitrofurantoin and cephalosporins (such as cephalexin) are the safest first-line antibiotics for treating UTIs during pregnancy, with treatment duration of 7-14 days recommended to prevent progression to pyelonephritis and adverse pregnancy outcomes. 1
First-Line Treatment Options by Trimester
First Trimester
- Nitrofurantoin is the preferred first-line agent for uncomplicated lower UTI in the first trimester 1
- Fosfomycin (single 3g dose) serves as an acceptable alternative 1
- Avoid trimethoprim-sulfamethoxazole and trimethoprim in the first trimester due to teratogenic effects 1
- Cephalosporins (cephalexin, cefpodoxime, cefuroxime) are appropriate alternatives with excellent safety profiles 1
Second and Third Trimesters
- Cephalexin 500 mg four times daily for 7-14 days is recommended as first-line therapy 1
- Nitrofurantoin remains safe but should be avoided near term (after 36 weeks) due to theoretical risk of neonatal hemolysis 1
- Amoxicillin-clavulanate (20-40 mg/kg per day in 3 doses) if pathogen is susceptible 1
- Fosfomycin can be considered for uncomplicated lower UTIs, though data is more limited 1
Critical Management Principles
Always Obtain Urine Culture First
- Obtain urine culture before initiating treatment to guide antibiotic selection 1
- Ideally performed at 12-16 weeks gestation for screening 1
- Follow-up culture 1-2 weeks after completing treatment to confirm cure 1
Treatment Duration
- 7-14 days of therapy is required to ensure complete eradication 1
- Shorter courses have insufficient evidence in pregnancy 1
When NOT to Use Nitrofurantoin
- Do not use nitrofurantoin for suspected pyelonephritis as it does not achieve therapeutic blood concentrations 1
- For pyelonephritis, use cephalosporins with initial parenteral therapy if severe, transitioning to oral after clinical improvement 1
Special Considerations
Penicillin Allergy
- Only 10% of penicillin-allergic patients react to cephalosporins 1
- Assess anaphylaxis risk; if low, cephalosporins remain safe 1
Group B Streptococcus (GBS) Bacteriuria
- Any concentration of GBS bacteriuria requires treatment at diagnosis plus intrapartum prophylaxis during labor 1
- This indicates heavy genital tract colonization 1
Recurrent UTIs During Pregnancy
- Consider prophylactic cephalexin for remainder of pregnancy 1
- Postcoital prophylaxis with cephalexin 250 mg or nitrofurantoin 50 mg has proven highly effective, reducing UTI incidence from 130 infections to only 1 during pregnancy 2
Why Treatment Cannot Be Delayed
Untreated bacteriuria increases pyelonephritis risk 20-30 fold (from 20-35% to 1-4% with treatment) 1. Treatment significantly reduces premature delivery and low birth weight 1. Screening programs decreased pyelonephritis rates from 1.8-2.1% to 0.5-0.6% 1.
Antibiotics to Avoid Throughout Pregnancy
- Fluoroquinolones should never be used due to potential adverse effects 1
- Trimethoprim/TMP-SMX in first trimester due to teratogenic risk 1
Evidence Quality Note
The safety profile of nitrofurantoin is supported by over 35 years of clinical use with continuing safety record and lack of resistance development 3. Retrospective analysis of 91 pregnancies showed no drug-related abnormal events or fetal toxicity 4. Fosfomycin has demonstrated equivalent efficacy and safety to nitrofurantoin in meta-analysis 5.