Nitrofurantoin Safety in Second Trimester for UTI
Nitrofurantoin is safe and appropriate for treating urinary tract infections during the second trimester of pregnancy. 1
First-Line Treatment Recommendation
- Nitrofurantoin (50-100 mg four times daily for 7 days) is recommended as a first-line agent for UTI treatment throughout the second trimester. 1
- The European Association of Urology guidelines explicitly endorse nitrofurantoin for symptomatic UTI in pregnant women, with fosfomycin trometamol (3g single dose) as an acceptable alternative. 1
- Treatment duration should be 7-14 days to ensure complete eradication, though 7 days is standard for symptomatic UTI. 1
Safety Evidence Supporting Second Trimester Use
- The American College of Obstetricians and Gynecologists (ACOG) states that nitrofurantoin may continue to be used as a first-line agent during the second and third trimesters for treatment and prevention of urinary tract infections. 2
- Animal studies at doses 2-6 times the human therapeutic dose showed no adverse effects on maternal health, fetal development, or neonatal survival in rats and rabbits. 3
- A retrospective analysis of 91 pregnancies treated with nitrofurantoin macrocrystals found no drug-related abnormal events, with outcomes comparable to the general U.S. population. 4
- Nitrofurantoin has maintained a continuing safety record over 35+ years of clinical use in obstetrics. 5
Critical Trimester-Specific Considerations
- First trimester: Nitrofurantoin remains appropriate when no suitable alternatives exist, though some guidelines express more caution. 1, 2
- Second trimester: Full endorsement as first-line therapy with no restrictions. 1, 2
- Third trimester: Should be avoided near term due to theoretical risk of hemolytic anemia in the newborn. 1
Important Clinical Context
- Untreated UTI in pregnancy increases pyelonephritis risk 20-30 fold (from 1-4% with treatment to 20-35% without treatment). 1
- Treatment reduces premature delivery and low birth weight infants. 1
- Always obtain urine culture before initiating treatment to guide therapy, though empiric treatment should not be delayed. 1
- Follow-up urine culture 1-2 weeks after completing treatment is recommended to confirm cure. 1
When NOT to Use Nitrofurantoin
- Do not use nitrofurantoin for suspected pyelonephritis, as it does not achieve therapeutic concentrations in the bloodstream. 1
- For pyelonephritis requiring hospitalization, use parenteral ceftriaxone (1-2g daily) or cefepime (1-2g twice daily) initially. 1
Common Pitfall to Avoid
- Do not withhold appropriate antibiotic treatment due to pregnancy concerns—untreated infections pose far greater maternal and fetal risks than appropriate antibiotic use. 2