Macrobid (Nitrofurantoin) for UTI in Pregnancy
Nitrofurantoin is an appropriate and effective treatment for UTIs during pregnancy, particularly as a first-line agent for uncomplicated lower urinary tract infections and asymptomatic bacteriuria, but should be avoided near term (after 38 weeks gestation) due to theoretical risk of neonatal hemolytic anemia. 1
Treatment Recommendations by Trimester
First and Second Trimester
- Nitrofurantoin is recommended as first-line therapy for uncomplicated UTIs and asymptomatic bacteriuria during the first and second trimesters 1
- Fosfomycin (3g single dose) serves as an acceptable alternative 1
- Treatment duration should be 7-14 days to ensure complete eradication 1
- Always obtain a urine culture before initiating treatment to guide therapy 1
Third Trimester (Before 38 Weeks)
- Nitrofurantoin can be used safely in early third trimester 1
- After 38 weeks gestation, avoid nitrofurantoin due to theoretical risk of hemolytic anemia in neonates with G6PD deficiency 1
Alternative Agents When Nitrofurantoin is Contraindicated
- Cephalexin 500 mg four times daily for 7-14 days is the preferred alternative 1
- Cephalosporins (cephalexin, cefpodoxime, cefuroxime) achieve excellent blood and urinary concentrations with proven safety profiles 1
- Amoxicillin-clavulanate is appropriate if the pathogen is susceptible 1
Critical Clinical Context
Why Treatment Matters
- Untreated bacteriuria increases pyelonephritis risk 20-30 fold (from 20-35% to 1-4% with treatment) 2
- Treatment reduces premature delivery and low birth weight infants 2
- Implementation of screening programs decreased pyelonephritis rates from 1.8-2.1% to 0.5-0.6% 2
Safety Profile of Nitrofurantoin
- Over 35 years of clinical use with continuing safety record 3
- Animal studies at 2-6 times human therapeutic doses showed no maternal, fetal, or neonatal adverse effects 4
- Retrospective analysis of 91 pregnancies showed no drug-related abnormal events, with outcomes similar to general US population 5
- Highly effective for prophylaxis: reduced 130 UTIs pre-pregnancy to only 1 UTI during pregnancy in women with recurrent infections 6
Agents to Avoid
First Trimester Contraindications
- Avoid trimethoprim and trimethoprim-sulfamethoxazole due to potential teratogenic effects including anencephaly, heart defects, and orofacial clefts 1, 7
- Avoid fluoroquinolones throughout pregnancy due to potential adverse effects 1
Pyelonephritis Exception
- Do not use nitrofurantoin for suspected pyelonephritis as it does not achieve therapeutic bloodstream concentrations 1
- Use cephalosporins or other agents that achieve adequate blood levels for systemic infections 1
Follow-Up Protocol
- Obtain follow-up urine culture 1-2 weeks after completing treatment to confirm cure 1
- For recurrent UTIs, consider prophylactic cephalexin for remainder of pregnancy 1
- Women with Group B Streptococcus bacteriuria require treatment at diagnosis plus intrapartum prophylaxis during labor 1
Common Pitfall
Despite ACOG 2011 recommendations suggesting caution with nitrofurantoin in first trimester, the extensive safety data and guideline support demonstrate it remains a first-line option. The key restriction is avoiding use after 38 weeks gestation, not during early pregnancy. 1, 7