Can Macrobid (nitrofurantoin) be given during pregnancy?

Macrobid Use During Pregnancy

Macrobid (nitrofurantoin) can be safely used during the second and third trimesters of pregnancy for urinary tract infections, but should be avoided in the first trimester unless no suitable alternatives exist, and must be avoided near term delivery. 1

Trimester-Specific Recommendations

Second and Third Trimesters (Weeks 14-36)

• Nitrofurantoin may be used as a first-line agent for treatment and prevention of urinary tract infections caused by susceptible organisms 1
• The drug has demonstrated safety in multiple studies with no significant increase in fetal abnormalities compared to the general population 2
• Effective for prophylaxis of recurrent UTIs: in one study, only 1 UTI occurred during 39 pregnancies using postcoital prophylaxis (50 mg nitrofurantoin macrocrystals), compared to 130 UTIs before prophylaxis 3

First Trimester (Weeks 4-13)

• Use only when no other suitable alternative antibacterics are available 1
• The evidence is mixed regarding birth defects, making cautious prescribing appropriate 1
• Penicillins and cephalosporins are safer first-line choices during this period 4

Near Term (After Week 36) and at Delivery

• Nitrofurantoin must be avoided near delivery due to risk of neonatal hemolytic anemia in newborns with immature enzyme systems 4
• This contraindication is critical and non-negotiable 4

Preferred Alternatives by Trimester

First trimester safer options include:

• Penicillins (amoxicillin) - safest class, not teratogenic 4
• Cephalosporins (cefuroxime) - not teratogenic at usual therapeutic doses 4

Antibiotics to absolutely avoid in pregnancy:

• Tetracyclines (including doxycycline) - cause tooth discoloration and bone growth suppression 4
• Fluoroquinolones (ciprofloxacin) - potential fetal cartilage damage 4
• Trimethoprim-sulfamethoxazole in first trimester - associated with fetal abnormalities 4
• Aminoglycosides - eighth cranial nerve toxicity risk 4

Clinical Considerations

When prescribing nitrofurantoin during pregnancy:

• Use only for appropriate indications and shortest effective duration 1
• Standard therapeutic dose should not exceed 16 mg/day (though typical UTI dosing is 100 mg twice daily for macrocrystals) 5
• The macrocrystal formulation (Macrodantin/Macrobid) has been specifically studied in pregnancy with reassuring safety data 2, 3

Critical caveat: Untreated urinary tract infections during pregnancy pose serious risks including pyelonephritis, preterm labor, and low birth weight 2, 3. Therefore, pregnant women should not be denied appropriate antibiotic treatment when indicated 1. The risk-benefit calculation favors treatment of documented infections even in the first trimester if safer alternatives are unavailable 1.