Is Macrobid (nitrofurantoin) safe to use during pregnancy?

Macrobid (Nitrofurantoin) Safety During Pregnancy

Nitrofurantoin is safe and appropriate to use during the second and third trimesters of pregnancy as a first-line agent for urinary tract infections, but should be avoided near delivery due to risk of neonatal hemolytic anemia and hyperbilirubinemia. 1, 2

Trimester-Specific Guidance

Second and Third Trimesters (Safe Period)

• Nitrofurantoin may continue to be used as a first-line agent for treatment and prevention of urinary tract infections during the second and third trimesters. 1, 2
• The drug reaches high bactericidal concentrations in the urinary tract with minimal resistance development, making it highly effective for UTI prophylaxis during pregnancy. 3
• A retrospective analysis of 91 pregnancies treated with nitrofurantoin macrocrystals showed no significant difference in adverse fetal outcomes compared to the general U.S. population, with no drug-related abnormal events identified. 4

First Trimester (Use with Caution)

• Evidence regarding birth defects in the first trimester is mixed, but prescribing nitrofurantoin in the first trimester is still considered appropriate when no other suitable alternative antibiotics are available. 1, 2
• The European Respiratory Society classifies nitrofurantoin as "possibly safe" during the first trimester. 5
• Pregnant women should not be denied appropriate treatment for infections, as untreated infections commonly lead to serious maternal and fetal complications. 1, 2

At Term/Near Delivery (Contraindicated)

• Nitrofurantoin should be avoided at delivery due to risk of neonatal hyperbilirubinemia and hemolytic anemia. 5
• This risk is similar to that seen with sulfonamides and relates to the newborn's immature enzyme systems. 5

Clinical Algorithm for Use

When treating UTIs in pregnancy:

1. Weeks 14-37: Use nitrofurantoin as first-line therapy without hesitation 1, 2
2. First trimester (weeks 1-13): Use nitrofurantoin if no equally effective alternatives exist; the risk of untreated infection outweighs theoretical teratogenic concerns 1, 2
3. Week 38 onward: Switch to alternative antibiotic to avoid neonatal complications 5

Prophylactic Use

• Postcoital prophylaxis with nitrofurantoin macrocrystals 50 mg is highly effective for preventing recurrent UTIs during pregnancy. 3
• In one study, 130 UTIs occurred before prophylaxis versus only one UTI during pregnancy with prophylaxis—a highly significant reduction. 3

Key Clinical Pitfall

The most common error is unnecessarily avoiding nitrofurantoin throughout pregnancy due to outdated concerns. The critical period to avoid is only near delivery, not the entire pregnancy. 5, 1, 2 Withholding treatment increases the risk of pyelonephritis, preterm labor, and low birth weight—outcomes far more dangerous than the medication itself. 1, 2