Nitrofurantoin in Third Trimester: Safety Profile
Yes, nitrofurantoin can be safely used during the third trimester of pregnancy and is recommended as a first-line agent for treating urinary tract infections during this period. 1, 2, 3
Primary Recommendation
The American College of Obstetricians and Gynecologists (ACOG) explicitly 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. 1, 2, 3
Supporting Safety Evidence
Animal Studies
- Nitrofurantoin macrocrystals administered 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. 4
- No teratogenic effects, reproductive capability impairment, or neonatal complications were observed across multiple reproductive toxicity studies. 4
Human Clinical Data
- A retrospective analysis of 91 pregnancies in 81 women treated with nitrofurantoin during pregnancy found no drug-related abnormal events. 5
- The incidence of fetal death, neonatal death, malformations, prematurity, low birth weight, low Apgar scores, and jaundice was not significantly different from the general U.S. population. 5
Important Clinical Caveat
Nitrofurantoin is contraindicated when creatinine clearance is <60 mL/min due to inadequate urinary drug concentrations and increased maternal toxicity risk. 6 This is particularly relevant in the third trimester when physiologic changes may affect renal function.
Dosing Regimen
- Standard dosing: 100 mg orally twice daily for 5-7 days for uncomplicated lower urinary tract infections. 7
- Alternative regimen: 50-100 mg four times daily for 5 days. 6
Key Principle
Untreated urinary tract infections during pregnancy pose serious risks to both mother and fetus that outweigh the minimal theoretical risks of nitrofurantoin therapy. 1, 2, 3 Pregnant women should not be denied appropriate antibiotic treatment when clinically indicated. 1, 2, 3