A pregnant woman at 13 weeks with a urinary tract infection is treated. What is an appropriate first-line antibiotic regimen?

• A. Amoxicillin 500 mg QID for 7 days
• B. Cefalexin 500 mg QID for 7 days
• C. Ceftriaxone 1 g IV daily for 3 days
• D. Nitrofurantoin 50 mg tablets QDS for 7 days

Answer: (D)

Treat UTIs in pregnancy with an antibiotic that is both effective against common urine pathogens and safe for the fetus. Nitrofurantoin fits this need because it concentrates in urine and is effective for lower urinary tract infections caused by organisms like E. coli. At 13 weeks, a regimen of 50 mg taken four times daily for seven days provides reliable urinary exposure and an appropriate treatment duration, making it a preferred first-line option for a stable early-pregnancy patient with cystitis. It should not be used if there are signs of pyelonephritis or systemic infection (which would require IV therapy), if renal function is impaired, or near term due to rare risks of neonatal hemolysis in G6PD deficiency. Other options are either less ideal in pregnancy due to safety or resistance concerns, or reserved for more serious infection requiring parenteral therapy.