Q. A 32-year-old woman who is 14 weeks pregnant comes to your office for routine follow-up. She is taking appropriate folic acid supplementation. A screening test for gestational diabetes is negative. Urinalysis shows a white blood cell count of 3 per high-power field and no red blood cells, protein, or glucose. Urine culture grows 105 colony-forming units/mL of Escherichia coli, which is sensitive to one antibiotic. The patient is asymptomatic. What is the most appropriate next step?

A. A second urinalysis and culture in the third trimester

B. Ciprofloxacin (Cipro) for 3 days

C.  Double-strength trimethoprim/sulfamethoxazole (TMX/SMX; Bactrim DS) for 3 days, followed by prophylactic TMP/SMX until delivery

D. Nitrofurantoin (Macrobid, Macrodantin) for 7 days, followed by frequent screening for recurrence