The treatment of symptomatic and asymptomatic bacteriuria is impoant to prevent complications in pregnancy. Empiric treatment for common organisms such as Escherichia coli and Proteus should be administered while maintaining safety. Penicillins and cephalosporins, such as cephalexin (D), are safe for use during pregnancy. Nitrofurantoins are also effective. Trimethoprim (A) is a folic acid antagonist and therefore should be avoided in pregnancy, especially in the first trimester of pregnancy as in this patient. Fluoroquinolones (B) and tetracyclines (C) are also known teogens and must also be avoided in pregnancy.