What is the most appropriate treatment for a pregnant woman diagnosed with a urinary tract infection caused by Escherichia coli?

For a pregnant woman diagnosed with a urinary tract infection (UTI) caused by Escherichia coli, the most appropriate treatment is amoxicillin. This antibiotic is categorized as a pregnancy category B drug, indicating that it is generally considered safe for use during pregnancy. Amoxicillin effectively targets most strains of E. coli responsible for UTIs and has a well-established safety profile in pregnant patients, making it a suitable choice for treating this infection while minimizing risks to both the mother and the fetus.

Other options, such as metronidazole and trimethoprim-sulfamethoxazole, are not ideal choices for this scenario. Metronidazole, although effective against certain organisms, is typically used for anaerobic infections and is not the first-line treatment for UTIs caused by E. coli. Trimethoprim-sulfamethoxazole is often contraindicated in the first trimester and near delivery due to potential risks to fetal development and possible hyperbilirubinemia in newborns. Meanwhile, the option stating that no antibiotic therapy is needed does not apply here, as untreated UTIs during pregnancy can lead to complications, including pyelonephritis and preterm labor.

Thus, based on the efficacy and safety profile for