The risks and benefits of antimicrobial therapy in pregnancy.

Antimicrobial agents, especially antibiotics, are prescribed in pregnancy for various specific indications related to pregnancy per se (e.g. chorioamnionitis), for infections otherwise unrelated to but complicating pregnancy (e.g. pneumonia, bacterial endocarditis) and prophylactically for conditions which if untreated would have an adverse outcome for the pregnancy (e.g. asymptomatic bacteriuria). The selection of an agent will depend on the likely pathogen, stage of pregnancy, special pharmacokinetic factors related to the stage of pregnancy, safety of the drug and cost. Some classes of antibiotics can be taken throughout the 3 trimesters (e.g. beta-lactams), while others are completely contraindicated (e.g. tetracyclines) and others are to be avoided in certain trimesters (e.g. sulphas are contraindicated in the third trimester). The choice of an appropriate antimicrobial agent must be weighed against the potential adverse outcome of a particular infection, the drug safety and spectrum of activity.