When choosing an antimicrobial agent for use in pregnancy, its pharmac
okinetics and toxicity in both the mother and fetus must be considered
. Because experimental evaluation of these factors cannot ethically be
determined in pregnancy, recommendations for use are based on studies
in animals as well as on the epidemiologic tracing of pregnancy outco
mes in circumstances where maternal need has dictated the administrati
on of a specific agent. Using these data, the US Food and Drug Adminis
tration has developed a fetal risk stratification system for individua
l agents as a guide for selection of therapy.