The evidence regarding an association between the nitrofuran and sulfonamide classes of antibiotics and birth defects is mixed. As with all patients, antibiotics should be prescribed for pregnant women only for appropriate indications and for the shortest effective duration. During the second and third trimesters, sulfonamides and nitrofurantoins may continue to be used as first-line agents for the treatment and prevention of urinary tract infections and other infections caused by susceptible organisms. Prescribing sulfonamides or nitrofurantoin in the first trimester is still considered appropriate when no other suitable alternative antibiotics are available. Pregnant women should not be denied appropriate treatment for infections because untreated infections can commonly lead to serious maternal and fetal complications.