Bacteriuria during pregnancy may be classified as asymptomatic bacteriuria, infections of the lower urinary tract (cystitis), or infections of the upper urinary tract (pyelonephritis). Lower tract bacteriuria is associated with an increased risk of developing pyelonephritis in pregnancy, which is itself associated with adverse maternal and fetal outcomes. Pregnant women should be screened for the presence of bacteriuria early in pregnancy. All bacteriuria in pregnancy should be treated, and antimicrobial choice in pregnancy should reflect safety for both the mother and the fetus. After treatment of bacteriuria, patients should be followed closely due to risk of recurrent bacteriuria.