Screening and treatment of asymptomatic bacteriuria in pregnancy prevent pyelonephritis.

Although asymptomatic bacteriuria during pregnancy is associated with an increased risk of developing pyelonephritis, the effectiveness of screening programs to reduce this risk is controversial. A sharp reduction in the annual incidence of pyelonephritis (1.8% to 0.6%, P < .001) occurred after the introduction of a program to screen and treat asymptomatic bacteriuria among pregnant women followed at a large teaching hospital. The data provide retrospective and prospective evidence that screening and treatment programs for asymptomatic bacteriuria during pregnancy reduce the risk of pyelonephritis in a population with a moderate to high prevalence of bacteriuria.