Urinary tract infection during pregnancy. Asymptomatic bacteriuria, acute cystitis, and acute pyelonephritis.

Urinary tract infection is one of the most common medical complications of pregnancy, occurring in roughly 10% of all pregnancies. The clinical entities most commonly seen are bacteriuria, acute cystitis, and acute pyelonephritis. Relative stasis of urine due to pregnancy-induced changes in the urinary tract is a significant causative factor. Escherichia coli is the most common responsible organism. Patients with untreated or inadequately treated asymptomatic bacteriuria are at high risk for development of acute pyelonephritis, a serious febrile illness that can lead to major maternal and fetal complications. Patients with acute pyelonephritis should be hospitalized and treated aggressively.